articles - explore the brain & spinal cord

Explore the Brain and Spinal Cord

Brain Basics

Higher Functions

Spinal CordPeripheral Nervous

System

The Neuron Sensory SystemsMethods and Techniques

Drug Effects

Neurological and Mental Disorders

Common questions about the brain and neuroscience

Another Day, Another Neuron

Questions/Answers from the "Neuroscientist Network"

First use of "neuro" words in recorded history

Women In Neuroscience

A Computer in Your Head?

A Career in Neuroscience: A Game of "Survivor?"

Jobs in Neuroscience

Milestones in Neuroscience Research

Nobel Prize Winners - Neuroscience

Neuroscience on Stamps

Neuroethics

Brain Basics

Divisions of the Nervous System

Divisions of the Brain

Our Divided Brain: Lobes of the Brain

Functional Divisions of the Cerebral Cortex

of 7Neuroscience for Kids - Explore the Nervous System

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The Brain "Right Down the Middle"

Brain Size/Cerebral Cortex

1 brain or 2? Split Brain Experiments

She Brains - He Brains

Brain Development

The Nervous System in Old Age

The Cranial Nerves

The Blood-Brain-Barrier

Your Brain's Home: The Skull

The Ventricles and CSF

The Meninges

Blood Supply of the Brain

How the Nervous System Interacts with Other Body Systems

Directions and Planes of Section

Compare the brains of 9 different species

More brains: comparative neuroanatomy

The Invertebrate Nervous System

The Brain during Sleep

How Much do Animals Sleep?

Brain Fitness - Your Guide to Good Brain Health

Disorders of the Brain

"Higher" Functions

Chocolate and the Nervous System

Do We Use Only 10% of our Brain?


Laughter and the Brain

Oh Say Can You Say...The Brain and Language

Nutrition and the Brain

"Smart" Drugs?

The Musical Brain

The Brain vs. The Computer

What Became of Albert Einstein's Brain?

Eugene O'Neill: What Went Wrong?

Yawning: Why We Yawn and Why They are "Contagious"

Moonstruck: Does the Full Moon Influence Behavior?

Synesthesia

Brain "Plasticity": Learning and Memory

Face Recognition

The Spinal Cord

Our Divided Spinal Cord: Segments of the Spinal Cord

The Knee Jerk Reflex (monosynaptic reflex)

The Peripheral Nervous System

The Autonomic Nervous System

The Neuron

Millions and Billions of Cells: Types of Neurons

Making Connections: The Synapse


Gallery of Neurons

The Sounds of Neuroscience

The Synapse - Up Close and Personal

Lights, Camera, Action Potential

Glia: The Forgotten Brain Cell

Dangerous Chemicals: Neurotoxins - Source and Effect

Neurotransmitters and Neuroactive Peptides

Chemical Weapons: Nerve Agents

Conduction Velocity

Salty What? Saltatory Conduction

Sensory Systems The Skin and its Sensory Receptors

Pain and Why it Hurts

The Tooth

I Spy...The Eye

The Retina

The Visual Pathway

Do you wear glasses? Find out why!

Eye Safety Tips

Hear Ye, Hear Ye - The Ear

How the Nose Knows - The Nose

That's Tasty!

Does the COLOR of Foods and Drinks Affect Their Taste?

Amazing Animals Senses


Neuroscience Methods and Techniques Statistics: By the Numbers

The 10-20 System of Electrode Placement (for the EEG)

Common Methods Used in Neuroscience Research

Brain Imaging Methods

Glossary of Neuroscience Words

Careers in Neuroscience

The Effects of Drugs on the Nervous System

Alcohol Amphetamines

Barbiturates Caffeine

Cocaine Ecstasy

Heroin Inhalants

LSD Marijuana

Nicotine Rohypnol

1,4-Butanediol PCP

GHB Hallucinogenic Mushrooms


Alzheimer's Disease Amyotrophic Lateral Sclerosis

Asperger's Syndrome Attention Deficit Hyperactivity Disorder

Autism Bacterial Meningitis

Bipolar Disorder Common Eye Diseases and Disorders


Dyslexia - I Dyslexia - II

Epilepsy Fetal Alcohol Syndrome

Gulf War Syndrome Huntington's Disease

Lead and the Nervous System Lyme Disease

Mercury and the Nervous System Multiple Sclerosis

Narcolepsy Polio

Rabies Restless Legs Syndrome

Schizophrenia Soccer and the Brain (Heading for Injury?)

Spina Bifida Stroke

Tourette Syndrome Transient Ischemic Attack

West Nile Virus


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Kids


Adventures in Neuroanatomy: Parts of the Nervous System

Contents of this Page Central Nervous

System

Peripheral Nervous System


Brain Structures

Brain Structure Poll

Neuroanatomy: the structure of the nervous system. To learn how

the nervous system functions, you must learn how the nervous system is put together.

The nervous system can be divided into several connected systems that function together. Let's start with a simple division:

The Nervous System is divided into:

The Central Nervous System and the Peripheral Nervous System

Let's break the central nervous system and the peripheral nervous system into more parts.

Central Nervous System

The central nervous system is divided into two parts: the brain and

the spinal cord. The average adult human brain weighs 1.3 to 1.4 kg

(approximately 3 pounds). The brain contains about 100 billion nerve cells (neurons) and trillons of "support cells" called glia. The spinal cord is about 43 cm long in adult women and 45 cm long in adult men and weighs about 35-40 grams. The vertebral column, the collection of bones (back bone) that houses the spinal cord, is about 70 cm long. Therefore, the spinal cord is much shorter than the vertebral column.

For brain weights of other animals, see brain facts and figures.

The Central Nervous System

(Brain and Spinal Cord)

Did you know?

A stegosaurus dinosaur weighed approximately 1,600 kg but had a brain that weighed only approximately 70 grams (0.07 kg). Therefore, the brain was only 0.004% of its total body weight. In contrast, an adult human weighs approximately 70 kg and has a brain that weighs approximately 1.4 kg. Therefore, the human brain is about 2% of the total body weight. This makes the brain to body ratio of the human 500 times greater than that of the stegosaurus. See "My Brain is Bigger than Your Brain" for more about brain size.

Page 1 of 8Neuroscience for Kids - Divisions of the NS

Peripheral Nervous System

The peripheral nervous system is divided into two major parts: the somatic nervous system and the autonomic nervous system.

1. Somatic Nervous System

The somatic nervous system consists of peripheral nerve fibers that send sensory information to the central nervous system AND motor nerve fibers that project to skeletal muscle.

The picture on the left shows the somatic motor system. The cell body is located in either the brain or spinal cord and projects directly to a skeletal muscle.

2. Autonomic Nervous System

The autonomic nervous system is divided into three parts: the sympathetic nervous system, the parasympathetic nervous system and the enteric nervous system. The autonomic nervous system controls smooth muscle of the viscera (internal organs) and glands.

This picture shows the general organization of the autonomic nervous system. The preganglionic neuron is located in either the

brain or the spinal cord. This preganglionic neuron projects to an autonomic ganglion. The postganglionic neuron then projects to the target organ.

Notice that the somatic nervous system has only one neuron between the central nervous system and the target organ while the autonomic nervous system uses two neurons.

The enteric nervous system is a third division of the autonomic nervous system that you do not hear much about.

The enteric nervous system is a meshwork of nerve fibers that innervate the viscera (gastrointestinal tract, pancreas, gall bladder).

The following table shows how the nervous system can be divided. The bottom row of the table contains the names of specific areas within the brain.

Click on any word in the bottom two rows to hear how the term is pronounced. These are ".wav" files (about 10k each).


Click on a word to hear how it is pronounced. These are "wav" files.

Check out the glossary for definitions of these brain areas.


Here is a quick look at one way to divide the brain.

Telencephalon

Diencephalon

Mesencephalon

Metencephalon

Myelencephalon

Hear IT!Amygdala

Basal Ganglia

CerebellumCerebral Cortex

Diencephalon

Hippocampus Hypothalamus Medulla Mesencephalon Metencephalon

Myelencephalon Pons Tectum Tegmentum Telencephalon Thalamus

From a top view, notice how the brain is divided into two halves, called hemispheres. Each hemisphere communicates with the other through the


In the Peripheral Nervous System, neurons can be functionally divided in 3 ways:

corpus callosum, a bundle of nerve fibers. (Another smaller fiber bundle that connects the two hemispheres is called the anterior commissure).

Hear IT!

Cerebral Cortex

CerebellumCorpus Callosum

Some differences between the Peripheral Nervous System (PNS) and the Central Nervous System (CNS):

1. In the CNS, collections of neurons are called nuclei.

In the PNS, collections of neurons are called ganglia.

2. In the CNS, collections of axons are called tracts.

In the PNS, collections of axons are called nerves.

1Sensory (afferent) � carry information INTO the central nervous system from sense organs.

OR

Motor (efferent) � carry information away from the central nervous system (for muscle


control).

2Cranial � connects the brain with the periphery.

OR

Spinal � connects the spinal cord with the periphery.

3Somatic � connects the skin or muscle with the central nervous system.

OR

Visceral � connects the internal organs with the central nervous system.

Brain Structures

Cerebral Cortex

Functions:

� Thought

� Voluntary movement

� Language

� Reasoning

� Perception

The word "cortex" comes from the Latin word for "bark" (of a tree). This is because the cortex is a sheet of tissue that makes up the outer layer of the brain. The thickness of the cerebral cortex varies from 2 to 6 mm. The right and left sides of the cerebral cortex are connected by a thick band of nerve fibers called the "corpus callosum." In higher mammals such as humans, the cerebral cortex looks like it has many bumps and grooves. A bump or bulge on the cortex is called a gyrus (the plural of the word gyrus is "gyri") and a groove is called a sulcus (the plural of the word sulcus is "sulci"). Lower mammals, such as rats and mice, have very few gyri and sulci.

Cerebellum

Functions:

� Movement

� Balance

� Posture

The word "cerebellum" comes from the Latin word for "little brain." The cerebellum is located behind the brain stem. In some ways, the cerebellum is similar to the cerebral cortex: the cerebellum is divided into hemispheres and has a cortex that surrounds these hemispheres.

Brain stem

Functions:

� Breathing

� Heart Rate

� Blood Pressure

The brain stem is a general term for the area of the brain between the thalamus and spinal cord. Structures within the brain stem include the medulla, pons, tectum, reticular formation and tegmentum. Some of these areas are responsible for the most basic functions of life such as breathing, heart rate and blood pressure.

Hypothalamus

Functions: The hypothalamus is composed of several different areas and is located at the base of the brain. Although it is the size of only a pea (about 1/300 of


� Body Temperature

� Emotions

� Hunger

� Thirst

� Circadian Rhythms

the total brain weight), the hypothalamus is responsible for some very important functions. One important function of the hypothalamus is the control of body temperature. The hypothalamus acts as a "thermostat" by sensing changes in body temperature and then sending signals to adjust the temperature. For example, if you are too hot, the hypothalamus detects this and then sends a signal to expand the capillaries in your skin. This causes blood to be cooled faster. The hypothalamus also controls the pituitary.

Thalamus

Functions:

� Sensory processing

� Movement

The thalamus receives sensory information and relays this information to the cerebral cortex. The cerebral cortex also sends information to the thalamus which then transmits this information to other areas of the brain and spinal cord.

Limbic System

Functions:

� Emotions

The limbic system (or the limbic areas) is a group of structures that includes the amygdala, the hippocampus, mammillary bodies and cingulate gyrus. These areas are important for controlling the emotional response to a given situation. The hippocampus is also important for memory.

Hippocampus

Functions:

� Learning

� Memory

The hippocampus is one part of the limbic system that is important for memory and learning.

Basal Ganglia

Functions:

� Movement

The basal ganglia are a group of structures, including the globus pallidus, caudate nucleus, subthalamic nucleus, putamen and substantia nigra, that are important in coordinating movement.

Midbrain

Functions:

� Vision

� Audition

� Eye Movement

� Body Movement

The midbrain includes structures such as the superior and inferior colliculi and red nucleus. There are several other areas also in the midbrain.


Now that you have read about many of the areas of the brain, here is where some of these areas are located:

Check out the glossary for definitions of other brain areas.

Travel through the brain with the incredible Brain Fly-Through game. (Requires the FLASH plug-in for your browser.)

Did you know?

John Adams (2nd President of the US) and his son, John Quincy Adams (6th President of the US), were both born

in Braintree, Massachusetts.

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Exploring the Nervous System

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Not enough detail for you? Here is another table showing more brain structures and their associated divisions. The roman numerals (I through XII) refer to the cranial nerves.


The brain can be separated into phylogenetic (through evolution) and embryological (through development) divisions. Below are two tables that show how the brain can be divided - do not get caught up in the terminology - these are just names for specific areas of the brain. "Divisions of the Nervous System" discusses the functions of many of these areas.


Major Division Subdivision Structures

Prosencephalon (Forebrain)

TelencephalonNeocortex; Basal Ganglia; Amygdala; Hippocampus;

Lateral Ventricles

DiencephalonThalamus; Hypothalamus; Epithalamus; Third

Ventricle

Mesencephalon (Midbrain)

Mesencephalon Tectum; Tegmentum; Cerebral Aqueduct

Rhombencephalon (Hindbrain)

Metencephalon Cerebellum; Pons; Fourth Ventricle

Myelencephalon Medulla Oblongata; Fourth Ventricle


Page 1 of 4Neuroscience for Kids - Brain Divisions

External Landmarks

Internal Landmarks

Major Nuclei Major Fiber Tracts

Ventricles

Telencephalon

Gyri and sulci

Olfactory Nerve (I)

Cerebral Cortex

Amygdala

Hippocampus

Basal Ganglia

� Caudate

nucleus

� Putamen

� Globus

Pallidus

� Claustrum

Internal Capsule

Corpus Callosum

Anterior Commissure

Lateral Ventricles

Interventricular Foramen

Diencephalon

Infundibulum

Optic Nerve (II)

Optic Chiasm

Mammillary bodies

Thalamus

Hypothalamus

Fornix

Mammillo-thalamic Tract

Third Ventricle

Mesencephalon (Midbrain)

Superior Colliculus

Inferior Colliculus

Cerebral Peduncles

Substantia Nigra

Central Gray

Red Nucleus

Crus Cerebri

Cerebral Aqueduct


Oculomotor Nerve (III)

Trochlear Nerve (IV)

Metencephalon

Pons

Cerebellum

Trigeminal Nerve (V)

Abducens Nerve (VI)

Facial Nerve (VII)

Vestibulocochlear Nerve (VIII)

Pontine Nuclei

Deep Cerebellar Nuclei

Fornix


Fourth Ventricle

Myelencephalon

Medulla

Glossopharyngeal Nerve (IX)

Vagus Nerve (X)

Spinal Accessory Nerve (XI)

Hypoglossal Nerve (XII)

Inferior Olive Pyramids


Fourth Ventricle

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Donate to

Neuroscience for Kids


Explore the Brain and Spinal Cord

Brain Basics

Higher Functions

Spinal CordPeripheral Nervous

System

The Neuron Sensory SystemsMethods and Techniques

Drug Effects


Common questions about the brain and neuroscience

Another Day, Another Neuron

Questions/Answers from the "Neuroscientist Network"

First use of "neuro" words in recorded history

Women In Neuroscience

A Computer in Your Head?

A Career in Neuroscience: A Game of "Survivor?"

Jobs in Neuroscience

Milestones in Neuroscience Research

Nobel Prize Winners - Neuroscience

Neuroscience on Stamps

Neuroethics

Brain Basics



Our Divided Brain: Lobes of the Brain


Page 1 of 7Neuroscience for Kids - Explore the Nervous System

The Brain "Right Down the Middle"

Brain Size/Cerebral Cortex

1 brain or 2? Split Brain Experiments


Brain Development


The Cranial Nerves

The Blood-Brain-Barrier

Your Brain's Home: The Skull

The Ventricles and CSF

The Meninges

Blood Supply of the Brain

How the Nervous System Interacts with Other Body Systems


Compare the brains of 9 different species

More brains: comparative neuroanatomy

The Invertebrate Nervous System

The Brain during Sleep

How Much do Animals Sleep?

