chapter 33 nervous system
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Chapter 33 Nervous System
Section 1: Structure of the Nervous System
Section 2: Organization of the Nervous System
Section 3: The Senses
Section 4: Effects of Drugs
Neurons
Neurons are specialized nerve cells that help you gather information about your environment, interpret the information, and react to it.
33.1 Structure of the Nervous System
Nervous System
Neurons consist of three main regions: the dendrites, a cell body, and an axon.
Chapter 33
Dendrites pass signals they receive on to the cell body in electrical impulses.
Nervous System
The axon passes those impulses on to the other neurons or muscles.
33.1 Structure of the Nervous System
Chapter 33
There are three kinds of neurons: sensory neurons, interneurons, and motor neurons.
Nervous System
Sensory neurons send impulses from receptors in the skin and sense organs to the brain and spinal cord.
Interneurons carry impulses to motor organs.
33.1 Structure of the Nervous System
Chapter 33
Nervous System
33.1 Structure of the Nervous System
Motor neurons carry impulses away from the brain and spinal cord to a gland or muscles, resulting in a secretion
or movement. The nerve impulse
completes a reflex arc, or a nerve pathway thatconsists of a sensory neuron, an interneuron, and a motor neuron.
Chapter 33
A Nerve Impulse
Nervous System
Neurons at rest do not conduct impulses.
Sodium ions (Na+) collect on the outside of the cell membrane.
33.1 Structure of the Nervous System
Chapter 33
Potassium ions (K+) collect on the inside of the cell membrane.
Nervous System
33.1 Structure of the Nervous System
Negatively charged proteins actively transport sodium ions out of the cell andpotassium ions into the cell.
Chapter 33
An Action Potential
Nervous System
A nerve impulse is also known as an action potential.
The minimum stimulus to cause an action potential to be produced is called a threshold.
33.1 Structure of the Nervous System
Chapter 33
When a stimulus reaches threshold, channels open in the plasma membrane.
Nervous System
Sodium ions are rapidly pumped through these channels causing a temporary change in the electrical charges.
More positive charges are now inside the membrane.
33.1 Structure of the Nervous System
Chapter 33
The now positive charge inside the membrane causes other channels to open and the potassium is quickly pumped out of the cell.
Nervous System
The potassium restores the positive charge outside the cell.
33.1 Structure of the Nervous System
Chapter 33
This rapid positive to negative to positive charge reversal moves along the axon like a wave.
Nervous System
The movement can be seen by finding the sodium-potassium reversal pattern in the three diagrams.
33.1 Structure of the Nervous System
Chapter 33
Nodes along the axon allow ions to pass through the myelin layer to the plasma membrane.
Nervous System
The ions jump from node to node and increase the speed of the impulse.
Speed of an Action Potential
33.1 Structure of the Nervous System
Visualizing Action Potential
Chapter 33
The small gap between the axon of one neuron and the dendrite of another neuron is called a synapse.
Nervous System
An action potential is carried across these gaps by neurotransmitters.
The Synapse
33.1 Structure of the Nervous System
Chapter 33
Nervous SystemChapter 33
The nervous system consists of two major divisions: the central nervous system and the peripheral nervous system.
33.2 Organization of the Nervous System
Nervous SystemChapter 33
The Central Nervous System
Nervous System
The central nervous system (CNS) is made up mostly of interneurons.
Coordinates all of the body’s activities
Relays messages, processes information, and analyzes responses
33.2 Organization of the Nervous System
Chapter 33
The Brain
Nervous System
The brain is sometimes called the control center of the entire body.
Divided into the cerebrum, the cerebellum, and the brain stem.
33.2 Organization of the Nervous System
Chapter 33
The cerebrum is divided into two halves called the left and right hemispheres.
Nervous System
The functions of the brain include thought processes (learning), memory, language, speech, voluntary body movements, and sensory perception.
33.2 Organization of the Nervous System
Chapter 33
The cerebellum controls balance, posture, and coordination.
Nervous System
The skeletal muscles are controlled to make your motor skills coordinated and smooth.
33.2 Organization of the Nervous System
Chapter 33
The brain stem connects the brain and spinal cord and is composed of the medulla oblongata and the pons.
