n e r v o u s s y s t e m

NERVOUS SYSTEM

Abalos, Ailyn

Juatas, Kenneth

Llorin, Patricia

Mansibang, Rania

Sunio, Leslie

DMD 1-F

Functions Of Nervous System

Communication and coordination

- Adapt and respond to changes from

both inside and outside the body

sends messages to the rest of the body

controls all of the body functions

Site of reasoning

The Organization of Nervous

System

Your nervous system has three

components…

Brain

- control center

Nerves

-carry messages

Spinal cord

-a thick bundle of nerves

Brain

Characteristics of the Brain

Weight: 1.3-kg (3-lb) mass of pinkish-gray jellylike tissue

Varies in gender:

Male: 1380 grams

Female: 1250 grams

With 100 billion nerve cell:

Neurons

Neuroglia (supporting-tissue) cells

4 types of Memory:

Short-term memory – when we say things over and

over again so you remember them.

Long term memory – we remember important

events or things that we do over and over again.

Ancestral Memory – We remember things right

when we were born. Example is when humans

remember how to get milk from their mom or feeding

bottles.

Eidetic Memory – a.k.a photographic memory

The Cranial Cavity

1. Meninges

Dura Mater - outermost membrane. The

toughest and thickest.

Arachnoid Layer - middle membrane.

Pia Mater - innermost membrane. Consists

of small blood vessels.

2. Cerebrospinal Fluid – A clear liquid that bathes the entire brain and fills a series of four cavities called ventricles

3. Gray Matter – Composed of Nerve cell bodies

4. White Matter – Composed of myelinated nerve fibers

5. Nucleus – Mass of nerve cells in any part of the brain and spinal cord.

6. Ganglion – Mass of nerve cell outside of the brain and spinal cord.

7. Commisure – Band of fibers joining corresponding opposite parts of the brain and spinal cord.

8. Brain:

Left and Right Brain Functions

The right brain is associated with artistic

ability like singing, painting, writing poetry,

etc.

Left-brain dominated people may find their

thought processes vague and difficult to

follow, for they are quite opposite in the way

they think. Left-brain dominated people tend

to be more logical and analytical in their

thinking and usually excel at mathematics and

word skills.

A. Embryological developmental of the Brain:

1. Forebrain - Prosencephalon

Telencephalon (Cerebrum)

Diencephalon (Thalamus and Hypothalamus)

2. Midbrain – Mesencephalon

Corpora Quadrigemina

Cerebral Peduncles

Iter (Cerebral aqueduct or aqueduct of Sylvius)

3. Hindbrain – Rhombencephalon

Metencephalon (cerebellum, pons varolii)

Myelencephalon (medulla oblongata)

5 Main Parts of the Brain

1. Cerebrum (Telencephalon)

2. Pons and Cerebellum (Metencephalon)

3. Midbrain (Mesencephalon)

4. Thalamus and Hypothalamus

(Diencephalon)

5. Medulla Oblongata (Myelencephalon)

1. Forebrain

Cerebrum (Telencephalon)

Cerebrum(the Latin word for brain)

a.k.a “cerebral cortex”

two large dome-shaped, almost symmetrical hemispheres

intelligence, memory and reason

Composed of gray matter thrown into infoldings: shallow; gyrusor gyri, deep; fissures

Innermost part is made of white matter

Great longitudinal fissure (or longitudinal cerebral fissure, or longitudinal fissure, or interhemispheric fissure) is the deep groove which separates the two hemispheres of the vertebrate brain.

•The cerebral cortex is made of grey matter, and

covers the cerebrum and cerebellum.

•The different lobes of the cerebral cortex subdivide

processing responsibilities based on sensory input

or motor function.

Fissures the Cerebrum:

1. Longitudinal Fissure – They are mirror twins

for motor and sensory activities of the body.

*Connected in the midline by corpus

callosum – allows the two cerebral

hemispheres to share learning and memory.