Brain Fitness - Your Guide to Good Brain Health

Disorders of the Brain

"Higher" Functions

Chocolate and the Nervous System

Do We Use Only 10% of our Brain?


Laughter and the Brain

Oh Say Can You Say...The Brain and Language

Nutrition and the Brain

"Smart" Drugs?

The Musical Brain

The Brain vs. The Computer

What Became of Albert Einstein's Brain?

Eugene O'Neill: What Went Wrong?

Yawning: Why We Yawn and Why They are "Contagious"

Moonstruck: Does the Full Moon Influence Behavior?

Synesthesia

Brain "Plasticity": Learning and Memory

Face Recognition

The Spinal Cord

Our Divided Spinal Cord: Segments of the Spinal Cord

The Knee Jerk Reflex (monosynaptic reflex)

The Peripheral Nervous System

The Autonomic Nervous System

The Neuron

Millions and Billions of Cells: Types of Neurons

Making Connections: The Synapse


Gallery of Neurons

The Sounds of Neuroscience

The Synapse - Up Close and Personal

Lights, Camera, Action Potential

Glia: The Forgotten Brain Cell

Dangerous Chemicals: Neurotoxins - Source and Effect

Neurotransmitters and Neuroactive Peptides

Chemical Weapons: Nerve Agents

Conduction Velocity

Salty What? Saltatory Conduction

Sensory Systems The Skin and its Sensory Receptors

Pain and Why it Hurts

The Tooth

I Spy...The Eye

The Retina

The Visual Pathway

Do you wear glasses? Find out why!

Eye Safety Tips

Hear Ye, Hear Ye - The Ear

How the Nose Knows - The Nose

That's Tasty!

Does the COLOR of Foods and Drinks Affect Their Taste?

Amazing Animals Senses


Neuroscience Methods and Techniques Statistics: By the Numbers

The 10-20 System of Electrode Placement (for the EEG)

Common Methods Used in Neuroscience Research

Brain Imaging Methods

Glossary of Neuroscience Words

Careers in Neuroscience

The Effects of Drugs on the Nervous System

Alcohol Amphetamines

Barbiturates Caffeine

Cocaine Ecstasy

Heroin Inhalants

LSD Marijuana

Nicotine Rohypnol

1,4-Butanediol PCP

GHB Hallucinogenic Mushrooms


Alzheimer's Disease Amyotrophic Lateral Sclerosis

Asperger's Syndrome Attention Deficit Hyperactivity Disorder

Autism Bacterial Meningitis

Bipolar Disorder Common Eye Diseases and Disorders


Dyslexia - I Dyslexia - II

Epilepsy Fetal Alcohol Syndrome

Gulf War Syndrome Huntington's Disease

Lead and the Nervous System Lyme Disease

Mercury and the Nervous System Multiple Sclerosis

Narcolepsy Polio

Rabies Restless Legs Syndrome

Schizophrenia Soccer and the Brain (Heading for Injury?)

Spina Bifida Stroke

Tourette Syndrome Transient Ischemic Attack

West Nile Virus


[Table of Contents]

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Kids



The cerebral cortex is responsible for many "higher�order" functions like language and

information processing. Language centers are usually found only in the left cerebral hemisphere. For more information on language and differences between the right and left cerebral hemisphere, read about split brain experiments.

Cortical Area Function

Broca's Area

Wernicke's Area

Prefrontal CortexProblem Solving, Emotion, Complex Thought

Motor Association Cortex

Coordination of complex movement

Primary Motor Cortex Initiation of voluntary movement

Primary Somatosensory Cortex

Receives tactile information from the body

Sensory Association AreaProcessing of multisensory information

Visual Association AreaComplex processing of visual information

Visual Cortex Detection of simple visual stimuli

Page 1 of 2Neuroscience for Kids - Functional Divisions

Wernicke's Area Language comprehension

Images courtesy of Slice of Life.

Auditory Association Area

Complex processing of auditory information

Auditory CortexDetection of sound quality (loudness, tone)

Speech Center (Broca's Area)

Speech production and articulation

Take the Cerebral Cortex Review Test. Requires the Adobe Acrobat

Reader.

Answers to the test.

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Page 2 of 2Neuroscience for Kids - Functional Divisions

The Brain: Right down the

Middle

Although some people may think that the brain is like a

bowl of jell�O, the brain is NOT a bowl of jell�O.

Unlike a bowl of jell�O, the brain is not a uniform

material. Rather, the brain is made up of many different areas, each having a particular structure and function. To separate the brain into right and left hemispheres, you need to cut the brain in the "midsagittal plane".

Midsaggital Plane

Only some of the structures that are visible on a real brain have been labeled.

Brain Structures

Page 1 of 3Neuroscience for Kids - Middle

Cerebral Cortex

Functions:

� Thought

� Voluntary

movement

� Language

� Reasoning

� Perception

The word "cortex" comes from the Latin word for "bark" (of a tree). This is because the cortex is a sheet of tissue that makes up the outer layer of the brain. The thickness of the cerebral cortex varies from 2 to 6 mm. The right and left sides of the cerebral cortex are connected by a thick band of nerve fibers called the "corpus callosum". In higher mammals like humans, the cerebral cortex looks like it has many bumps and grooves. A bump or bulge on the cortex is called a gyrus (the plural of the word gyrus is "gyri") and a groove is called a sulcus (the plural of the word sulcus is "sulci"). Lower mammals like rats and mice have very few gyri and sulci.

Cerebellum

Functions:

� Movement

� Balance

� Posture

The word "cerebellum" comes from the Latin word for "little brain". The cerebellum is located behind the brain stem. In some ways, the cerebellum is a bit like the cerebral cortex: the cerebellum is divided into hemispheres and has a cortex that surrounds these hemispheres.

Brain stem

Functions:

� Breathing

� Heart Rate

� Blood

Pressure

The brain stem is a general term for the area of the brain between the thalamus and spinal cord. Structures within the brain stem include the medulla, pons, tectum, reticular formation and tegmentum. Some of these areas are responsible for the most basic functions of life such as breathing, heart rate and blood pressure.

Hypothalamus

Functions:

� Body

Temperature

� Emotions

� Hunger

� Thirst

� Circadian

Rhythms

The hypothalamus is composed of several different areas and is located at the base of the brain. It is only the size of a pea (about 1/300 of the total brain weight), but it is responsible for some very important behaviors. One important function of the hypothalamus is the control of body temperature. The hypothalamus acts as like a "thermostat" by sensing changes in body temperature and then sending out signals to adjust the temperature. For example, if you are too hot, the hypothalamus detects this and then sends out a signal to expand the capillaries in your skin. This causes blood to be cooled faster. The hypothalamus also controls the pituitary.

Thalamus


Check out the glossary for definitions of other brain areas.

Functions:

� Sensory

Integration

� Motor

Integration

The thalamus receives sensory information and relays this information to the cerebral cortex. The cerebral cortex also sends information to the thalamus which then transmits this information to other areas of the brain and spinal cord.

Hear IT!

CerebellumCorpus Callosum

Cortex Hypothalamus Thalamus

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The Cerebral Cortex

(or "My Brain is Bigger than Your Brain")

As you might imagine, larger animals have larger brains. However, this does not mean that animals with larger brains are smarter than animals with smaller brains. For example, a larger brain is necessary to control larger muscles in larger animals and a larger brain is necessary to process more sensory information from the skin in larger animals - this has nothing to do with intelligence.

Brain Weight(gm)

Species

6,000

Elephant

1,300-1,400Adult Human

97Rhesus Monkey

72Dog

30

Cat

10Rabbit

2.2Owl

More brain weights

During the course of evolution, the brain areas that show the most changes are the cerebral hemispheres (the red areas in the figure): the more recently evolved animals have a larger proportion of the brain taken up by the cerebral cortex. In the "higher" animals (especially the higher mammals), the surface of the cerebral cortex becomes folded. This creates grooves on the surface of the brain called "sulci" (singular = "sulcus"). The bumps or ridges

Page 1 of 4Neuroscience for Kids - Brain Size

on the surface of the brain are called "gyri" (singular = "gyrus"). The folding of the cortex increases the cortical surface area. The cerebral cortex, made up of four lobes is involved in many complex brain functions including memory, perceptual awareness, "thinking", language and consciousness.

(Brains drawn to about the same scale)

Hear IT!

Gyri Gyrus Sulcus Sulci

The Primary Somatosensory Cortex

Parts of the cerebral cortex in the parietal lobe are involved with processing information related to touch. One such area is the primary somatosensory cortex which is located behind the central sulcus. Neurons in the primary somatosensory are activated when the skin is touched. However, the body is NOT represented in the cortex in proportion to the amount of skin. A map of the human somatosensory cortex was drawn by Dr. Wilder Penfield, a neurosurgeon, in the 1950's. After stimulating the


cortex of patients undergoing brain surgery for epilepsy, Dr. Penfield asked the patients what they felt. By observing the location on the brain that caused patients to feel sensations on different parts of their bodies, Dr. Penfield was able to draw a map of the brain. As you can see in this figure above, even though the arms and trunk make up most of your body, they are not given much cortical tissue. However, the face and hands take up a good portion of the primary somatosensory cortex. This is because the amount of primary somatosensory cortex is directly related to the sensitivity of a body area and the density of receptors found in different parts of the body. The areas of skin with the higher density of receptors (like the face, hands and fingers) have more cortical tissue devoted to them. If you were "built" in proportion to the amount of cortex devoted to each part of your body, you would look a bit distorted: you would have a big head and hands and a small torso and tiny legs. This distorted body map is called a homunculus which means "little man".

Think about how sensitive your fingertips are compared to your leg. For a demonstration of the sensitivity of different body areas, test your two point discrimination.

Hear IT!

Homunculus

Try the REALLY WEIRD BODY MAP animation to learn more about the homunculus. Requires

the shockwave plug�in for your browser.

Why don't you probe the motor cortex with this science odyssey activity from PBS. Requires the

shockwave plug�in for your browser.

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Experiments


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1��One Brain...or Two?��2

Left

Hemisphere

How many brains do you have � one or two?

Actually, this is quite easy to answer...you have only one brain. However, the cerebral hemispheres are divided right down the middle into a right hemisphere and a left hemisphere. Each hemisphere appears to be specialized for some behaviors. The hemispheres communicate with each other

through a thick band of 200�250 million

nerve fibers called the corpus callosum. (A

smaller band of nerve fibers called the anterior commissure also connects parts of the cerebral hemispheres.)

Right

Hemisphere

Handedness

Are you right�handed or left�handed? As you probably know,

most people (about 90% of the population) are right�handed � they

prefer to use their right hand to write, eat and throw a ball. Another way to refer to people who use their right hand is to say that they are "right hand

dominant." It follows that most of the other 10% of the population is left�handed or "left hand

dominant." There are few people who use each hand equally; they are "ambidextrous." (Most people also have a dominant eye and dominant ear...test your "sidedness" here.)

Exactly why people are right�handed or left�handed is somewhat of a mystery. Dr.

William Calvin has developed a fascinating theory about the origin of handedness and has written an essay called The Throwing Madonna to explain it.

Right Side �

Left Side

The right side of the brain controls muscles on the left side of the body and the left side of the

Page 1 of 6Neuroscience for Kids - Hemispheres

brain controls muscles on the right side of the body. Also, in general, sensory information from the left side of the body crosses over to the right side of the brain and information from the right side of the body crosses over to the left side of the brain. Therefore, damage to one side of the brain will affect the opposite side of the body.

In 95% of right�handers,

the left side of the brain is dominant for language.

Even in 60�70% of left�

handers, the left side of brain is used for language. Back in the 1860s and 1870s, two neurologists (Paul Broca and Karl Wernicke) observed that people who had damage to a particular area on the left side of the brain had speech and language problems. People with damage to these areas on the right side usually did not have any language problems. The two language areas of the brain that are important for language now bear their names: Broca's area and Wernicke's area.

Broca's Area

Wernicke's Area

Images courtesy of Slice of Life.

Left Hemisphere

Cerebral Dominance

Each hemisphere of the brain is dominant for other

Right Hemisphere


� Language

� Math

� Logic

behaviors. For example, it appears that the right brain is dominant for spatial abilities, face recognition, visual imagery and music. The left brain may be more dominant for calculations, math and logical abilities. Of course, these are generalizations and in normal people, the two hemispheres work together, are connected, and share information through the corpus callosum. Much of what we know about the right and left hemispheres comes from studies in people who have had the corpus callosum split - this surgical operation isolates most of the right hemisphere from the left hemisphere. This type of surgery is performed in patients suffering from epilepsy. The corpus callosum is cut to prevent the spread of the "epileptic seizure" from one hemisphere to the other.

� Spatial

abilities

� Face

recognition

� Visual

imagery

� Music

Split-Brain Experiments

Roger Sperry (who won the Nobel prize in 1981) and Michael Gazzaniga are two neuroscientists who studied patients who had surgery to cut the corpus callosum.

These studies are called "Split-Brain Experiments". After surgery, these

people appeared quite "normal" - they could walk, read, talk, play sports and do all the everyday things they did before surgery. Only after careful experiments that isolated information from reaching one hemisphere, could the real effects of

the surgery be determined.

Dr. Sperry used a tachistoscope to present visual information to one hemisphere or the other. The tachistoscope requires people to focus on a point in the center of their visual field. Because each half of the visual field projects to the opposite site of the brain (crossing in the optic chiasm), it is possible to project a picture to either the right hemisphere OR the left hemisphere.

So, say a "typical" (language in the LEFT hemisphere) split-brain patient is sitting down, looking straight ahead and is focusing on a dot in the middle of a screen. Then a picture of a spoon is flashed to the right of the dot. The visual information about the spoon crosses in the optic chiasm and ends up in the LEFT HEMISPHERE. When the person is asked what the picture was, the person has no problem identifying the spoon and says "Spoon." However, if the spoon had been flashed to the left of the dot (see the picture), then the visual information would have traveled to the RIGHT HEMISPHERE. Now if the person is asked what the picture was, the person will say that nothing


was seen!! But, when this same person is asked to pick out an object using only the LEFT hand, this person will correctly pick out the spoon. This is because touch information from the left hand crosses over to the right hemisphere - the side that "saw" the spoon. However, if the person is again asked what the object is, even when it is in the person's hand, the person will NOT be able to say what it is because the right hemisphere cannot "talk." So, the right hemisphere is not stupid, it just has little ability for language - it is "non-verbal."

Another type of experiment performed with split brain patients uses chimeric figures, like this one to the right. In this figure, the face on the left is a woman and the face on the right is a man. Therefore, if the patient focuses on the dot in the middle of the forehead, the visual information about the woman's face will go to the right cerebral hemisphere and information about the man's face will go to the left hemisphere. When a split brain patient is asked to point to a whole, normal picture of the face that was just seen, the patient will usually pick out the woman's picture (remember, the information about the woman's face went to the RIGHT cerebral hemisphere). However, if the patient is required to say whether the picture was a man or a woman, the patient will SAY that the picture was of a man. Therefore, depending on what the patient is required to do, either the right or left hemisphere will dominate. In this case, when speech is not required, the right hemisphere will dominate for recognition of faces.

Before different types of brain surgery, it is important to identify which cerebral hemisphere is dominant for language so that the neurosurgeon can avoid damaging speech areas. One way to test which hemisphere is dominant for language is with a procedure called the Wada Test. During this test, a fast acting anesthetic called sodium amytal (amobarbital) is injected into the right or left carotid artery. The right artery supplies the right cerebral hemisphere and the left artery supplies the left cerebral hemisphere. Therefore, either the right or left hemisphere can be "put to sleep" temporarily. If the left hemisphere is put to sleep in people who


have language ability in the left hemisphere, then when asked to speak, they cannot. However, if the right hemisphere is put to sleep, then these people will be able to speak and answer questions. (Remember too that because the right hemisphere controls muscles on the left side, people will not be able to move the left side of their bodies.)