Nervous System
The medulla oblongata helps control breathing rate, heart rate, and blood pressure.
The pons also aids in breathing.
33.2 Organization of the Nervous System
Chapter 33
The hypothalamus, located between the brain stem and the cerebrum, is essential for homeostasis.
Nervous System
Regulates body temperature, thirst, appetite, and water balance.
33.2 Organization of the Nervous System
Chapter 33
The Spinal Cord
Nervous System
Nerve column that extends from the brain to the lower back.
Protected by the vertebrae
Processes reflexes
33.2 Organization of the Nervous System
Chapter 33
The Peripheral Nervous System
Nervous System
A nerve is a bundle of axons and may contain sensory and motor neurons.
The peripheral nervous system (PNS) contains all the neurons that are not part of the central nervous system.
33.2 Organization of the Nervous System
Chapter 33
The Somatic Nervous System
Nervous System
Nerves in the somatic nervous system relay information from external sensory receptors to the central nervous system, and motor nerves relay information from the central nervous system to skeletal muscles.
Voluntary movements and reflexes are a part of the somatic nervous system.
33.2 Organization of the Nervous System
Chapter 33
The Autonomic Nervous System
Nervous System
The autonomic nervous system carries impulses from the central nervous system to the heart and other internal organs.
The body responds involuntarily, not under conscious control.
33.2 Organization of the Nervous System
Chapter 33
There are two branches of the autonomic nervous system.
Nervous System
The sympathetic nervous system is most active in times of emergency or stress when the heart rate and breathing rate increase.
The parasympathetic nervous system is most active when the body is relaxed.
33.2 Organization of the Nervous System
Chapter 33
Nervous SystemChapter 33
Taste and Smell
Specialized neurons in your body enable you to taste, smell, hear, see, and touch, and to detect motion and temperature.
33.3 The Senses
Nervous System
Taste buds detect combinations of chemicals that we identify as sweet, sour, salty, and bitter.
Chapter 33
Receptors associated with taste and smell are located in the mouth and nasal cavity.
Nervous System
33.3 The Senses
Signals from these receptors work together to createa combined effect in the brain.
Chapter 33
Sight
Light travels through the cornea and the pupil to the lens.
Nervous System
The lens focuses the image on the retina.
33.3 The Senses
Rods and cones in the retina providelight-sensitivity and information about color.
Chapter 33
Hearing
Nervous System
33.3 The Senses
Sound waves enter the auditory canal andcause a membrane, called the tympanum, at the end of the ear canal to vibrate.
These vibrationscause the cochlea to generate nerve impulses that are interpreted by the brain.
Chapter 33
Balance The semicircular canals, located in the
inner ear, transmit information about body position and balance to the brain.
Nervous System
33.3 The Senses
Chapter 33
Touch
Many types of sensory receptors that respond to temperature, pressure, and pain are found in the epidermis and dermis layers of the skin.
Nervous System
33.3 The Senses
Chapter 33
How Drugs Work
A drug is a substance, natural or artificial, that alters the function of the body.
33.4 Effects of Drugs
Nervous SystemChapter 33
Nervous SystemChapter 33
Some drugs affect the nervous system in the following ways:
Nervous System
can cause an increase in the amount of a neurotransmitter that is released into a synapse
can block a receptor site on a dendrite, preventing a neurotransmitter from binding
can prevent a neurotransmitter from leaving a synapse
can imitate a neurotransmitter
33.4 Effects of Drugs
Chapter 33
Nervous System
33.4 Effects of Drugs
Many drugs that affect the nervous systeminfluence the level of a neurotransmitter called dopamine.
Normally, dopamine is removed from a synapse by beingreabsorbed by the neuron that released it.
Chapter 33
Nervous System
Classes of Commonly Abused Drugs
Stimulants
Drugs that increase alertness and physical activity
Nicotine
Caffeine
33.4 Effects of Drugs
Chapter 33
Nervous System
Depressants
Drugs that tend to slow down the central nervous system
Alcohol
Inhalants
Illegal drugs
33.4 Effects of Drugs
Chapter 33
Nervous System
Tolerance and Addiction
Tolerance occurs when a person needs more and more of the same drug to get the same effect.