2. Lateral Fissure (Sylvian Fissure) – located

between frontal and parietal lobes. For speech

and hearing.

Corpus Callosum

•is a thick band of nerve fibers that

divides the cerebrum into left and

right hemispheres.

•It connects the left and right sides of

the brain allowing for communication

between both hemispheres.

•transfers motor, sensory, and

cognitive information between the

brain hemispheres.

3. Central Fissure (Rolandic Fissure) – Between

the frontal and parietal lobes; for both motor

and sensory functions.

4. Transverse Fissure – found between the

cerebrum and cerebellum.

5. Palate Occipital Fissure – between occipital

and parietal lobes.

Lobes of the Cerebrum

FRONTAL LOBE - involved

with decision-making,

problem solving, and

planning

Lobes of the Cerebrum

PARIETAL LOBE - receives

and processes sensory

information.

TEMPORAL LOBE (LEFT & RIGHT HEMISPHERE) - involved with emotional responses,

memory, and speech.

OCCIPITAL LOBE involved with vision

and color recognition.

Functions of the Cerebral Cortex

Determining Intelligence

Determining Personality

Thinking

Perceiving

Producing and Understanding Language

Interpretation of Sensory Impulses

Motor Function

Planning and Organization

Touch Sensation

Wernicke’s - language

comprehension

Primary auditory

cortex

auditory (sound) pitch

and volume.

Broca's area - speech

production, language

processing,

controls facial neurons

Motor cortex -

movements and

coordination.

Somatosensory cortex

processes input from the

various systems in the body

which are sensitive to touch.

(Sensations)

•The cerebral cortex is made of grey matter, and

covers the cerebrum and cerebellum.

•The different lobes of the cerebral cortex subdivide

processing responsibilities based on sensory input

or motor function.

Visual

Amygdala

It is a limbic system:

•Emotions

•Motivations

•Survival.

•Fear

•Anger

•Pleasure.

•Hormonal Secretions

•MemoryHippocampus

•Memory forming, organizing,

and storing.

•Connecting emotions and senses,

such as smell and sound, to

memories.

2. Hindbrain

Metencephalon:

A. Cerebellum

B. Pons Varolli

2. A Cerebellum“little brain”

two smaller hemispheres located at the back of the cerebrum

Oval in shape

Occupies the posterior cranial fossa

Seperated from the cerebrum by the tentorium cerbelli

The outer layer of the cerebellum consists of fine folds called folia.

the outer layer of cortical gray matter surrounds a deeper layer of white matter and nuclei (groups of nerve cells).

Three fiber bundles called cerebellar peduncles connect the cerebellum to the three parts of the brain stem.

Anterior Lobe – posture

Posterior Lobe – coordination of movement

Flocculonodular Lobe – equilibrium

Cerebellum

•The area of

the hindbrain that

controls motor

movement

coordination, balance,

equilibrium

and muscle tone.

The Brainstem

3 parts: midbrain, pons, and medulla oblongata

The brain stem is evolutionarily the most primitive part of the

brain and is responsible for sustaining the basic functions of

life, such as breathing and blood pressure.

A canal runs longitudinally through these structures carrying

cerebrospinal fluid.

Distributed along its length is a network of cells, referred to as

the reticular formation that governs the state of alertness.

Mammillary

body

-recognition

memory.

Pituitary Gland

•"master gland,"

•makes hormones

Pons

Reticular Formation

Spinal cord

Fornix

Hypothalamus

Functions:

• path for messages traveling between the

upper brain and spinal cord

• the seat of basic and vital functions such as

breathing, blood pressure, and heart rate, as

well as reflexes like eye movement and

vomiting.

Reticular Formation

is a netlike formation of nuclei known as the

reticular formation.

The reticular formation controls respiration,

cardiovascular function, digestion, levels of

alertness, and patterns of sleep.

It also determines which parts of the constant flow

of sensory information into the body are received

by the cerebrum.