Another way to test for language representation in the brain is to electrically stimulate the cerebral cortex. A neurosurgeon can place an electrode on various areas of the exposed brain of an awake patient during surgery. The patient can say what he or she feels and thinks. Placement of the electrode on the brain does NOT hurt because the brain itself does not have any receptors for pain. In people who have left side dominance for language, electrical stimulation of various locations on the left cerebral cortex will interfere with speech.

A great page on split brain experiments can be found at Macalester University. There are also

several other pages with more information on split�brain experiments and handedness and brain

lateralization.

Play the Split Brain Experiments Game from the Nobel e�Museum.

Are you one of the few left handers? Well, then you have something in common with some famous people that include Bill Clinton, Jimmy Connors, and Marilyn Monroe. For information all about left

handedness, see Lorin's Left�handedness Site. If you are interested in seeing some pictures of the

cerebral hemispheres, the Virtual Hospital has some great images.

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Bigger - Stronger - Faster...are there really any differences between female brains and male brains? Differences between the brains of men and women have generated considerable scientific and public interest. If there are differences in the way that men and women behave, then it is reasonable to suppose that their brains have something to do these behavioral differences. Just what are these differences and where in the brain might these differences be located?

For hundreds of years, scientists have searched for differences between the brains of men and women. Early research showing that male brains were larger than female brains was used to "prove" that male brains were superior

to female brains. Of course, this "proof" is NOT so simple and straight

forward as you will see. Nevertheless, even today, there is plenty of controversy about the differences in the brains of men and women. Not only from an anatomical point of view, but also from a functional point of view - in other words, just what do the differences in the brains mean?

Hormones that are present during a baby's development will affect the brain and determine whether the brain will be female or male. Studies that have looked at differences in the brains of males and females have focused on:

1. Total Brain Size

2. The Corpus Callosum

3. The Hypothalamus

Differences in Total Brain Size?

Almost all studies show that at birth, a boy's brain is bigger than a girl's brain. At birth, the average brain of boys is between 12-20% larger than that of girls. The head circumference of boys is also larger (2%) than that of girls. However, when the size of the brain is compared to body weight at this age, there is almost no difference between boys and girls. So, a girl baby and a Brain Weights

Page 1 of 4Neuroscience for Kids - He-She

boy baby who weigh the same will have similar brain sizes.

In adults, the average brain weight in men is about 11-12% MORE than the average brain weight in women. Men's heads are also about 2% bigger than women's. Remember though, men on average weigh more than women and that absolute brain size may not be the best measure of intelligence. Many behavioral differences have been reported for men and women. For example, it has been said that women are better in certain language abilities and men are better in certain spatial abilities. Many studies have tried to find differences in the right and left cerebral hemispheres to suggest that male and female brains are different. However, few of these experiments have found meaningful differences between men and women. If fact, there are many similarities between the cerebral hemispheres of men and women.

(Data from Dekaban, A.S. and Sadowsky, D., Changes in brain weights during the span of human life: relation of brain weights to body heights and body weights, Ann. Neurology, 4:345-356, 1978)

Differences in the Corpus Callosum?

The major pathway that connects the right and left cerebral hemispheres is called the corpus callosum. (The corpus callosum is the fiber tract made up of 200-250 million axons that is cut in split brain patients.) Some claims have been made that the corpus callosum is bigger and more developed in women than in men. These claims

have even been reported in the popular media (Time Magazine, Jan. 20,


1992, pp. 36-42; Newsweek Magazine, March 27, 1995, pp. 51). However, other studies have told a different story. Using magnetic resonance imaging methods, some researchers have found no differences in the size of the corpus callosum in men and women. Further research that compares the size of the corpus callosum size in men and women is needed.

Differences in the Hypothalamus?

The hypothalamus is one area of the brain with well-documented differences between men and women. Two areas of the hypothalamus, the preoptic area and the suprachiasmatic nucleus, have clear differences in female and male brains.

Preoptic Area of the Hypothalamus This area of the hypothalamus is involved in mating behavior. In males of several species including humans, the preoptic area is greater in volume, in cross-sectional area and in the

number of cells. In men, this area is about 2.2 times larger than in women and contains 2 times more cells. Apparently, the difference in this area is only apparent after a person is 4 years old. At 4 years of age, there is a decrease in the number of cells in this nucleus in girls. The exact function of this nucleus in behavior is not fully known.

Suprachiasmatic Nucleus of the Hypothalamus This area of the hypothalamus is involved with circadian rhythms and reproduction cycles. The only difference between women and men in this area is one of shape: in males, this nucleus is shaped like a sphere; in females it is more elongated. However, the number of cells and volume of this nucleus are not different in men and women. It is possible that the shape of the suprachiasmatic nucleus influences the connections that this area makes with other areas of the brain, especially the other areas of the hypothalamus.

Women and Men � Boys and Girls

The behavioral and neurological differences between men and women require further study. Perhaps new studies will find neuroanatomical differences that explain some of the complex differences between male and female behavior. However, from a review of the current scientific evidence, it appears that differences in many cognitive behaviors (for example, memory) are related more to individual differences between people than to whether people are female or male.

Hear IT!

HypothalamusCorpus Callosum


More about the possible differences between male and female brains:

� Beyond the gender myths � from Time Magazine, 1998

� Brain imaging study of spatial memory

� Gender and the Brain from the Society for Neuroscience

� Gender Differences Found In The Way Boys And Girls Solve Math Problems

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Brain Development

The brain grows at an amazing rate during development. At times during

brain development, 250,000 neurons are added every minute!! At birth,

almost all the neurons that the brain will ever have are present. However, the brain continues to grow for a few years after birth. By the age of 2 years old, the brain is about 80% of the adult size.

You may wonder, "How does the brain continue to grow, if the brain has most of the neurons it will get when you are born?". The answer is in glial

cells. Glia continues to divide and multiply. Glia carries out many important functions for normal brain function including insulating nerve cells with myelin. The neurons in the brain also make many new connections after birth.

The Brain During Development

The nervous system develops from embryonic tissue called the ectoderm. The first sign of the developing

nervous system is the neural plate that can be seen at about the 16th

day of development. Over the next few

days, a "trench" is formed in the neural plate - this creates a neural groove. By the 21st

day of development,

a neural tube is formed when the edges of the neural groove meet. The rostral (front) part of the neural tubes goes on to develop into the brain and the rest of the neural tube develops into the spinal cord. Neural crest cells become the peripheral nervous system.

At the front end of the neural tube, three major brain areas are formed: the prosencephalon (forebrain), mesencepalon (midbrain) and rhombencephalon (hindbrain). By the 7th week of development, these three areas divide again. This process is called encephalization.

Average brain weights at different times of development:

AGE BRAIN WEIGHT (grams)

20 weeks of gestation 100

Page 1 of 3Neuroscience for Kids - Brain Development

Birth 400

18 months old 800

3 years old 1100

Adult 1300�1400

Brain Weight

The top graph on the left shows the brain weights of males and females at different ages. The bottom graph shows the brain weight to total body weight ratio (expressed as a percentage). The adult brain makes up about 2% of the total body weight.

(Data from Dekaban, A.S. and Sadowsky, D., Changes in brain weights during the span of human life: relation of brain weights to body heights and body weights, Ann. Neurology,

4:345�356, 1978)


More about Brain Development

� The Teen Brain � Online Newshour (October 13, 2004)

� Embryological Development of the Human Brain

� Society for Neuroscience

� Brain reorganization

� Neuron migration

� Axon guidance

� Visual development

� Brain work�outs

� Child abuse and the brain

� Parental care and the brain

� Secret Life of the Brain � a PBS special exploring the brain from

birth to old age

� Child Development Articles � from BrainConnection.com

� Baby Talk � Learning Language � from US News and World

Report, June 15, 1998

� Development and Neurobiology Column

� Understanding TV's effects on the developing brain

� The TEEN Brain � articles from US News and World Report

(August 9, 1999). Some of these articles are available on�line.

� Inside the Teenage Brain � PBS

� Zero to Three � BrainWonders

� The brain during old age

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Over the last 100 years there has been a dramatic increase in the population of elderly (age 65 years and older) people. As shown in the graph, elderly people in the US made up only 4.1% of the population in 1900, but 8.1% in 1950 and 12.8% in 1995. By 2050, it is estimated that 20% of the

population will be 65 years old or older. This increase in the elderly population and the high incidence of age-related neurological disorders make it important to understand how the human brain ages.

To investigate the changes that the brain undergoes during aging, neuroscientists use brain imaging methods to observe the anatomy and physiology of the living brain. Scientists can also study autopsy specimens to investigate how the brain changes over time.

Data from Malmgren, R., in Textbook

of Geriatric Neuropsychiatry, 2000.

Brain changes

� Enlargement of the ventricular system: as people get older, the

volume of the ventricles (the spaces in the brain that contain cerebrospinal fluid) increases. It is thought that this enlargement occurs because cells surrounding the ventricles are lost.

� Widening of sulci (the grooves) on the surface of the brain.

� Reduced brain weight and brain volume: these changes are probably

caused by the loss of neurons. Reductions in the size of many areas of the cerebral cortex have been reported.

� Neurological disorders: brain disorders such as Alzheimer's disease,

Page 1 of 4Neuroscience Resources for Kids - Aging Brain

Parkinson's disease and stroke are more common in the elderly.

Changes in the Senses

Vision

� Lens: proteins in the lens change with age and the elasticity of the lens is

reduced. Therefore, many elderly individuals have trouble focusing their eyes. Exposure to ultraviolet light can also yellow the lens. Changes in the lens may affect color vision.

� Cornea: the cornea may become less transparent and more flat. This may

cause images to appear distorted or blurred. There may also be a loss of color sensitivity to green, blue and violet shades.

� Pupil: changes in the autonomic nervous system alter the ability of older people to dilate the

pupil. By age 70, the pupil may not dilate easily in low lighting conditions (Hampton, 1997).

� Cataracts: cloudy areas of the lens. Cataracts decrease the amount of light that passes through

the lens and can bend light abnormally. The National Eye Institute estimates that over 50% of Americans age 65 years and older have a cataract.

� Retina: the peripheral retina is thinner and contains fewer rods in older individuals.

� Other disorders of the eye common in the elderly: glaucoma, macular degeneration,

presbyopia.

Olfaction

� Changes in the nasal mucosa, cribriform plate and air passages may

contribute to impaired odor recognition.

� The amygdala and other brain areas involved with smell may be

damaged in older individuals.

Taste

Impairment in the ability to taste may be caused by:

� Medications that the elderly need.


� Reductions in the number of taste buds.

� Dentures that cover taste buds on the soft palate.

Audition

Hearing loss in the elderly may result from:

� Ear wax build up.

� Stiffening of the tympanic membrane (eardrum).

� Atrophy of small ear muscles.

� Degeneration of hair cells and support cells in the cochlea.

� Stiffening of basilar membrane.

� Loss of nerve fibers leading from the cochlea to the brain.

� Loss of neurons in auditory areas of the brain.

Touch

Age�related changes in the ability to perceive tactile stimuli may be due to:

� Loss of various receptors (for example, Meissner's and Pacinian

corpuscles) in the skin.

� Reductions in the number of sensory fibers innervating the skin.

For more information on the aging nervous system, see:

1. The American Psychiatric Press Textbook of Geriatric Neuropsychiatry, edited by C. E.

Coffey, J. L. Cummings, Washington, DC: American Psychiatric Press, 2000.

2. Hampton, J.K., Craven, R.F., and Heitkemper, M.M. The Biology of Human Aging, Dubuque:

Wm. C. Brown, 1997.


3. Hooper, C.R., Sensory and sensory integrative development, in Functional Performance in

Older Adults, edited by B.R. Bonder and M.B. Wagner, Philadelphia: F.A. Davis Company, 2001, pp. 121-136.

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Cranial Nerves

The cranial nerves are 12 pairs of nerves that can be seen on the ventral (bottom) surface of the brain. Some of these nerves bring information from the sense organs to the brain; other cranial nerves control muscles; other cranial nerves are connected to glands or internal organs such as the heart and lungs.

Cranial Nerves

Number Name Function Location

I Olfactory Nerve Smell

Page 1 of 6Neuroscience for Kids - Cranial Nerves

II Optic Nerve Vision

IIIOculomotor Nerve

Eye movement; pupil dilation

IV Trochlear Nerve Eye movement

V Trigeminal Nerve

Somatosensory information (touch, pain) from the face and head; muscles for chewing.

VI Abducens Nerve Eye movement


VII Facial Nerve

Taste (anterior 2/3 of tongue); somatosensory information from ear; controls muscles used in facial expression.

VIIIVestibulocochlear Nerve

Hearing; balance

IXGlossopharyngeal Nerve

Taste (posterior 1/3 of tongue); Somatosensory information from tongue, tonsil, pharynx; controls some muscles used in swallowing.

X Vagus Nerve

Sensory, motor and autonomic functions of viscera (glands, digestion, heart rate)

XISpinal Accessory Nerve

Controls muscles used in head movement.


XIIHypoglossal Nerve

Controls muscles of tongue

Note: the olfactory "nerve" is composed of the rootlets of olfactory hair cells in the nasal mucosa and is not visible on the ventral surface of the brain. The rootlets end in the olfactory bulb. The olfactory tract contains nerve fibers projecting out of the olfactory bulb to the brain. The images in this table have been adapted from those in the Slice of Life project.

Hear IT!

Olfactory Optic Oculomotor Trochlear

Trigeminal Abducens Facial Vestibulocochlear

Glossopharyngeal VagusSpinal Accessory

Hypoglossal

Can't remember the names of the cranial nerves? Here is a handy-dandy mnemonic for you:

On Old Olympus Towering Top A Famous Vocal German Viewed Some Hops.

The bold letters stand for:

olfactory, optic, oculomotor, trochlear, trigeminal, abducens, facial, vestibulocochlear, glossopharyngeal, vagus, spinal accessory, hypoglossal.

Still can't remember the cranial nerves? Perhaps you need some Cranial Nerve Bookmarks to help you study! After you print the bookmarks, cut them into three individual bookmarks and use them to mark your place when you study.

Test Your Cranial Nerves

Now that you know the names and functions of the cranial nerves, let's test them. These tests will help you understand how the cranial nerves work. These tests are not meant to be a "clinical examination" of the cranial nerves.

You will need to get a partner to help...both of you can serve as the experimenter (tester) and the


subject. Record your observations of what your partner does and says.

Olfactory Nerve (I) Gather some items with distinctive smells (for example, cloves, lemon, chocolate or coffee).

Have your partner smell the items one at a time with each nostril. Have your partner record what the item is and the strength of the odor. Now you be the one who smells the items...have your partner use different smells for you.

Optic Nerve (II) Make an eye chart (a "Snellen Chart") like the one on the right. It doesn't

have to be perfect. Have your partner try to read the lines at various distances away from the chart.

Oculomotor Nerve (III), Trochlear Nerve (IV) and Abducens Nerve (VI)

These three nerves control eye movement and pupil diameter. Hold up a finger in front of your partner. Tell your partner to hold his or her head still and to follow your finger, then move your finger up and down, right and left. Do your partner's eyes follow your fingers?

Check the pupillary response (oculomotor nerve): look at the diameter of your partner's eyes in dim light and also in bright light. Check for differences in the sizes of the right and left pupils.

Trigeminal Nerve (V) The trigeminal nerve has both sensory and motor functions. To test the motor part of the

nerve, tell your partner to close his or her jaws as if he or she was biting down on a piece of gum.

To test the sensory part of the trigeminal nerve, lightly touch various parts of your partner's face with piece of cotton or a blunt object. Be careful not to touch your partner's eyes. Although much of the mouth and teeth are innervated by the trigeminal nerve, don't put anything into your subject's mouth.

Facial Nerve (VII) The motor part of the facial nerve can be tested by asking your

partner to smile or frown or make funny faces. The sensory part of the facial nerve is responsible for taste on the front part of the tongue. You could try a few drops of sweet or salty water on this part of the tongue and see if your partner can taste it.

Vestibulocochlear Nerve (VIII) Although the vestibulocochlear nerve is responsible for hearing

and balance, we will only test the hearing portion of the nerve here. Have your partner close his or her eyes and determine the distance at which he or she can hear the ticking of a clock or stopwatch.


Glossopharyngeal Nerve (IX) and Vagus Nerve (X) Have your partner drink some water and observe the swallowing reflex. Also the

glossopharyngeal nerve is responsible for taste on the back part of the tongue. You could try a few drops of salty (or sugar) water on this part of the tongue and see if your partner can taste it.

Spinal Accessory Nerve (XI) To test the strength of the muscles used in head movement, put you hands on the sides of

your partner's head. Tell your partner to move his or her head from side to side. Apply only light pressure when the head is moved.

Hypoglossal Nerve (XII) Have your partner stick out his or her tongue and move it side to side.

Try it!

Do you like interactive word search puzzles? Make sure your browser is "java�enabled" and

try this one:

� Cranial Nerve Puzzle

� Cranial Nerve Information from Yale

University.

� Examination of the Cranial Nerves

� More details about the cranial nerves.

� A great cranial nerve review with quizes.

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The Blood-Brain-Barrier (BBB)

"Keep Out"

Over 100 years ago it was discovered that if blue dye was injected into the bloodstream of an animal, that tissues of the whole body EXCEPT the brain and spinal cord would turn blue. To explain this, scientists thought that a "Blood-Brain-Barrier" (BBB) which prevents materials from the blood from entering the brain existed. More recently, scientists have discovered much more about the structure and function of the BBB.

Anatomy of the BBB

The BBB is semi-permeable; that is, it allows some materials to cross, but prevents others from crossing. In most parts of the body, the smallest blood vessels, called capillaries, are lined with endothelial cells. Endothelial tissue has small spaces between each individual cell so substances can move readily between the inside and the outside of the vessel. However, in the brain, the endothelial cells fit tightly together and substances cannot pass out of the bloodstream. (Some molecules, such as glucose, are transported out of the blood by special methods.)

Although glial cells (astrocytes) form a layer around brain blood vessels, they do NOT contribute to the BBB. Rather, the astrocytes may be important for the transportation of ions from the brain to the blood.

Functions of the BBB

The BBB has several important functions:

1. Protects the brain from "foreign substances" in the blood that may injure the brain.

2. Protects the brain from hormones and neurotransmitters in the rest of the body.

3. Maintains a constant environment for the brain.

Page 1 of 3Neuroscience for Kids - Blood-Brain-Barrier

General Properties of the BBB

1. Large molecules do not pass

through the BBB easily.

2. Low lipid (fat) soluble molecules

do not penetrate into the brain. However, lipid soluble molecules, such as barbituate drugs, rapidly cross through into the brain.

3. Molecules that have a high

electrical charge to them are slowed.

The BBB can be broken down by:

1. Hypertension (high blood pressure): high blood

pressure opens the BBB

2. Development: the BBB is not fully formed at

birth.

3. Hyperosmolitity: a high concentration of a

substance in the blood can open the BBB.

4. Microwaves: exposure to microwaves can open

the BBB.

5. Radiation: exposure to radiation can open the

BBB.

6. Infection: exposure to infectious agents can open

the BBB.

7. Trauma, Ischemia, Inflammation, Pressure:

injury to the brain can open the BBB.

Circumventricular Organs

There are several areas of the brain where the BBB is weak. This allows substances to cross into the brain somewhat freely. These areas are known as "circumventricular organs".


Through the circumventricular organs the brain is able to monitor the makeup of the blood. The circumventricular organs include:

Pineal body Secretes melatonin and neuroactive peptides. Associated with circadian rhythms.

Neurohypophysis (posterior pituitary) Releases neurohormones like oxytocin and vasopressin into the blood.

Area postrema "Vomiting center": when a toxic substance enters the bloodstream it will get to the area postrema and may cause the animal to throw up. In this way, the animal protects itself by eliminating the toxic substance from its stomach before more harm can be done.

Subfornical organ Important for the regulation of body fluids.

Vascular organ of the lamina terminalis A chemosensory area that detects peptides and other molecules.

Median eminence Regulates anterior pituitary through release of neurohormones.

More information about the BBB and circumventricular organs from Loyola University School of Medicine and the Society for Neuroscience.

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The Skull

Your 3 pound (1.4 kg) brain needs a home...your skull!

Your brain is protected by several bones. There are eight bones that surround your brain: one frontal bone; two parietal bones, two temporal bones, one occipital bone, one sphenoid bone and one ethmoid bone. These eight bones make up the cranium.

Another 14 bones in the face make up the entire skull. There are also 3 small bones in each ear. Also protecting your brain are 3 layers of tissue called the meninges. A few of the bones have been colored in the diagram to the right.

There is a large opening, called the foramen magnum, located in the back of the occipital bone. This is where the medulla ends and projects out of the skull. Smaller holes in the skull, called foramina, allow nerves and blood vessels to enter and leave the cranium. The picture on the left shows the base of the skull.

The places in the skull where the bones come together are called sutures. These sutures are flexible in young children, but become fixed as you age.

Page 1 of 2Neuroscience for Kids - The Skull

DeLoy Roberts, a science teacher in Idaho Falls, has a nice collection of animal skulls that he has made available on the Internet.

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Page 2 of 2Neuroscience for Kids - The Skull

The Ventricular System and CSF

(Cerebrospinal Fluid)

The entire surface of central nervous system is bathed by a clear, colorless fluid called cerebrospinal fluid (CSF). The CSF is contained within a system of fluid-filled cavities called ventricles. The ventricles are shown in blue on the following midsagittal section of the brain.

The Ventricles

CSF is produced mainly by a structure called the choroid plexus in the lateral, third and fourth ventricles. CSF flows from the lateral ventricle to the third ventricle through the interventricular foramen (also called the foramen of Monro). The third ventricle and fourth ventricle are connected to each other by the cerebral aqueduct (also called the Aqueduct of Sylvius). CSF then flows into the subarachnoid space through the foramina of Luschka (there are two of these) and the foramen of Magendie (only one of these).

Absorption of the CSF into the blood stream takes place in the superior sagittal sinus through structures called arachnoid villi . When the CSF pressure is greater than the venous pressure, CSF will flow into the blood stream. However, the arachnoid villi act as "one way valves"...if the CSF pressure is less than the venous pressure, the arachnoid villi will NOT let blood pass into the

Page 1 of 3Neuroscience for Kids - Ventricles

ventricular system.

Ok..so there is CSF flowing through the ventricles...what does the CSF do? The CSF has several functions including:

1. Protection: the CSF protects the brain from

damage by "buffering" the brain. In other words, the CSF acts to cushion a blow to the head and lessen the impact.

2. Buoyancy: because the brain is immersed in

fluid, the net weight of the brain is reduced from about 1,400 gm to about 50 gm. Therefore, pressure at the base of the brain is reduced.

3. Excretion of waste products: the one-way

flow from the CSF to the blood takes potentially harmful metabolites, drugs and other substances away from the brain.

4. Endocrine medium for the brain: the CSF

serves to transport hormones to other areas of the brain. Hormones released into the CSF can be carried to remote sites of the brain where they may act.

Image adapted from Biodidac

Under some pathological conditions, CSF builds up within the ventricles. This condition is called hydrocephalus. Hydrocephalus may result from:

1. Overproduction of CSF

2. An obstruction at some point within the ventricular system

3. Problems with CSF absorption

To model how the CSF works, try out this experiment with Mr. Egghead!


Some CSF facts:

1. The total volume of CSF is 125�150 ml.

2. Normal resting pressure of the CSF is between 150�180 mm H2O.

3. Total production of CSF is about 400�500 ml/day (about .36 ml/min).

Hear It

"Ventricle""Choroid Plexus"

"Arachnoid villi"

"Hydrocephalus"

For more about CSF and hydrocephalus, see:

1. Formation, circulation and absorption of

CSF

2. The Hydrocephalus Foundation

3. National Hydrocephalus Foundation

4. The Hydrocephalus Association

5. Hydrocephalus � from Beth Israel Hospital

6. Hydrocephalus from Pediatric Neurosurgery

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Coverings (Meninges) of the Brain

There are several layers of tissue that separate your brain from the outside world. First, there is your skin (scalp). Beneath the skin is bone (your skull). Below the skull are three special coverings called the meninges. You may have heard of the illness called meningitis. Meningitis is an infection of the meninges.

The outer layer of the meninges is called the dura mater or just the dura. The dura is tough and thick and it can restrict the movement of the brain within the skull. This protects the brain from movements that may stretch and break brain blood vessels.

The middle layer of the meninges is called the arachnoid. The inner layer, the one closest to the brain, is called the pia mater or just the pia.

The Coverings of the Brain

Here is an easy way to remember the order of the meninges:

"The meninges PAD the brain."

Pia; Arachnoid; Dura.

Did you

The word "arachnoid" comes from the Greek words "arachne" and "�oid" which

mean "spider�like." The arachnoid was not discovered until 1664 by the Dutch

Page 1 of 2Neuroscience for Kids - Brain Coverings

know?

anatomist Gerardus Blasius.

The word "Arachne" which means "spider" comes from Greek mythology. According to the myth, a girl named Arachne was an excellent weaver. She challenged the Greek goddess Athena to a weaving contest. When Arachne wove a beautiful, perfect tapestry, Athena broke Arachne's loom and turned her into a spider.

See the Meningitis Research Foundation or the Meningitis Foundation of America for more

information about Meningitis. Perhaps your questions about the meninges will be answered here

at Top 20 Frequently Asked about Meningitis. Killer on Campus (from PBS) describes how meningitis affects young adults.

[Photographs of the Meninges]

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The Blood Supply of the Brain

Food and oxygen are carried to the brain by many blood vessels. These vessels are found on the surface of the brain and deep within the brain. The blood vessels (and nerves) enter the brain through holes in the skull called foramina (red arrows in the picture on the right).

Although the brain is only about 2% of the total body weight in humans, it receives 15-20% of the body's blood supply. Because brain cells will die if the supply of blood which carries oxygen is stopped, the brain has top priority for the blood. Even if other organs need blood, the body attempts to supply the brain with a constant flow of blood.

The blood brings many materials necessary for the brain to function properly. The blood also removes materials from the brain.

Blood is supplied to the entire brain by 2 pairs of arteries: the internal carotid arteries and vertebral arteries. As you can see in the figure below, the right and left vertebral arteries come together at the base of the brain to form a single basilar artery. The basilar artery joins the blood supply of the internal carotid arteries in a ring at the base of the brain. This ring of

Page 1 of 4Neuroscience for Kids - Blood Supply

arteries is called the circle of Willis. The circle of Willis provides a safety mechanism...if one of the arteries gets blocked, the "circle" will still provide the brain with blood.

Base of the brain

Only some of the vessels that exist in a real brain have been labeled.

Brain Attack = Stroke

You may know someone, a parent or grandparent, who has had a "stroke," also called a "brain attack." What exactly is a stroke? A stroke occurs when the blood supply to the brain is stopped. If this happens for enough time, neurons will start to die because they will not get enough oxygen. Paralysis or aphasia (loss of speech) are possible consequences of a stroke.

There are two major causes of a stroke:


� Blockage of a blood vessel (in the brain or neck) caused by:

� a blood clot in the brain or neck (this is called a thrombosis)

� a blood clot from somewhere else that has moved and now blocks a blood vessel in the

brain or neck (this is called an embolism)

� constriction or narrowing of an artery in the head or neck (this is called a stenosis)

� Bleeding of a blood vessel (this is called hemorrhagic stroke)

There are several warning signs that occur with a brain attack: Reprinted with permission from The National Institute of Neurological Disorders and Stroke

� Sudden weakness or numbness of the face, arm, or leg on one side of the body.

� Sudden dimness or loss of vision, particularly in one eye.

� Sudden difficulty speaking or trouble understanding speech.

� Sudden severe headache with no known cause.

� Unexplained dizziness, unsteadiness, or sudden falls, especially with any of the other signs.

There are several conditions linked to stroke: Reprinted with permission from The National Institute of Neurological Disorders and Stroke

� High blood pressure � Eat a balanced diet, maintain a healthy weight, and

exercise to reduce blood pressure. Drugs are also available.

� Cigarette smoking � Don't start smoking and if you do smoke, quit!

� Heart disease � Your doctor will treat your heart disease and may also

prescribe medication to help prevent the formation of clots.

� Diabetes � Treatment can delay complications that increase the risk of stroke.

� Transient ischemic attacks � These are brief episodes of stroke's warning signs and can be

treated with drugs or surgery.

Did you know?

� Each year there are 600,000 people in the United States who suffer a

stroke. Stroke is the THIRD leading cause of death in the US and kills about 160,000 Americans each year. (Statistic from American Stroke Association)

� The word "carotid" (carotid artery) comes from the Greek word karotis

meaning "deep sleep." This is because it has been known for a long time that pressure to the carotid arteries causes animals to become sleepy.


More about stroke:

� Chilled Brains � Hibernating animals may hold clues to novel stroke treatments

� Fighting back against Brain Attack

� Images of the brain after a stroke

� More facts about brain blood flow

� National Stroke Association

� StrokeCenter at Washington University School of Medicine

� Stanford Stroke Center

� Stroke � Quick Facts and Figures

� Stroke Relief

� In humans, the brain uses 15�20% of the body's oxygen supply. In the

African elephant nose fish, the brain uses 60% of the oxygen supply! (Source: Nilsson, G.E., Brain and body oxygen requirements of Gnathonemus perterssi, a

fish with an exceptionally large brain. J. Experi. Biol., 199:603�607, 1996.)

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Brain Facts and Figures

These data were obtained from several textbooks. Note that all data are estimates and averages. Check literature for appropriate references. All numbers are for humans unless otherwise indicated.

Brain

Table of Contents

BRAIN NEURON

SPINAL CORD

SENSORY APPARATUS

BLOOD SUPPLY

Average Brain Weights (in grams)

Species Weight (g) Species Weight (g)

adult human 1,300 - 1,400 newborn human 350 - 400

sperm whale 7,800 fin whale 6,930

elephant 6,000 humpback whale 4,675

gray whale 4,317 killer whale 5,620

bowhead whale 2,738 pilot whale 2,670

bottle-nosed dolphin 1,500 - 1,600 walrus 1,020 - 1,126

Pithecanthropus Man 850 - 1,000 camel 762

Page 1 of 15Brain Facts and Figures

giraffe 680 hippopotamus 582

leopard seal 542 horse 532

polar bear 498 gorilla 465 - 540

cow 425-458 chimpanzee 420

orangutan 370 California sea lion 363

manatee 360 tiger 263.5

lion 240 grizzly bear 234

sheep 140 baboon 137

adult rhesus monkey 90-97 dog (beagle) 72

aardvark 72 beaver 45

shark (great white) 34 shark (nurse) 32

cat 30 porcupine 25

squirrel monkey 22 marmot 17

rabbit 10-13 platypus 9

alligator 8.4 squirrel 7.6

opossum 6 flying lemur 6

fairy anteater 4.4 guinea pig 4

ring-necked pheasant 4.0 hedgehog 3.35

tree shrew 3 fairy armadillo 2.5

owl 2.2 grey partridge 1.9

rat (400 g body weight) 2 hamster 1.4

elephant shrew 1.3 house sparrow 1.0

european quail 0.9 turtle 0.3-0.7

bull frog 0.24 viper 0.1

goldfish 0.097 green lizard 0.08

Reference for many of these brain weights:

1. Blinkov, S.M. and Glezer, I.I. The Human Brain in Figures and Tables. A

Quantitative Handbook, New York: Plenum Press, 1968.

2. Demski, L.S. and Northcutt, R.G. The brain and cranial nerves of the white shark:

an evolutionary perspective. In Great White Sharks. The Biology of Carcharodon carcharias, San Diego: Academic Press, 1996.