Reticular Formation

Functions:

Sleep

Walking

Sex

Eating

Elimination

Behavioral motivation

Breathing

Beating of the heart

Control of Consciousness – most important

2.B Pons Varolli

slunted in front of the cerebellum between the midbrain and the medulla oblongata.

A bridge-like structure composed entirely of white matter

It joins the two haves of the cerebellum

Trigeminal Nerve (Cranial Nerve 5) emerges from pons

FUNCTION:

The pons serves mainly as a relay station linking

the cerebral cortex and the medulla oblongata.

Pons

•connects the cerebral cortex with

the medulla oblongata

•serves as a communications and

coordination center between the

two hemispheres of the brain

•As a part of the brainstem, it

helps in the transferring of

messages between various parts of

the brain and the spinal cord.

3. Midbrain

Mesencephalon

also called mesencephalon,

region of the developing

vertebrate brain containing cranial nerves that

stimulate the muscles controlling eye movement,

between the forebrain and hindbrain

Concerned with motor coordination

Connects the cerebellum with the cerebrum

Functions:

At the bottom of the

midbrain are reflex and

relay centers

relating to pain,

temperature, and touch,

as well as several regions

associated with the, such

as the red nucleus and

the

substantia nigra - for

reward, addiction, and

movement

A pair of nuclei

called the superior

colliculus

– Controls reflex

actions of the

eye, such as

blinking,

opening and

closing the pupil,

and focusing the

lens.

A second pair of

nuclei, called the

inferior colliculus,

– controls auditory

reflexes, such as

adjusting the ear

to the volume of

sound.

Sylvian/Cerebral

aqueduct/Iter

– canal that connects

the 3rd and 4th

ventricles of the

brain.

Cerebral Peduncles

– pair of cylindrical bodies

made up of nerve fibers

tracts which connect the

forebrain with the

hindbrain

- Bundle of Axons

Corpora

Quadrigemina

– 4 rounded

nuclear masses

Corpora quadrigeminaCerebral aqueduct

Central gray

stratum

Interpeduncular space

Substantia nigraRed nucleus of

tegmentum

4. MEDULLA OBLONGATA

Myelencephalon

lowest portion of the brainstem

At the top, it is continuous with the pons and the midbrain;

at the bottom, it makes a gradual transition into the spinal cord at the foramen magnum.

extends from the pons above and is continuous with the spinal cord below.

Pyramidal in shape (broad above and narrow below)

The nerve cells of the medulla are grouped to form “nuclei” out of which emerge cranial nerves 6-12.

Medulla oblongata

is a portion of the

hindbrain that

controls autonomic

functions:

•breathing,

•digestion,

•heart and blood

vessel

•swallowing

•sneezing

Functions:

Organ of conduction for the passage of impulses between

brain and spinal cord

Contains center for control of bodily functions:

• Cardiac Inhibitory Center – holds heart rate to slower rate

through cranial nerve 10 or Vagus Nerve.

• Vasoconstrictor Center – narrowing of lumen of the arteries

• Respiratory Center – controls rate and depth of respiration

• Reflex Center – sneezing, coughing, vomiting, winking and

the movements and secretions of the alimentary canal.

5. Diencephalon Thalamus and Hypothalamus

Diencephalon

A. Thalamus

large mass of gray matter

located in the cerebral

hemisphere.

acts as a relay station

between the cerebrum and

the rest of the brain and

spinal cord.

B. Hypothalamus

lies below the thalamus

contains temperature-

regulating mechanisms and

relations with the pituitary

gland.

hunger, thirst, defense

reactions; fear, rage and

satiety.

Thalamus

•It is involved in sensory perception

and regulation of motor functions.

•is a limbic system structure

•it connects areas of the cerebral

cortex that are involved in sensory

perception and movement

• controls sleep and awake states of

consciousness.

Limbic System

The limbic system is a group of brain

structures that plays a role in emotion,

memory, and motivation.

Hypothalamus

•plays a central role in

controlling our autonomous

nervous system (ANS),

•responsible for regulating

homeostatic metabolic processes

in the body.

•Examples of homeostatic

processes include sleeping,

eating, thirst, blood pressure,

body temperature, and

electrolyte balance.

Hypothalamus

-regulates hunger, thirst, sleep, body

temperature, sexual drive, and other

functions.

Fornix connects

the Hippocampus to

the Hypothalamus

Spinal Cord

a long, thin, tubular bundle

of nervous tissue and

support cells that extends

from the brain.

The spinal cord begins at

the Occipital bone and

extends down to the space

between the first and

second lumbar vertebrae.

It is around 45 cm (18 in)

in men and around 43 cm

(17 in) long in women.

Functions of Spinal Cord

Serve as a conduit for motor information,

which travels down the spinal cord

Serve as a conduit for sensory information,

which travels up the spinal cord.

Serve as a center for coordinating certain

reflexes.

Cervical Spinal Cord

Divided into eight

levels. Each level

contributes into

different functions in

the neck and arms.

Sensations from the

body are similarly

transported from the

skin and other areas of

the body from the

neck, shoulders, and

arms up to the brain.

Thoracic Spinal cord

The nerves of the

spinal cord supply

muscles of the chest

that help in breathing

and coughing.

This region also

contains nerves in the

sympathetic nervous

system.

Lumbosacral Spinal Cord

The lumbosacral

spinal cord and nerve

supply legs, pelvis,

and bowel and

bladder. Sensations

from the feet, legs,

pelvis, and lower

abdomen are

transmitted through

the lumbosacral nerves

and spinal cord to

higher segments and

eventually the brain

Peripheral Nervous System

- main function of the PNS is to connect

the central nervous system (CNS) to the

limbs and organs.

- peripheral nervous system of humans has

thirty-one pairs of spinal nerves,

CRANIAL NERVES

I. Olfactory NerveY

Function:

-Sense of Smell

- Sensory

Function:

Transmits visual information to the brain; Located in

Optic canal.

Sense of sight

III. OCCUMOTOR NERVE

Function:

The oculomotor

nerve is the third of

twelve paired cranial

nerves. It controls most

of the eye's movement

and constriction of the

pupil, and maintains an

open eyelid

IV. TROCHLEAR NERVEFunction:

It is a motor nerve which

stimulates and supplies the

superior oblique muscle of the

eye. The trochlear nerve is also

a part of the cranial nerves

which stems from the brain and

connects to the eyes. Trochlear

nerve function is interconnected

to the superior oblique muscle.

Which is also responsible for

the movement of the eyes as it

is one of the six extra ocular

muscles that together help in

the movement and alignment of

the eyes. It acts as a pulley to

move the eyes down—toward

the tip of the nose

Receives sensation

from the face and

innervates the muscles

of mastication.

Sensory and Motor

VI. ABDUCENS

Innervates the lateral

rectus, which abducts

the eye.

Motor

VII. FACIALProvides motor innervation to

the muscles of facial

expression, posterior belly of

the digastric muscle,

and stapedius muscle, receives

the special sense of taste from

the anterior 2/3 of the tongue,

and provides

secretomotor innervation to

the salivary glands (except

parotid) and the lacrimal gland;

Located and runs

through internal acoustic

canal to facial canal and exits

at stylomastoid foramen

VIII. VESTIBULOCOCHLEARFunction :

The vestibulocochlear

nerve has separate

acoustic and vestibular

divisions. The acoustic

portion of the nerve allows

for proper hearing. The

vestibular division is

essential for normal

balance.

IX. GLOSSOPHARYNGEAL

The glossopharyngeal

nerve allows for taste

on the back portion of

the tongue, provides

the sensations of pain

and touch from the

tongue and tonsils,

and participates in the

control of muscles

used during

swallowing

X. VAGUS

Function :

The vagus nerve plays

an important role in the

human body. It controls

the sensory and motor

functions of the heart

and glands. It also

participates in the

process of digestion.

XI. ACCESORYFunction:

The spinal accessory

nerve allows the

trapezius muscle and

sternocleidomastoid

muscle to control the

movements of the

head.