% brain of total body weight (150 pound human) = 2%

Average brain width = 140 mm

Average brain length = 167 mm

Average brain height = 93 mm

Intracranial contents by volume (1,700 ml, 100%): brain = 1,400 ml (80%); blood = 150 ml (10%); cerebrospinal fluid = 150 ml (10%) (from Rengachary, S.S. and Ellenbogen, R.G., editors, Principles of Neurosurgery,

Edinburgh: Elsevier Mosby, 2005)

Average number of neurons in the brain = 100 billion Number of neurons in brain (octopus) = 300 million (from How Animals See, S. Sinclair, 1985)

Number of neurons in Aplysia nervous system = 18,000-20,000 Number of neurons in each segmental ganglia in the leech = 350

Volume of the brain of a locust = 6mm3 (from The Neurobiology of the Insect Brain, Burrows, M., 1996)

Ratio of the volume of grey matter to white matter in the cerebral hemipheres (20 yrs. old) = 1.3 (Miller,

A.K., Alston, R.L. and Corsellis, J.A., Variation with age in the volumes of grey and white matter in the cerebral hemispheres

of man: measurements with an image analyser, Neuropathol Appl Neurobiol., 6:119-132, 1980) Ratio of the volume of grey matter to white matter in the cerebral hemipheres (50 yrs. old) = 1.1 (Miller et al., 1980) Ratio of the volume of grey matter to white matter in the cerebral hemipheres (1000 yrs. old) = 1.5 (Miller et al., 1980) % of cerebral oxygen consumption by white matter = 6%

% of cerebral oxygen consumption by gray matter = 94%

Average number of glial cells in brain = 10-50 times the number of neurons

(For more information about the number of neurons in the brain, see R.W. Williams and K. Herrup, Ann. Review Neuroscience, 11:423-453, 1988)

Number of neocortical neurons (females) = 19.3 billion (Pakkenberg, B., Pelvig, D., Marner,L., Bundgaard, M.J.,

3. Nieuwenhuys, R., Ten Donkelaar, H.J. and Nicholson, C. The Central Nervous

System of Vertebrates. Vol. 3, Berlin: Springer, 1998.

4. Berta, A., et al. Marine Mammals. Evolutionary Biology, San Diego: Academic

Press, 1999.

5. Mink, J.W., Blumenschine, R.J. and Adams, D.B. Ratio of central nervous system

to body metabolism in vertebrates: its constancy and functional basis. Am. J. Physiology, 241:R203-R212, 1981.

6. Rehkamper, G., Frahm, H.D. and Zilles, K. Quantitative development of brain and

brain structures in birds (Galliformes and Passeriforms) compared to that in mammals (Insectivores and Primates). Brain Beh. Evol., 37:125-143, 1991.

7. Ridgway, S.H. and Harrison, S., Handbook of Marine Mammals, Vol. 3, London:

Academic Press, 1985.


Gundersen, H.J.G., Nyengaard, J.R. and Regeur, L. Aging and the human neocortex. Exp. Gerontology, 38:95-99, 2003 and Pakkenberg, B. and Gundersen, H.J.G. Neocortical neuron number in humans: effect of sex and age. J. Comp. Neurology, 384:312-320, 1997.)

Number of neocortical neurons (males) = 22.8 billion (Pakkenberg et al., 1997; 2003) Average loss of neocortical neurons = 85,000 per day (~31 million per year) (Pakkenberg et al., 1997; 2003) Average loss of neocortical neurons = 1 per second (Pakkenberg et al., 1997; 2003) Average number of neocortical glial cells (young adults ) = 39 billion (Pakkenberg et al., 1997; 2003) Average number of neocortical glial cells (older adults) =36 billion (Pakkenberg et al., 1997; 2003) Length of myelinated nerve fibers in brain = 150,000-180,000 km (Pakkenberg et al., 1997; 2003) Number of synapses in cortex = 0.15 quadrillion (Pakkenberg et al., 1997; 2003) Difference number of neurons in the right and left hemispheres = 186 million MORE neurons on left side than right side (Pakkenberg et al., 1997; 2003)

Total surface area of the cerebral cortex = 2,500 cm2 (2.5 ft

2; A. Peters, and E.G. Jones, Cerebral Cortex, 1984)

Proportion by Volume (%)

Rat Human

Cerebral Cortex 31 77

Diencephalon 7 4

Midbrain 6 4

Hindbrain 7 2

Cerebellum 10 10

Spinal Cord 35 2

(Reference: Trends in Neuroscience, November 1995)

Composition of Brain and Muscle

Skeletal Muscle (%) Whole Brain (%)

Water 75 77 to 78

Lipids 5 10 to 12

Protein 18 to 20 8

Carbohydrate 1 1

Soluble organic substances 3 to 5 2

Inorganic salts 1 1

(Reference: McIlwain, H. and Bachelard, H.S., Biochemistry and the Central Nervous System, Edinburgh: Churchill Livingstone, 1985)


Total surface area of the cerebral cortex (lesser shrew) = 0.8 cm2

Total surface area of the cerebral cortex (rat) = 6 cm2

Total surface area of the cerebral cortex (cat) = 83 cm2

Total surface area of the cerebral cortex (African elephant) = 6,300 cm2

Total surface area of the cerebral cortex (Bottlenosed dolphin) = 3,745 cm2 (S.H. Ridgway, The Cetacean

Central Nervous System, p. 221)

Total surface area of the cerebral cortex (pilot whale) = 5,800 cm2

Total surface area of the cerebral cortex (false killer whale) = 7,400 cm2

(Reference for surface area figures: Nieuwenhuys, R., Ten Donkelaar, H.J. and Nicholson, C., The Central nervous System of Vertebrates, Vol. 3, Berlin: Springer, 1998)

Total number of neurons in cerebral cortex = 10 billion (from G.M. Shepherd, The Synaptic Organization of the

Brain, 1998, p. 6). However, C. Koch lists the total number of neurons in the cerebral cortex at 20 billion (Biophysics of Computation. Information Processing in Single Neurons, New York: Oxford Univ. Press, 1999, page 87). Total number of synapses in cerebral cortex = 60 trillion (yes, trillion) (from G.M. Shepherd, The Synaptic Organization of the Brain, 1998, p. 6). However, C. Koch lists the total synapses in the cerebral cortex at 240 trillion (Biophysics of Computation. Information Processing in Single Neurons, New York: Oxford Univ. Press, 1999, page 87).

Percentage of total cerebral cortex volume (human): frontal lobe = 41%; temporal lobe = 22%; parietal lobe = 19%; occipital lobe = 18%. (Caviness Jr., et al. Cerebral Cortex, 8:372-384, 1998.)

Number of cortical layers = 6 Thickness of cerebral cortex = 1.5-4.5 mm

Thickness of cerebral cortex (Bottlenosed dolphin) = 1.3-1.8 mm (S.H. Ridgway, The Cetacean Central Nervous

System, p. 221)

EEG - beta wave frequency = 13 to 30 Hz EEG - alpha wave frequency = 8 to 13 Hz EEG - theta wave frequency = 4 to 7 Hz EEG - delta wave frequency = 0.5 to 4 Hz World record, time without sleep = 264 hours (11 days) by Randy Gardner in 1965. Note: In Biopsychology

(by J.P.J. Pinel, Boston: Allyn and Bacon, 2000, p. 322), the record for time awake is attributed to Mrs. Maureen Weston. She apparently spent 449 hours [18 days, 17 hours] awake in a rocking chair. The Guinness Book of World Records [1990] has the record belonging to Robert McDonald who spent 453 hours, 40 min in a rocking chair.

Time until unconsciousness after loss of blood supply to brain = 8-10 sec Time until reflex loss after loss of blood supply to brain = 40-110 sec

Rate of neuron growth (early pregnancy) = 250,000 neurons/minute Length of spiny terminals of a Purkinje cell = 40,700 micron Number spines on a Purkinje cell dendritic branchlet = 61,000

Surface area of cerebellar cortex = 50,000 cm2 (from G.M. Shepherd, The Synaptic Organization of the Brain, 1998,

p. 255)


Weight of adult cerebellum = 150 grams Afifi, A.K. and Bergman, R.A., Functional Neuroanatomy, New York:

McGraw�Hill, 1998

Number of Purkinje cells = 15�26 million

Number of synapses made on a Purkinje cell = up to 200,000 Weight of hypothalamus = 4 g

Volume of suprachiasmatic nucleus = 0.3 mm3

Number of fibers in pyramidal tract above decussation = 1,100,000 Number of fibers in corpus callosum = 250,000,000

Area of the corpus callosum (midsagittal section) = 6.2 cm2

Total volume of cerebrospinal fluid = 125�150 ml

Half life of cerebrospinal fluid = 3 hours Daily production of CSF = 400 to 500 ml Specific gravity of cerebrospinal fluid = 1.007 Color of normal CSF = clear and colorless

White Blood cell count in CSF = 0�3 per mm3

Red Blood cell count in CSF = 0�5 per mm3

Species Cerebellum Weight (grams)Body Weight (grams)

Mouse 0.09 58

Bat 0.09 30

Flying Fox 0.3 130

Pigeon 0.4 500

Guinea Pig 0.9 485

Squirrel 1.5 350

Chinchilla 1.7 500

Rabbit 1.9 1,800

Hare 2.3 3,000

Cat 5.3 3,500

Dog 6.0 3,500

Macaque 7.8 6,000

Sheep 21.5 25,000

Bovine 35.7 300,000

Human 142 60,000

Source: Sultan, F. and Braitenberg, V. Shapes and sizes of different mammalian cerebella. A study in quantitative comparative

neuroanatomy. J. Hirnforsch., 34:79�92, 1993.


Normal intracranial pressure = 150 � 180 mm of water

Number of cranial nerves = 12

I- olfactory

II- optic

Number of fibers in human optic nerve = 1,200,000 Number of fibers in cat optic nerve = 119,000 Number of fibers in albino rat optic nerve = 74,800 Length of optic nerve = 50 mm

III- oculomotor

Number of fibers in oculomotor nerve = 25,000-35,000

IV- trochlear

Number of fibers in trochlear nerve = 2,000-3,500 Number of neurons in nucleus of the trochlear nerve = 2,000-3,500

V- trigeminal

Number of fibers in motor root of trigeminal nerve = 8,100 Number of fibers in sensory root of trigeminal nerve = 140,000

Composition of Serum and Cerebrospinal Fluid (CSF)

CSF Serum

Water (%) 99 93

Protein (mg/dl) 35 7000

Glucose (mg/dl) 60 90

Osmolarity (mOsm/l) 295 295

Na (meq/l) 138 138

K (meq/l) 2.8 4.5

Ca (meq/l) 2.1 4.8

Mg (meq/l) 0.3 1.7

Cl (meq/l) 119 102

pH 7.33 7.41

(Reference: Fishman, R.A. Cerebrospinal Fluid in Disease of the Nervous System. Philadelphia: Saunders, 1980)


VI- abducens

Number of fibers in abducens nerve (at exit from brain stem) = 3,700

VII- facial

Number of fibers in facial nerve (at exit from brain stem) = 9,000-10,000 Length of nucleus of the facial nerve = 2 to 5.6 mm

Number of neurons in nucleus of the facial nerve = 7,000

VIII-vestibulocochlear IX- glossopharyngeal X- vagus

Length of dorsal motor nucleus of the vagus nerve = 10 mm

XI- spinal accessory XII- hypoglossal

Number of neurons in nucleus of the hypoglossal nerve = 4,500-7,500 Length of nucleus of the hypoglossal nerve = 10 mm

Spinal Cord

Number of neurons in human spinal cord = 1 billion (from Kalat, J.W., Biological Psychology, 6th Edition, 1998, page 24) Length of human spinal cord = 45 cm (male); 43 cm (female) Length of human vertebral column = 70 cm Length of cat spinal cord = 34 cm

Length of rabbit spinal cord = 18 cm

Weight of human spinal cord = 35 g Weight of rabbit spinal cord = 4 g Weight of rat spinal cord (400 g body weight) = 0.7 g Maximal Circumference of cervical enlargement = 38 mm

Maximal Circumference of lumbar enlargement = 35 mm

Pairs of Spinal Nerves = 31 Number of Spinal Cord segments = 31

8 cervical segments 12 thoracic segments

5 lumbar segments 5 sacral segments 1 coccygeal segment


Sensory Apparatus

Audition

Surface area of the tympanic membrane = 85mm2 (Hearing. Its

Physiology and Pathophysiology, A.R. Moller, San Diego, Academic Press, 2000)

Length of the eustachian tube = 3.5 to 3.9 cm (Hearing. Its Physiology and Pathophysiology, A.R. Moller, San Diego,

Academic Press, 2000.)

Number of hair cells in cochlea = 10,000 inner hair cells; 30,000 outer hair cells (Hearing. Its Physiology and Pathophysiology, A.R. Moller, San Diego, Academic Press, 2000. However, in the same book, Moller states that there are only 3,500 inner hair cells and 12,000 outer hair cells.)

Number of fibers in auditory nerve = 28,000-30,000 Length of auditory nerve = 2.5 cm

Number of neurons in cochlear nuclei = 8,800 (Northern, J.L. and Downs, M.P., Hearing in Children, 5th edition,

Philadelphia: Lippincott Williams & Wilkins, 2002.)

Number of neurons in inferior colliculus = 392,000 (Northern, J.L. and Downs, M.P., Hearing in Children, 5th

edition, Philadelphia: Lippincott Williams & Wilkins, 2002.)

Number of neurons in medial geniculate body = 570,000 Number of neurons in auditory cortex = 100,000,000 Hearing Range (young adult human) = 20 to 20,000 Hz Hearing Range (elderly human) = 50 to 8,000 Hz (Guyton, A.C., Textbook of Medical Physiology, 1986)

Hearing Range (rat) = 1,000 to 50,000 Hz Hearing Range (cat) = 100 to 60,000 Hz Hearing Range (dolphin) = 200 to 150,000 Hz Hearing Range (elephant) = 1 to 20,000 Hz Hearing Range (goldfish) = 5 to 2,000 Hz Hearing Range (moth, noctuid) = 1,000 to 240,000 Hz Hearing Range (mouse) = 1,000 to 100,000 Hz Hearing Range (sea lion) = 100 to 40,000 Hz (Hearing range reference: Discover Science Almanac, New York: Hyperion, 2003)

Most sensitive range of human hearing = 1,000-4,000 Hz Length of external auditory meatus (ear canal) = 2.7 cm

Diameter of external auditory meatus (ear canal)= 0.7 cm

Weight of malleus = 23 mg; length of malleus = 8-9 mm

Weight of incus = 30 mg; dimensions of incus = 5 mm by 7 mm

Weight of stapes = 3-4 mg; dimensions of stapes = 3.5 mm high, 3 mm long, 1.4 mm wide Malleus, incus and stapes references: Gelfand, S.A. Hearing: An Introduction to Psychological and Physiological Acoustics,

4th edition, New York: Marcel Dekker, 2004.

Length of cochlea = 35 mm

Width of cochlea = 10 mm

Number of turns in the cochlea = 2.2-2.9 Length of basilar membrane = 25-35 mm

Width of basilar membrane = 150 microns (at base of cochlea) (Hearing. Its Physiology and Pathophysiology,

A.R. Moller, San Diego, Academic Press, 2000.)

Auditory Pain Threshold = 130 db Threshold for hearing damage = 90 db for an extended period of time


Taste

Total number of human taste buds (tongue, palate, cheeks) = 10,000 Number of taste buds on the tongue = 9,000 Height of taste bud = 50-100 microns (From: Farbman, A.I., Taste Bud, in G. Adelman, eds., Encyclopedia of

Neuroscience, 1987) Diameter of taste bud = 30-60 microns (From: Farbman, A.I.)