XII. HYPOGLOSSAL

Provides motor

innervation to the

muscles of the tongue

Important for

swallowing (bolus

formation) and speech

articulation.

Located

in hypoglossal canal.

Spinal Nerves

carries motor, sensory, and autonomic

signals between the spinal cord and the

body.

Humans have 31 left-right pairs of spinal

nerves, each roughly corresponding to a

segment of the vertebral column:

– 8 cervical spinal nerve pairs (C1-C8)

– 12 thoracic pairs (T1-T12)

– 5 lumbar pairs (L1-L5)

– 5 sacral pairs (S1-S5)

– 1 coccygeal pair.

Cervical nerves (innervate the neck and

the arms): cords conducting nerve impulses

from the neck and arms to the cerebellum

via the spinal cord.

Intercostal nerve: cord conducting nerve

impulses between the ribs.

Lumbar and sacral nerves (innervate the

legs and pelvic organs): nerves originating

in the lower back and extending into the

pelvis and legs.

Sacral plexus: network of nerves of the

sacrum.

Lumbar plexus: network of nerves of the

lower back.

Spinal cord: substance belonging to the

nervous system, found in the holes of the

vertebrae.

Brachial plexus: network of nerves of the

arm.

Cerebrum: seat of the mental capacities.

Cervical nerve

Lumbar and sacral nerves

The formation of the spinal nerve

from the dorsal and ventral roots

dorsal roots carry afferent sensory axons,

while the ventral roots

carry efferent motor axons.

Neuron

also known as neurone or nerve cell

basic unit of nervous system

Is an electircally excitable cell that

processes and transmits information by

electrical and chemical signaling.

there are billions neurons in the body. In

fact, there are 12 - 14 billlions of neurons in

one partof the brain alone.

Basic nerve cell structure

PARTS:Cell Body/ soma / perikaryon

=> the factory of the neuron. It produces all the

proteins for the dendrites, axons and synaptic

terminals.

Neuronal membrane

=> serves as a barrier to enclose the cytoplasm inside

the neuron, and to exclude certain substances that float

in the fluid that bathes the neuron.

Nodes of Ranvier

=> gaps between myelinated segment

Myelin Sheath

=> protects the axon, and prevents interference

between axons as they pass along in bundles,

sometimes thousands at time.

Axon=> transmit impulses away from the cell

body.

=>The main conducting unit of the neuron.

=>Conduct nerve impulses thru another

cells.

=>Capable of conveying electrical signals

along distances that range from as short as

0.1 mm to as long as 2 m.

Dendritesthe main apparatus for receiving signals from

other nerve cells.

The “ antennae” of the neuron.

They transmit impulses towards the cell body.

covered by thousands of synapses

200 000 axon terminals make contact with

dendrites of Purkinje neurons in

cerebellum.

diameter decrease from proximal to distal

end.

Nerve Ending (Presynaptic Terminals)

=> Synapses are the junctions formed with

other nerve cells where the presynaptic

terminal of one cell comes into 'contact'

with the postsynaptic membrane of another.

It is at these junctions that neurons are

excited, inhibited, or modulated.

Types of SynapsesElectrical synapses

Occur where the presynaptic terminal is in electrical

continuity with the postsynaptic. Ions and small

molecules passing through, thus connecting channels

from one cell to the next, so that electrical changes in

one cell are transmitted almost instantaneously to the

next. Ions can generally flow both ways at these

junctions i.e. they tend to be bi-directional, although

there are electrical junctions where the ions can only

flow one way, these are know as rectifying junctions.

Rectifying junctions are used to synchronise the

firing of nerve cells.

Chemical synaptic junction is more

complicated. The gap between the post- and

presynaptic terminals is larger, and the mode

of transmission is not electrical, but carried by

neurotransmitters, neuroactive substances

released at the presynaptic side of the

junction.

a. Type I is an excitatory synapse,

generally found on dendrites

b. type II is an inhibitory synapse,

generally found on cell bodies

Transmission of signals…

SYNAPSE

Also known as the neuromuscular junction

A structure that permits a neuron to pass an

electrical or chemical signal to another cell.

a place in the body where the axons of motor

nerves meet the muscle, thus transmitting

messages from the brain which cause the muscle

to contract and relax.

neuromuscular junctions control the movements of

the body and cause the heart to beat.

SYNAPSE

Classification of neuron according to the

Direction:

Afferent neurons convey information from

tissues and organs into the central nervous

system and are sometimes also called

sensory neurons.

Efferent neurons transmit signals from the

central nervous system to the effector cells

and are sometimes called motor neurons.

Interneurons connect neurons within

specific regions of the central nervous

system.

Classification of neurons according to their

functions:

motor neurons : control muscle fibers or

effecteral organs eg: endocrine.

sensory neurons : receive sensory stimuli.

sensory

neuronerelay

neurone

motor

neurone

Sensory neurons

Carries impulses from receptors e.g pain receptors in skin to the CNS( brain or spinal cord)

Relay neuron

Carries impulses from sensory nerves to motor nerves

Motor neuron

Carries impulses from CNS to effector e.g. muscle to bring about movement or gland to bring about secretion of hormone e.g ADH

NEUROGLIA

smallest cells of nervous tissue

Function : metabolic, support, n protection.

2 types Neuroglial Cells

1. Macroglial

2. Microglial

1. Macroglial

A. Astrocyte

– largest

- long processes

- processes of the astrocytes are also

present at the periphery of the brain and

spinal cord forming a layer under pia mater

: separates conn. Tissue of pia mater from

the nerve cells.

Types of astrocyte

a1. protoplasmic : in grey matter of brain n

spinal cord

:processes are shorter and

thicker

a2. fibrous : in white matter

: long smooth processes

B. Oligodendrocytes

– smaller than astrocytes

- lesser processes n shorter

- can be found both in grey n white matter.

Function:

1. take part in metabolism of neurons

2. form protective barrier around neurons.

C. Ependimocytes

– looks like an epithelial layer.

- line the central canal of spinal cord n

ventricles of the brain which are filled with

cerebrospinal fluid.

- take part in elaboration of cerebrospinal

fluid.

- serve as a barrier btw fluid and neural

elements.

- at last they form supporting framework of

the system.

2. Microglia

– small cells, highly-densed elongated bodies

n short processes with numerous small

branches.

- condensed, elongated nucleus.

- in adults, microglia are derived from

monocytes of the bone marrow blood n they

are phagocytes.

Somatic Nervous System

> part of the PNS associated with the

voluntary control of body movements via skeletal

muscles.

> It is consists of efferent nerves responsible for

stimulating muscle contraction, including all the

non sensory neurons connected with

skeletal muscles and skin.

> Its Sensory axon carries signals inward from

receptors in the skin, skeletal muscles, and

tendons while its motor axons carries signals out

to the body’s skeletal muscles.

Autonomic Nervous Systemthe part of the PNS that acts as a control

system functioning largely below the level of

consciousness.

It controls visceral functions.

The ANS affects heart rate, digestion, respiration

rate, salivation, perspiration, diameter of the

pupils, micturition (urination), and sexual arousal.

Whereas most of its actions are involuntary, some,

such as breathing, work in tandem with the conscious

mind.

Its sensory and motor axon carry signals from and to

smooth muscles, cardiac (heart) muscle, and the

different regions inside the body.

Division of Autonomic Nervous System

Parasympathetic Nervous System

The parasympathetic system specifically is

responsible for stimulation of "rest-and-digest"

activities that occur when the body is at rest,

including sexual

arousal, salivation, lacrimation (tears), urination, d

igestion, and defecation

Sympathetic Nervous System

Its general action is to mobilize the body's

resources under stress; to induce the fight-or-flight

response. It is, however, constantly active at a

basal level to maintain homeostasis.