Number of receptors on each taste bud = 50-150 (Boron, W.F. and Boulpaep, E.L., Medical Physiology. A Cellular and Molecular Approach, Philadelphia: Saunders, 2003)

Diameter of taste receptor = 10 micron Diameter of taste fiber = less than 4 micron Taste threshold for quinine sulfate = 3.376 mg/liter water

Smell

Number of human olfactory receptor cells = 12 million (Shier, D., Butler, J. and Lewis, R. Hole's Human Anatomy & Physiology, Boston: McGraw Hill, 2004)

Number of rabbit olfactory receptor cells = 100 million Number of dog olfactory receptor cells = 1 billion Number of bloodhound olfactory receptor cells = 4 billion (Shier, D., Butler, J. and Lewis, R. Hole's Human Anatomy & Physiology, Boston: McGraw Hill, 2004)

Surface area of olfactory epithelium (contains olfactory receptor cells) in humans = 10 cm2 (Bear, M.F.,

Connors, B.W. and Pradiso, M.A., Neuroscience: Exploring the Brain, 2nd edition, Baltimore: Lippincott Williams and

Decibel Sound Scale

Decibels Sound

180 Rocket launching pad

140 Jet plane

140 Gunshot blast

120 Automobile horn

130 Pain threshold

120 Discomfort

90 Subway

80 Noisy Restaurant

75 Busy traffic

66 Normal conversation

50 Average home

30 Soft whisper

Source: Lee, K.J., Essential Otolaryngology, 8th

edition, New York: McGraw-Hill,

2003.


Wilkins, 2001, p. 269)

Surface area of bloodhound olfactory epithelium = 59 in2 (Shier, D., Butler, J. and Lewis, R. Hole's Human

Anatomy & Physiology, Boston: McGraw Hill, 2004)

Area of olfactory epithelium in some dogs = 170 cm2 (Bear, M.F., Connors, B.W. and Pradiso, M.A.,

Neuroscience: Exploring the Brain, 2nd edition, Baltimore: Lippincott Williams and Wilkins, 2001, p. 269)

Area of olfactory epithelium in cats = 21 cm2 (Bradshaw, J., Behavioral biology, in The Waltham Book of Dog and

Cat Behaviour, ed. C. Thorne, Oxford: Pergamon Press, 1992)

Thickness of olfactory epithelium mucous layer = 20�50 microns. (Boron and Boulpaep, 2003)

Diameter of olfactory receptor axons = 0.1�0.2 micron

Diameter of distal end olfactory receptor cell = 1 micron

Diameter of olfactory receptor cell = 40�50 micron

Number of cilia per olfactory receptor cell = 10�30

Length of cilia on olfactory receptor cell = 100�150 micron

Concentration for detection threshold of musk = 0.00004 mg/liter air

Vision

Length of eyeball = 24.5 mm (from Spaide, R.F., 1999)

Volume of eyeball = 5.5 cm3

Weight of eyeball = 7.5 g Average time between blinks = 2.8 seconds

Average duration of a single blink = 0.1�0.4 seconds (Schiffman, H.R., Sensation and Perception. An Integrated

Approach, New York: John Wiley and Sons, Inc., 2001)

Thickness of cornea = 0.54 mm in center; 0.65 in periphery Diameter of cornea = 11.5 mm

Thickness of lens = 4 mm

Diameter of lens = 9 mm

Composition of lens = 65% water; 35% protein

Number of retinal receptor cells = 5�6 million cones; 120�140 million rods

Number of retinal ganglion cells = 800 thousand to 1 million Number of fibers in optic nerve = 1,200,000 Number of neurons in lateral geniculate body = 570,000 Number of cells in visual cortex (area 17) = 538,000,000

Wavelength of visible light (human) = 400�700 nm

Amount of light necessary to excite a rod = 1 photon Amount of light necessary to excite a cone = 100 photons

Location of the greatest density of rods = 20o from fovea

Highest density of rods = 160,000 per mm2

Peak density of rods (cat) = 400,000 per mm2


Density of cones in fovea = 200,000 per mm2

Diameter of fovea = 1.5 mm

Intraocular pressure = 10�20 mm Hg

Volume of orbit = 30 ml

Area of retina = 2,500 mm2

Thickness of retina = 120 microns (ranges from 100 to 230 microns) Production rate of aqueous humor = 2 microliters/min Turnover of aqueous humor = 15 times/day % volume of eye occupied by the vitreous = 80%

Maximal sensitivity of red cones = 570 nm

Maximal sensitivity of green cones = 540 nm

Maximal sensitivity of blue cones = 440 nm

More Facts and Figures about the Human Retina from WebVision.

Touch

Weight of skin (adult human) = 9 lb.(4.1 kg) (Source: Schiffman, H.R., Sensation and Perception. An Integrated Approach, New York: John Wiley and Sons, Inc., 2001)

Surface area of skin (adult human) = 3,000 in2 (~1.9 m

2) (Source: Schiffman, H.R., Sensation and Perception. An

Integrated Approach, New York: John Wiley and Sons, Inc., 2001)

Number of tactile receptors in the hand = 17,000

Number of nerve endings in hand = 1,300 per in2

von Frey threshold (Face) = 5 mg

2 point threshold (Finger) = 2�3 mm

Length of Meissner corpuscle = 90 � 120 micron

Density of receptors on finger tips = 2,500 per cm2

Density of Meissner's corpuscles on finger tips = 1,500 per cm2

Density of Merkel's cells on finger tips = 750 per cm2

Density of Pacinian corpuscles on finger tips = 75 per cm2

Density of Ruffini's corpuscles on finger tips = 75 per cm2

Thermal pain threshold = 45oC

Neurons

Mass of a large sensory neuron = 10�6

gram (from Groves and Rebec, Introduction

to Biological Psychology, 3rd edition, Dubuque: Wm.C. Brown Publ., 1988) Number of synapses for a "typical" neuron = 1,000 to 10,000 Diameter of neuron = 4 micron (granule cell) to 100 micron (motor neuron in


cord) Diameter of neuron nucleus = 3 to 18 micron Length of Giraffe primary afferent axon (from toe to neck) = 15 feet

Resting potential of squid giant axon = �70 mV

Conduction velocity of action potential = 0.6�120 m/s (1.2�250 miles/hr)

Single sodium pump maximum transport rate = 200 Na ions/sec; 130 K ions/sec

Typical number of sodium pumps = 1000 pumps/micron2 of membrane surface (from Willis and Grossman,

Medical Neurobiology, Mosby, St. Louis, 1981, p. 36)

Total number of sodium pumps for a small neuron = 1 million

Density of sodium channels (squid giant axon) = 300 per micron2 (from Hille, B., Ionic Channels of Excitable

Membranes, Sinauer, Sunderland, 1984, p. 210.)

Number of voltage�gated sodium channels at each node = 1,000 to 2,000 per micron2 (from Nolte, J., The

Human Brain, Mosby, 1999, p. 163.)

Number of voltage�gated sodium channels between nodes = 25 per micron2 (from Nolte, J., The Human Brain,

Mosby, 1999, p. 163.)

Number of voltage�gated sodium channels in unmyelinated axon = 100 to 200 per micron2 (from Nolte, J.,

The Human Brain, Mosby, 1999, p. 163.)

Diameter of microtubule = 20 nanometer Diameter of microfilament = 5 nanometer Diameter of neurofilament = 10 nanometer Thickness of neuronal membrane = 5 nanometer

Thickness of squid giant axon membrane = 50�100 A

Membrane surface area of a typical neuron = 250,000 um2 (Bear et al., 2001)

Membrane surface area of 100 billion neurons = 25,000 m2, the size of four soccer fields (Bear, M.F.,

Connors, B.W. and Pradiso, M.A., Neuroscience: Exploring the Brain, 2nd edition, Baltimore: Lippincott Williams and Wilkins, 2001, p. 97)

Typical synaptic cleft distance = 20�40 nanometers across (from Kandel et al., 2000, p. 176)

% neurons stained by Golgi method = 5%

Slow axoplasmic transport rate = 0.2-4 mm/day (actin, tubulin) Intermediate axoplasmic transport rate = 15-50 mm/day (mitochondrial protein) Fast axoplasmic transport rate = 200-400 mm/day (peptides, glyolipids) Number of molecules of neurotransmitter in one synaptic vesicle = 5,000 (from Kandel et al., 2000, p. 277)

Diameter of synaptic vesicle = 50 nanometer (small); 70-200 nanometer (large) Diameter of neurofilament = 7 - 10 nm

Diameter of microtubule = 25 nm

Internodal Length = 150 - 1500 microns (depends on fiber diameter % composition of myelin = 70-80% lipid; 20-30% protein

====================================


====================================

Neurotoxins

Blood Supply

% brain utilization of total resting oxygen = 20%

% blood flow from heart to brain = 15-20% (Kandel et al., 2000)

Blood flow through whole brain (adult) = 750 ml/min Blood flow through whole brain (adult) = 54 ml/100 g/min Blood flow through whole brain (child) = 105 ml/100 g/min

Cerebral blood flow = 55 to 60 ml/100 g brain tissue/min Cerebral blood flow (gray matter) = 75 ml/100 g brain tissue/min Cerebral blood flow (white matter) = 45 ml/100 g brain tissue/min (Rengachary, S.S. and Ellenbogen, R.G.,

editors, Principles of Neurosurgery, Edinburgh: Elsevier Mosby, 2005)

Oxygen consumption whole brain = 46 cm3/min

Oxygen consumption whole brain = 3.3 ml/100 g/min Blood flow rate through each internal carotid artery = 180 ml/min Blood flow rate through basilar artery = 380 ml/min Diameter of vertebral artery = 2-3 mm

Diameter of common carotid artery (adult) = 6 mm

Diameter of common carotid artery (newborn) = 2.5 mm

Ion Concentration (mM) - SQUID NEURON

Intracellular Extracellular

Potassium 400 20

Sodium 50 440

Chloride 40-150 560

Calcium 0.0001 10

Ion Concentration (mM) - MAMMALIAN NEURON

Intracellular Extracellular

Potassium 140 5

Sodium 5-15 145

Chloride 4-30 110

Calcium 0.0001 1-2

Data from Purves et al., Neuroscience, Sunderland: Sinauer Associates, 1997.


[Return to Neuroscience for Kids] | [Return to Eric H. Chudler's Home Page]


How the Nervous System Interacts with Other Body

Systems

All of the systems within the body interact with one another to keep an organism healthy. Although each system has specific functions, they are all interconnected and dependent on one another. The nervous system controls various organs of the body directly. The brain also receives information from many organs of the body and adjusts signals to these organs to maintain proper functioning.

SYSTEM FUNCTIONASSOCIATED

ORGANSINTERACTION WITH THE NERVOUS

SYSTEM

Skeletal System

The skeletal system makes up the framework of the body and allows us to move when our muscles contract. It stores minerals (e.g. calcium, phosphorous) and releases them into the body when they are needed. The skeletal system also protects internal organs and produces blood cells.

Bones (e.g., skull, vertebrae)

� Bones provide calcium that is

essential for the proper functioning of the nervous system.

� The skull protects the brain from

injury.

� The vertebrae protect the spinal

cord from injury.

� Sensory receptors in joints between

bones send signals about body position to the brain.

� The brain regulates the position of

bones by controlling muscles.

Cardiovascular The Heart, blood

Page 1 of 5Neuroscience Resources for Kids - Body System Interaction

System

cardiovascular system delivers oxygen, hormones, nutrients and white blood cells around the body by pumping blood, and it removes waste products.

vessels� Endothelial cells maintain the

blood-brain barrier.

� Baroreceptors send information to

the brain about blood pressure.

� Cerebrospinal fluid drains into the

venous blood supply.

� The brain regulates heart rate and

blood pressure.

Muscular System

Different types of muscles enable motion, generate heat to maintain body temperature, move food through digestive tract and contract the heart.

Muscles (smooth, skeletal and cardiac muscles)

� Receptors in muscles provide the

brain with information about body position and movement.

� The brain controls the contraction of

skeletal muscle.

� The nervous system regulates heart

rate and the speed at which food moves through the digestive tract.

Endocrine System

The endocrine system secretes hormones into blood and other body fluids. These chemicals are important for metabolism, growth, water and mineral balance, and the response to stress.

Pineal body, pituitary gland, hypothalamus, thyroid, parathyroid, heart, adrenal gland, kidney, pancreas, stomach, intestines, ovary

� Hormones provide feedback to the

brain to affect neural processing.

� Reproductive hormones affect the

development of the nervous system.

� The hypothalamus controls the

pituitary gland and other endocrine glands.


Lymphatic System

The lymphatic system protects the body from infection.

Adenoid, tonsils, thymus, lymph nodes, spleen

� The brain can stimulate defense

mechanisms against infection.

Respiratory System

The respiratory system supplies oxygen to the blood and removes carbon dioxide.

Lungs, larynx, pharynx, trachea, bronchi

� The brain monitors respiratory

volume and blood gas levels.

� The brain regulates respiratory rate.

Digestive System

The digestive system stores and digests foods, transfers nutrients to the body, eliminates waste and absorbs water.

Stomach, esophagus, salivary glands, liver, gallbladder, pancreas, intestines

� Digestive processes provide the

building blocks for some neurotransmitters.

� The autonomic nervous system

controls the tone of the digestive tract.

� The brain controls drinking and

feeding behavior.

� The brain controls muscles for

eating and elimination.

� The digestive system sends sensory

information to the brain.

Reproductive System

The reproductive system is responsible for producing new life.

Testes, vas deferens, prostate gland, ovary, fallopian tubes, uterus, cervix

� Reproductive hormones affect brain

development and sexual behavior.

� The brain controls mating behavior.


Urinary System

The urinary system eliminates waste products and maintains water balance and chemical balance.

Bladder, urethra, kidney

� The bladder sends sensory


� The brain controls urination.

Integumentary System

The integumentary system reduces water loss, contains receptors that respond to touch, regulates body temperature, and protects the inside of the body from damage.

Skin, hair� Receptors in skin send sensory


� The autonomic nervous system

regulates peripheral blood flow and sweat glands.

� Nerves control muscles connected

to hair follicles.

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There are a number of special words that are used to describe the position and direction of brain structures. These words help describe the location of structures relative to other structures. For example, we can say that the frontal lobe is "rostral" to the occipital lobe.

The brain, like all biological structures, is three dimensional. So, any point on or inside the brain can be localized on

three "axes" or "planes" � the x, y and

z axes or planes. The brain is often cut ("sectioned") into pieces for further study. These slices are usually made in one of three planes: the coronal plane, the horizontal plane or the sagittal plane.

The coronal plane, horizontal plane and sagittal plane are shown in the figure on the right. The coronal plane is also called the frontal plane. Slices

of the brain taken in the coronal plane are similar to the slices from a loaf of bread. Horizontal cuts are made as if you were slicing a hamburger bun or bagel.

The sagittal plane divides the right and left side of the brain into parts. The midsagittal plane would divide the right and left sides of the brain into two equal parts, like cutting down the middle of a baked potato before you put on the toppings.

Page 1 of 4Neuroscience for Kids - Directions/Planes

The figures below show the human brain in the three planes of section on "synthetic MR" images produced by BrainWeb:

You can find some photographs of coronal sections from the human brain at the Comparative Mammalian Brain Collection.

The LONI Resource is also available for viewing in coronal, horizontal and sagittal planes.

While visiting a new city or country, people often bring along a map. Neuroscientists who study the brain also use maps to identify exactly what part of the brain they are examining. These maps of the

Coronal Section

Sagittal Section

Horizontal Section


brain are called stereotaxic atlases. Just like maps, stereotaxic atlases use words to describe direction. However, instead of "north", "south", "east" and "west", the following words are used to describe direction in the brain (and other parts of the body too):

Directional Terms of the Body

Direction Description

Side View

Front View

Ventral Toward the belly (front)

Dorsal Toward the back

Rostral Toward the nose

Caudal Toward the tail

SuperiorToward the top of the head/body

Lateral Away from the middle

Medial Toward the middle

Bilateral On both sides

Ipsilateral On the same side

Contralateral On the opposite side

Try it!

Do you like interactive word search puzzles? Make sure your browser is "java�enabled" and

try this one:

� Directions and Planes of Section Puzzle

The Washington University School of Medicine also discusses planes of section and has some excellent human brain coronal section images.

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Brains, Brains, Brains

Can you guess which animal goes with each of these brains?

You can play three ways:

1. Click on the "answer button" below the picture after you have made a guess.

2. Click on a brain to see the animal the brain belongs to.

3. See all the answers at one time.

Here are your choices:

Chimpanzee Cat BeaverSquirrel Monkey

Spiny Anteater

Dolphin Manatee Capybara Least Weasel

Brain 1

Answer

Brain 2

Answer

Brain 3

Answer

Brain 4

Answer

Brain 5

Answer

Brain 6

Answer

Brain 7

Answer

Brain 8

Answer

Brain 9

Answer

Now that you have seen these brains, ask yourself the following questions.

1. What are the similarities and differences between the brains?

2. What are their relative sizes?

3. Identify areas of the brain. Cortex? Cerebellum?

Page 1 of 3Neuroscience for Kids - Brain Comparisons

4. Are their noticeable differences in any particular parts of the brains?

5. Is the cortex smooth or rough?

6. Compare the placement of the cerebellum and spinal cord.

7. Compare the size of the olfactory bulb.

8. Compare the size of the cerebral cortex.

9. Discuss brain weight vs body weight issues.

10. Discuss brain size and intelligence.

11. Discuss language and brain size.

12. Discuss cortical expansion in higher species.

(Images with the permission of Dr. Wally Welker of the Mammalian Brain Collection at the University of

Wisconsin)

The total surface area of the human cerebral cortex is about 2,500 cm2. This is about the

size of a pillow case (about 40 cm by 62.5 cm). How do the surface areas of the cortex from other animals compare? Below are the SURFACE AREAS of various brains. Your job is to calculate the dimensions (into a square or rectangle or circle) of these surface areas and to draw them on a piece of paper. After you see the size of each brain, you should think of a "common object" (such as a postage stamp or a piece of notebook paper) that fits the

dimensions. For example, if a surface area is 400 cm2, you can draw a square that is 20 cm by

20 cm (=400 cm2) and see its actual size (a little more than half a sheet of notebook paper).

Total surface area of the cerebral cortex (human) = 2,500 cm2

Total surface area of the cerebral cortex (lesser shrew) = 0.8 cm2

Total surface area of the cerebral cortex (rat) = 6 cm2

Total surface area of the cerebral cortex (cat) = 83 cm2

Total surface area of the cerebral cortex (African elephant) = 6,300 cm2

Total surface area of the cerebral cortex (Bottlenosed dolphin) = 3,745 cm2

Total surface area of the cerebral cortex (pilot whale) = 5,800 cm2

Total surface area of the cerebral cortex (false killer whale) = 7,400 cm2


(References for these surface area figures: Nieuwenhuys, R., Ten Donkelaar, H.J. and Nicholson, C., The Central Nervous System of Vertebrates, Vol. 3, Berlin: Springer, 1998; A. Peters, and E.G. Jones, Cerebral Cortex, 1984; S.H. Ridgway, The Cetacean Central Nervous System, p. 221)

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Invertebrates are those animals without a backbone (spinal column).

Invertebrates include animals such as insects, worms, jellyfish, spiders �

these are only a few of the many types of spineless creatures.

Invertebrates have played an important role in discoveries about how the nervous system works. The squid, aplysia (sea hare), leech, horseshoe crab, lobster, and cockroach have all provided scientists with models by which to study the nervous system. The squid even helped win the Nobel Prize in Physiology or Medicine in 1963.

Invertebrates are useful animals to study because their nervous system functions in basically the same way as that of vertebrates. Neurons in all animals work using an electrochemical process. Because the nervous system of invertebrates is less complex than that of vertebrates, it is easier to isolate and study neural functions in these animals without backbones.

Before reading about the nervous systems of some invertebrates, let's define a ganglion (plural is ganglia). A ganglion is a group or collection of nerve cell bodies.

Animal Nervous System Features/Behavior

Ameba/Paramecium

Although the ameba is a single�celled animal, it does

appear to be sensitive to the environment. This tiny animal moves away from light, but it has no

photodetectors or eyes. The paramecium, another single�

celled animal, also has no specialized sensory structures. However, it avoids cold, heat and chemicals by backing up and moving away.

Euglena (flagellate)

Euglena have an eyespot that acts as a shield for a light sensitive receptor. This small animal can detect the strength and direction of light. It prefers a location with moderate light and moves away from darkness and bright light. Euglena probably use this receptor to keep themselves in light which they use for photosynthesis. Euglena use photosynthesis for energy although they can eat solid food (like animals) if they are kept in the

Page 1 of 7Neuroscience for Kids - Invertebrate Nervous System

Image courtesy of Biodidac darkness.

Sponge

Image courtesy of Biodidac

Sponges are the only multicellular animals without a nervous system. They do not have any nerve cells or sensory cells. However, touch or pressure to the outside of a sponge will cause a local contraction of its body.

Hydra

The hydra has a nervous system characterized by a nerve net. A nerve net is a collection of separate, but "connected" neurons. Neurons are connected by synapse. Communication between neurons can be in both directions at the synapse within a nerve net. The nerve net is concentrated around the mouth. Unlike higher animals, the hydra does not have any grouping of nerve cell bodies. In other words, there are no ganglia.

The hydra does have specialized cells for touch and chemical detection.

Jellyfish

Like the hydra, the jellyfish has a nervous system characterized by a series of interconnected nerve cells (a nerve net). The nerve net conducts impulses around the entire body of the jellyfish. The strength of a behavioral response is proportional to the stimulus strength. In other words, the stronger the stimulus, the larger the response.

Some jellyfish (for example, Aurelia) have specialized structures called "rhopalia". These rhopalia have receptors for:

� light (called ocelli)

� balance (called statocysts)

� chemical detection (olfaction),

� touch (called sensory lappets)

Shown to the left


is a statocyst. When the animal moves and body is tilted, the statocyst makes contact with the cilium. When the cilium bends, it causes action potentials to fire in a nerve. This provides information to move muscles.

Anemone

Like the jellyfish and hydra, the anemone has a nerve net.

Flatworms (Planaria)

The nervous system of the flatworm has an organization different from the invertebrates describe above. It does have a nerve net, but these are connected by long nerve cords. These cords are connected to cerebral ganglia located in the head region. The central nervous system has been described as "ladder-like" because of the nerves connecting the nerve cords.

Flatworms have "auricles" that project from the side of the head. These auricles contain chemoreceptors that are used to find food. Flatworms also have eyespots called "ocelli". The ocelli are sensitive to light and are connected to the cerebral ganglia. Generally, the flatworm avoids light.

Earthworm

The nervous system of the earthworm is "segmented" just like the rest of the body. The "brain" is located above the pharynx and is connected to the first ventral ganglion. The brain is important for movement: if the brain of the earthworm is removed, the earthworm will move continuously. If the first ventral ganglion is removed, the earthworm will stop eating and will not dig. Each segmented ganglion gets sensory information from only a local region of its body and controls muscles only in this local region.


Earthworms have touch, light, vibration and chemical receptors all along the entire body surface.

Sea Star ("Starfish")

The nervous system of the starfish is very simple...there is no brain and there are not even any ganglia to coordinate movement. The nervous system is characterized by a nerve ring that surrounds the mouth. A radial nerve branches off of the nerve ring and extends to each arm. The picture on the left shows one of 3 nerve nets that extend throughout the body.

Starfish have an interesting way of detecting light. They have "eyespots" at the tip of each arm. The eyespot contains light sensitive pigments that allow the starfish to detect shadows and changes in the brightness of light.

Snails

The nervous system is characterized by 6 ganglia. Some snails have chemosensors called "osphradia" in the mantle cavity. These osphradia are used to detect chemicals in the air or water.

Aplysia (Sea Hare)

Image courtesy of BrainSurf

The aplysia has several ganglia that are connected by long nerves. The cell bodies of some neurons are very large (1 mm in diameter). Neuroscientists like these cells because they are easy to: 1) see 2) record action potentials 3) inject chemicals.

Bivalves (clams, scallops)

The nervous system is comprised of 3 pairs of ganglia (cerebral, visceral and pedal) each associated with the esophagus, muscles close to the shell, and foot.


Crab

The crab has a condensed central nervous system consisting of several ganglia.

Lobster

The lobster has a brain connected to a first ventral ganglion. This ganglion is located under its stomach. A double nerve cord extends from the first ventral ganglion to a series of paired segmental ganglia running through the entire body on the ventral side of the animal.

Insects (such as grasshoppers)

The grasshopper has a brain located between its eyes, just above the esophagus. The brain is connected to the 1st ventral ganglion by a pair of ventral nerves that surround the gut. The grasshopper can do many things, like walking and jumping, WITHOUT its brain. The brain is used to relay sensory information to other parts of the body and to help with movement. The first ventral ganglion is used primarily to control movement of the mouth. The segmental ganglia throughout the length of the grasshopper are connected to the first ventral ganglion by a double nerve cord and serve to coordinate local activities.

Insects have a compound eye containing many different units called "ommatidia". Each ommatidia is like an individual lens that samples a small part of the visual field. There can be thousands of ommatidia in a single insect eye. Science fiction/horror/monster movies that show an insect that sees thousands of identical images of the ENTIRE visual field are WRONG -- an insect sees


only ONE picture at a time because each ommatidia sees only a small part of the entire field. Some insects are sensitive to ultraviolet light and others can detect infrared wavelengths of light.

Octopus

The octopus has the most complicated brain of all the invertebrates. The octopus brain is estimated to have 300,000,000 neurons. These neurons are arranged in lobes and tracts that are more specialized than simple ganglia. An octopus has a "good" memory and can also learn.

The eye of the octopus is very similar to that of vertebrates in that it has a cornea, lens, iris and retina. It can also focus and form images. However, the octopus eye is different from that of vertebrates in that it focuses light by moving the lens closer and further away from the retina. The vertebrate eye focuses by changing the shape of the lens. Octopi can perceive shape, color intensity and texture. Another difference is that the eye of the octopus has NO blind spot because the nerve cells leave from the outside of the eyeball. The octopus also has a statocyst located next to the brain. The statocyst is used to detect changes in gravity and respond to acceleration.

Try this experiment using an earthworm.

Did you know?

� The world's largest invertebrate is the GIANT SQUID � (Architeuthis dux).

The giant squid can grow up to 18 m (59 ft) long and weigh up to 900 kg (1,980 lb).

� Approximately 99% of the world's animals are invertebrates. (Turin, M.S.

Aardvarks to Zebras, New York: Citadel Press, 1995)


For more information on invertebrates, see:

1. Amazing Animal Senses

2. B�Eye � the eye of the honey bee

3. Insect Anatomy

4. Insect Nervous Systems

5. Insects

6. Jellyfish

7. Using Insects in the Classroom

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What is Sleep... and why do we do it?

We spend about 8 hours/day, 56 hours/week, 224 hours/month and 2,688 hours/year doing it...that's right...SLEEPING. We apparently spend one third of our lives doing nothing. But is sleep really doing nothing? It looks like it...our eyes are closed, our muscles are relaxed, our breathing is regular, and we do not respond to sound or light. If you take a look at what is happening inside of

your brain, however, you will find quite a different situation � the brain is very active. You are doing

something!

Scientists can record brain activity by attaching electrodes to the scalp and then connecting these electrodes to a machine called an electroencephalograph. The encephalogram (or EEG) is the record of brain activity recorded with this machine. The wavy lines of the EEG are what most people know as "brain waves."

Stages of Sleep

Sleep follows a regular cycle each night. The EEG pattern changes in a predictable way several times during a single period of sleep. There are two basic forms of sleep: slow wave sleep (SWS) and rapid eye movement (REM) sleep. (REM sleep is sometimes

called "paradoxical sleep.") Infants spend about 50% of their sleep time in SWS and 50% in REM sleep. Adults spend about 20% of their sleep time in REM and 80% in SWS sleep. Elderly people spend less than 15% of their sleep time in REM sleep.

These lines represent the EEG (electroencephalogram) which shows a record of brain activity; the EMG (electromyogram) shows muscle activity; the EOG (electroculogram) shows eye movements. Look at the

differences in the EEG, EMG and EOG during waking, REM sleep (Rapid Eye Movement Sleep) and SWS sleep.

Page 1 of 7Neuroscience for Kids - Sleep

REM Sleep

Color in Dreams?

Do you dream in color?

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Most dreaming occurs during REM sleep. During REM sleep, a person's eyes move back and forth rapidly. Sleep researchers discovered this when they woke people up during REM sleep. Often when people in REM sleep wake up, they say that they were just dreaming. The EEG pattern during REM sleep is similar to the EEG pattern when people are awake. However, the muscle activity is very quiet during REM sleep. Muscles are inactive to prevent us from acting out our dreams. This also means that sleepwalkers are not in REM sleep and are not acting out their dreams.

SWS sleep is actually 4 different stages of sleep (Stage 1, Stage 2, Stage 3 and Stage 4) with different EEG patterns.

StageEEG Rate

(Frequency)EEG Size

(Amplitude)

Awake 8�25 Hz Low

1 6�8 Hz Low

2

4�7 Hz

Occasional "sleep spindles"

Occasional "K" complexes

Medium

3 1�3 Hz High

4 Less than 2 Hz High

REM More than 10 Hz Low

While we are asleep, our brains are on a bit of a "roller-coaster" through different stages of sleep. As we drift off to sleep, we first enter stage 1 sleep. After a few minutes, the EEG changes to stage 2 sleep, then stage 3 sleep, then stage 4 sleep. Then it's back up again: stage 3, stage 2, then a period of REM sleep...then it's back down again, and back up again, and down again...you get the picture. As shown in the figure below, in an 8 hour period of sleep, the brain cycles through these stages about 4-5 times.


Age-related changes in total amount of sleep and REM Sleep

Data from Roffwarg et al., Ontogenetic development of the human sleep-dream cycle, Science, 152:604-619, 1966

Sleep patterns change as people age. As shown in the two graphs above, infants spend more time sleeping and spend a greater percentage of sleep in REM sleep compared with the times of older children and adults. For example, newborn babies sleep about 16 hours per day and spend about 50% of that time in REM sleep. Older people (50-85 years old) sleep only 5.75-6 hours per day and spend 13.8-15% of that time in REM sleep.

As you might expect, as children grow, they spend less time sleeping during the day. The graph below illustrates how nighttime and daytime sleep time changes with age.


Data from Howard, B.J. and Wong, J. Sleep disorders, Pediatrics in Review, 22:327-341, 2001.

Did you

know?

Did you ever think about how much you sleep and dream? The "average" human sleeps about

8 hours every day. That's one third of

your life! In other words, you sleep for about 122 days every year. A 75 year old person would have spent a total of about 25 years asleep. There is a wide range in the amount of time different animals spend sleeping.

As for dreaming...we enter REM sleep about 5 times in an average 8 hour period of sleep. If we assume that we dream during each of these REM periods, then in one year, we will have had 1,825 dreams! Of course we don't remember all of these dreams. A 75 year old person would have about 136,875 dreams!

Sleep Poll

About how many hours of sleep do you get each night?

3-5 hours

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Why Sleep?

Why sleep at all? It seems like a big waste of time. Think of all you could be doing if you did not sleep. Nevertheless, sleep appears to be necessary. There is a continuing debate about why we sleep. Why do most animals sleep? How much sleep is required?

Most "higher" animals appear to sleep during some portion of the day and/or night. � they are quiet; they

rest; they do not move. Scientists have recorded sleep�like EEG patterns in birds, reptiles and mammals, but

it is not clear if insects and other invertebrates also sleep.

No one knows for sure why we sleep, but here are 2 basic theories:


1. Sleep has a restorative function.

2. Sleep has an adaptive function.

Sleep as a Restorative Process

This theory of sleep suggests that sleep helps the body recover from all the work it did while an animal was awake. Experiments have shown that the more physical exercise an animal does, the more SWS an animal will have. Also, if people are deprived of SWS by waking them up each time they get to stage 4 sleep, then they complain of being physically tired. If people are deprived of REM sleep by waking them up each time the have REM type EEG patterns, they can get anxious and irritable. If animals are deprived of REM for several days and then allowed to get an

undisturbed period of sleep, animals will go into "REM rebound" � this is when REM periods of

sleep will happen more often and for a longer time than normal.

Sleep, especially REM sleep, has also been thought to be important for memory and learning. It is possible that sleep helps form memories.

Sleep as an Adaptive Process

Sleep may have developed because of a need of animals to protect themselves. For example, some animals search for food and water during the day because it is easier to see when the sun is out. When it is dark, it is best for these animals to save energy, avoid getting eaten, and avoid falling off a cliff that they cannot see. It is interesting to note which animals sleep the most and which sleep the least. In general, animals that serve as food for other animals sleep the least.

Highlights from the National Sleep Foundation's 2001 Sleep in America telephone survey of 1,004 adults:

� 63% of the surveyed adults get less than the recommended eight hours of sleep per night;

31% get less than seven hours.

� 40% of surveyed adults in the US report having trouble staying awake during the day.

� Over the last five years, people in the US have worked more and slept less.

� Eight out of ten people said that they would sleep more if they knew it would improve their

health and memory.

Did you know?

� Sleep disorders affect up to 70 million people in the United States. This costs about $100

billion each year in accidents, medical bills and lost work. (Statistic from Brain Facts, Society for

Neuroscience, 2002)

� Sleepwalking is also known as "somnambulism"; sleeptalking is also known as

"somniloquy."


Try these sleep experiments on your own.

Do you like interactive word search puzzles? Make sure your browser is "java�enabled" and try

this one:

� Sleep Puzzle

For more information on sleep, see:

1. National Center on Sleep Disorders Research

2. TalkAboutSleep.com

3. Brain Basics � Understanding Sleep

4. National Sleep Foundation

5. Sleep and Learning � Society for Neuroscience

6. Tossing and Turning No More: How to Get a Good Night's

Sleep

7. The Phenomena of Human Sleep

They said it!

"Early to bed, and early to rise, makes a man healthy, wealthy, and wise."

�� Benjamin Franklin, 1758 (in Poor Richard's Almanack)

"The woods are lovely, dark and deep. But I have promises to keep, and miles to go before I sleep."

�� Robert Frost, 1923 (in Stopping By Woods On A Snowy

Evening)

"Sleep is better than medicine."

�� English Proverb

"The beginning of health is sleep."

�� Irish Proverb

"In sleep we are all equal."

�� Spanish Proverb

"Disease and sleep keep far apart."


�� Welsh Proverb

"Dreaming of eating will not satisfy the hungry."

�� African Proverb

"Sleep is an acquired habit. Cells don't sleep. Fish swim in the water all night. Even a horse doesn't sleep. A man doesn't need any sleep."

�� Thomas Edison, inventor

"I never use an alarm clock. I can hardly wait until five a.m. In the army I always woke before reveille. I hate sleeping. It wastes time."

�� Isaac Asimov, science fiction writer

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Kids


Most animals have a daily pattern of rest and activity. Some animals are more active during the day (diurnal) and some are more active during the night (nocturnal). How much time do animals spend sleeping? Well, it depends on the animal:

How Much Do Animals Sleep?

SpeciesAverage Total Sleep

Time (% of 24 hr)

Average Total Sleep Time

(Hours/day)

Brown Bat 82.9% 19.9 hr

Giant Armadillo 75.4% 18.1 hr

North American Opossum

75% 18 hr

Python 75% 18 hr

Owl Monkey 70.8% 17.0 hr

Human (infant) 66.7% 16 hr

Tiger 65.8% 15.8 hr

Tree shrew 65.8% 15.8 hr

Squirrel 62% 14.9 hr

Western Toad 60.8% 14.6 hr

Ferret 60.4% 14.5 hr

Three-toed Sloth 60% 14.4 hr

Golden Hamster 59.6% 14.3 hr

Platypus 58.3% 14.0 hr

Lion 56.3% 13.5 hr

Gerbil 54.4% 13.1 hr

Rat 52.4% 12.6 hr

Cat 50.6% 12.1 hr

Cheetah 50.6% 12.1 hr

Mouse 50.3% 12.1 hr

Rhesus Monkey 49.2% 11.8 hr

Rabbit 47.5% 11.4 hr

Jaguar 45% 10.8 hr

Duck 45% 10.8 hr

Dog 44.3% 10.6 hr

Page 1 of 3Neuroscience for Kids - Animal Sleep

References: This table was adapted from four sources:

1. Aserinsky, E., Eyelid condition at birth: relationship to adult mammalian sleep-waking patterns, In Rapid Eye

Movement Sleep, edited by B.N. Mallick and S. Inoue, Narosa Publishing, New Delhi, 1999, p. 7.

2. Campbell, S.S. and Tobler, I., Animal sleep: a review of sleep duration across phylogeny. Neuroscience and

Biobehavioral Rev., 8:269-300, 1984.

3. Kryger, M.H., Roth, T. and Dement, W.C., Principles and Practice of Sleep Medicine, W.B. Saunders Co.,

Philadelphia, 1989, pp. 39-41.

4. Tobler, I., Napping and polyphasic sleep in mammals, In Sleep and Alertness: Chronobiological, Behavioral and

Medical Aspects of Napping, edited by D.F. Dinges and R.J. Broughton, Raven Press, New York, 1989, pp. 9-31.

Bottle-nosed dolphin 43.3% 10.4 hr

Star-nosed Mole 42.9% 10.3 hr

Baboon 42.9% 10.3 hr

European Hedgehog 42.2% 10.1 hr

Squirrel Monkey 41.3% 9.9 hr

Chimpanzee 40.4% 9.7 hr

Guinea Pig 39.2% 9.4 hr

Human (adult) 33.3% 8 hr

Pig 32.6% 7.8 hr

Guppy (fish) 29.1% 7 hr

Gray Seal 25.8% 6.2 hr

Human (elderly) 22.9% 5.5 hr

Goat 22.1% 5.3 hr

Cow 16.4% 3.9 hr

Asiatic Elephant 16.4% 3.9 hr

Sheep 16% 3.8 hr

African Elephant 13.8% 3.3 hr

Donkey 13.0% 3.1 hr

Horse 12.0% 2.9 hr

Giraffe 7.9% 1.9 hr

Did you know? The brain of a dolphin appears to sleep one hemisphere at a


time.

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Brain Fitness � Your Guide to Good Brain

Health

You are born with just about all the neurons (nerve cells) that your

brain will ever have*. Damaged brains are NOT easy to fix. Here are

some suggestions for good brain health.

1. Wear your seat belt!

In a car, truck or airplane, your seat belt will help protect your head and brain from injury. Motor vehicle accidents are by far

the greatest causes of brain injuries, accounting for 37�50% of

all brain injuries.

(Statistic from Amer. J. of Diseases of Children, Vol. 144,

pages 627�646, 1990 and Brain Injury Association USA)

Seat Belts

When riding in or driving a car, how often do you wear

a seat belt?

Always

Sometimes

Never

Vote

Current results

Free Web Polls

Helmets

When riding a bike, how

often do you wear a helmet?

Always

Sometimes

Never

Vote

Current results

Free Web Polls

2. Wear your helmet!

Whether you are biking, skating or skateboarding, your helmet will protect your head if you fall. Make sure that your helmet meets or exceeds the American National Standards Institute (ANSI) and Snell Memorial Foundation standards for safety.

Head injury is the most common cause of death in bicycle crashes

accounting for 62% of all bicycle�related deaths. (Statistic from

Morbidity and Mortality Weekly Report, Vol. 44, No. RR�1, pages 1�17,

1995)

More information on bicycle injury.

Page 1 of 4Neuroscience for Kids - Brain Fitness

3. Stay away from illegal drugs!

Drugs alter brain function � no question about that. Although damage done by some

drugs can be reversed, some drugs may change brain function permanently. Why take the chance?

4. Know the risks involved with sports!

This applies mainly to boxing, football and the martial arts. However, even soccer, climbing, horseback riding, diving and skiing have risks. Always wear your safety equipment properly and be in good physical condition for your sport.

In the United States in 1987 and 1988, 92,763 emergency room visits were made for injuries related to horseback riding. 18.9% of these visits were made due to injuries to the head and neck. (Statistic from Morbidity and Mortality Weekly Report, Vol. 39, no.

20, pages 329�332, 1990)

Did you know?

Each year there are about 300,000 brain concussions that occur during sports activities. This statistic from the Center for Disease Control.

5. Look before you leap!

I know it sounds impossible, but people DO dive into swimming pools without water. Dive only in the deep end of the pool and make sure that the water in the lake and at the beach is deep enough to dive in head first. Also, be aware of any objects, such as large rocks, that may be hidden under the water.

There are up to 1,000 spinal cord injuries each year in the United States when people

dive into swimming pools or other bodies of water � (Statistic from Morbidity and

Mortality Weekly Report, Vol. 37, no. 30, pages 453�454, 1988)

6. Look both ways before crossing the street!

I know that you have heard this one before, but accidents do happen and you can't be wearing your helmet all the time.

7. Stay away from guns!


I don't think I have to explain this one.

8. Make sure you have a "good" surface around your playground equipment!

Just in case you fall off of a climber, a soft impact�absorbing surface will cushion your

drop.

In the United States from 1983�1987, 66.5% of the school playground�related injuries

involved the head and neck.(Statistic from Morbidity and Mortality Weekly Report,

Vol. 37, no. 41, pages 629�632, 1988)

National Program for Playground Safety

9. Eat right!

Your brain needs energy to work its best.

10. Dispose of chemicals properly!

Many chemicals, such as pesticides and cleaners, contain neurotoxins that can kill nerve cells and damage nerves. These dangerous chemicals can be found in your home or at places of work. Dispose of these materials properly!

Did you know?

Each year in the United States, there are about 52,000 deaths caused by traumatic brain injury. This statistic from the Center for Disease Control.

*Note: Other data suggest that new neurons DO grow in the brain after birth. This has been

demonstrated in rats, tree shrews, marmosets, monkeys and humans.

For more about brain injury and protecting your head, see:


1. Anatomy of Head Injury

2. Bicycle Helmet Effectiveness (large file � 150k)

3. Bicycle Helmet Safety Institute

4. Brain Injury Association of Kansas and Greater Kansas City � basic information about

prevention of brain injury

5. Brain Injury � A Guide for Families and Friends

6. Brain Injury: Prevention

7. Consumer's Guide to Bicycle Helmets

8. Injury�Control Recommendations: Bicycle Helmets

9. Preventing Mental Retardation Through Use of Bicycle Helmets

10. Help in Planning a Helmet Promotion Program

11. Think First Oregon

12. TBI Help Desk

13. Traumatic Brain Injury at the Centre for Neuro Skills

14. Understanding Brain Injury

For information on spinal cord injury, see the the Spinal Cord Injury Home Page and the home page of Cure Paralysis Now. The National Spinal Cord Injury Association also has lots of good information about spinal cord damage.

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Neurological Disorder Resources

Alzheimer's Disease

� Alzheimer Association

� Alzheimer's Disease � Doctor's Guide

� Alzheimer's Disease � Science�Week Focus Report

Aphasia

� Aphasia Fact Sheet

Bell's Palsy

� Facial Nerve Paralysis

� Bell's Palsy � I

� Bell's Palsy � II

Creutzfeldt�Jakob Disease (CJD)

� Blood Recall/Withdrawal � CJD

� BSE �� Bovine Spongiform Encephalopathy ("Mad Cow Disease")

� CJD information from the National Center for Infectious Diseases

Alzheimer's Disease

Aphasia Bell's PalsyCreutzfeldt�Jakob

Disease

Epilepsy EncephalitisHuntington's Disease

Neuromuscular Disorders

Neuro�oncology Neuro�

immunology Neuro�otology Pain

Pediatric Neurology Phobia List Sleep Disorders Tourette Syndrome

Parkinson's Disease and other movement disorders

Page 1 of 5Neurological Disorders

� CJD Voice

� Creutzfeldt�Jakob Disease Foundation, Inc.

� Official Mad Cow Disease Home Page

Cerebrovascular Disease

� Aneurysm Information Project

� National Stroke Association

� NINDS Stroke Information Guide

Encephalitis

� Encephalitis � eMedicine

� Encephalitis (Arbovirus) � CDC

� Encephalitis � Mayo Clinic

� Encephalitis (Nemours Foundation)

� Encephalitis Information Resource

Epilepsy

� Epilepsy � from Neuroscience for Kids

� EpiCentre

� Epilepsy � World Health Organization (WHO)

� Epilepsy Treatment � WHO

� Epilepsy History� WHO

� Epilepsy � Social/Economic � WHO

� Epilepsy Fact Sheet� from NINDS, NIH

� Epilepsy Foundation of America

� Frequently Asked Questions about Epilepsy

� Epilepsy � Genes may build the road in treatment

Huntington's Disease

� Index � Internet Resources for Huntington's Disease


� Huntington's Disease Resources

� Huntington's Disease Society of America

Pain

� American Council for Headache Education

� Talaria� Cancer Pain Information (Univ. Washington)

� Migraine � Doctor's Guide to the Internet

� Migraine Resource Center

� Trigeminal Neuralgia Association Homepage

� Trigeminal Neuralgia � from the International Radiosurgery Association

Phobia List

Parkinson's Disease and other movement disorders

� American Parkinson Disease Association

� Michael J. Fox Foundation

� Dystonias � National Institutes of Health

� National Parkinson Foundation

� Parkinson's Disease� Hope Through Research (NINDS, NIH)

� Parkinson's Disease Foundation

� Parkinson's Disease Index

� Parkinson's Disease Tutorial � University of Birmingham

� Biology of Parkinson's Disease � Science�Week Focus Report

� Fetal nerve cell transplantation: advances in the treamtent of Parkinson's Disease

� The Parkinson Alliance

� Parkinson's Disease: New Treatments Slow Onslaught of Symptoms

� Parkinson's Disease � Medline Plus

� Young Parkinson's Information and Referral Center � American Parkinson Disease Association

� Restless Legs Syndrome Foundation

� We Move

Sleep Disorders


� SleepNet

� Sleep Medicine Home Page

� The Sleep Well

� Talkaboutsleep.com

Tourette Syndrome

� Tourette Syndrome � from Neuroscience for Kids

� Tourette Syndrome Information� from NINDS, NIH

� Tourette Syndrome Home Page

� Tourette's Syndrome and Dopamine

Neuromuscular/Motor Neuron Disorders

� Amyotrophic Lateral Sclerosis

� NINDS Guillain�Barre Syndrome Fact Sheet

� Guillain�Barre Syndrome Foundation Intl.

� CMTnet: Charcot�Marie�Tooth Disease Information Exchange

� Muscular Dystrophy Association

� Muscular Dystrophy Association of Australia

� Spastic Paraplegia Foundation

Neuro�oncology

� National Neurofibromatosis Foundation

� Von Hippel�Lindau Disease (VHL) Family Alliance

� American Brain Tumor Association� ABTA

� ABTA Dictionary for brain tumor patients

� Brain Tumor Information � from the International Radiosurgery Association

Neuro�immunology

� Multiple Sclerosis � Neuroscience for Kids site


� Multiple Sclerosis Central

� Multiple Sclerosis Information for Physician and Medical Students

� Multiple Sclerosis Society of America

� MS page by Aapo Halko

� Myelin Project

Pediatric Neurology

� Autism � Neuroscience for Kids

� Dyslexia 2000 Network

� Cerebral Palsy � Hope Through Research � NINDS

� Child Neurology Page

Neuro�otology

� Meniere's disease

This site is maintained by Eric H. Chudler. Send questions and comments to [email protected] [Return to Neuroscience for Kids] | [Return to Eric H. Chudler's Home Page] [Useful UW Neuroscience Links] [Professional Organizations] [Government Agencies] [Neuroscience Education] [Grant and Funding Opportunities] [Commercial Neuroscience Resources] [Seattle Links] [Searching the Web] [Miscellaneous Links]


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