The psychological and/or physiological dependence on a drug is addiction.
33.4 Effects of Drugs
Chapter 33
Nervous System
Chapter Resource Menu
Chapter Diagnostic Questions
Formative Test Questions
Chapter Assessment Questions
Standardized Test Practice
biologygmh.com
Glencoe Biology Transparencies
Image Bank
Vocabulary
AnimationClick on a hyperlink to view the corresponding lesson.
Chapter 33
Which is not one of the main parts of a neuron?
A. axon
B. cell body
C. dendrites
D. nucleus
Nervous System
Chapter Diagnostic Questions
Chapter 33
Another name for a nerve impulse is _______.
A. synapse
B. threshold
C. reflex arc
D. action potential
Nervous System
Chapter Diagnostic Questions
Chapter 33
What occurs when a motor neuron synapses with a muscle cell?
A. muscle contracts
B. muscle relaxes
C. pain
D. numbness
Nervous System
Chapter Diagnostic Questions
Chapter 33
What type of neuron begins a reflex arc?
A. interneuron
B. motor neuron
C. sensory neuron
D. transmitter neuron
Nervous System
33.1 Formative Questions
Chapter 33
What is another name for nerve impulse?
A. synapsis
B. threshold
C. action potential
D. neurotransmitter
Nervous System
33.1 Formative Questions
Chapter 33
Nervous System
True or False
A stronger stimulus will cause a stronger action potential.
33.1 Formative Questions
Chapter 33
Nervous System
When a neuron is at rest, what maintains the high concentration gradients of potassium ions inside the cell and sodium ions outside the cell?
33.1 Formative Questions
Chapter 33
Nervous System
A. diffusion
B. osmosis
C. active transport
D. ion channels
33.1 Formative Questions
Chapter 33
Nervous System
Which is not part of the central nervous system?
A. brain
B. spinal cord
C. interneurons
D. sensory neurons
33.2 Formative Questions
Chapter 33
Nervous System
What does the cerebrum regulate?
A. breathing and heart rates
B. complex motor skills
C. sleep, aggression, and fear
D. voluntary body movements
33.2 Formative Questions
Chapter 33
Nervous System
True or False
Some reflexes are processed only in the spinal cord and do not need input from the brain.
33.2 Formative Questions
Chapter 33
Nervous System
What is a nerve?
A. a bundle of axons
B. a chain of neurons
C. a sensory synapse
D. a series of impulses
33.2 Formative Questions
Chapter 33
Nervous System
What part of the nervous system is usually under voluntary control?
A. autonomic nervous system
B. somatic nervous system
C. sympathetic nervous system
D. parasympathetic nervous system
33.2 Formative Questions
Chapter 33
Nervous System
What are sensory receptors?
33.3 Formative Questions
A. cells that create action potentials andthresholds
B. localized areas of the central nervoussystem
C. chemicals that cross a synapse betweentwo nerve cells
D. specialized neurons for detecting the world around you
Chapter 33
Nervous System
Which part of the eye contains light-detecting receptors?
33.3 Formative Questions
Chapter 33
Nervous System
What is the function of the optic nerve?
A. It forms a visual image.
B. It controls the muscles of the iris.
C. It interprets light intensity and colors.
D. It sends action potentials to the brain.
33.3 Formative Questions
Chapter 33
Nervous System
Where are sound vibrations converted into nerve impulses?
33.3 Formative Questions
Chapter 33
Nervous System
Where are the sensory receptors that detect your body’s position and motion?
33.3 Formative Questions
Chapter 33
Nervous System
Why is caffeine a drug?
A. It is a depressant.
B. It is an artificial substance.
C. It influences the nervous system.
D. It builds tolerance to its effects.
33.4 Formative Questions
Chapter 33
Nervous System
Which neurotransmitter is influenced by nicotine and amphetamines, and is involved with most types of addiction?
A. adenosine
B. dopamine
C. epinephrine
D. serotonin
33.4 Formative Questions
Chapter 33
Nervous System
Which is not a stimulant?
A. alcohol
B. caffeine
C. nicotine
D. methamphetamine
33.4 Formative Questions
Chapter 33
Nervous System
What is the term for the body’s decreased response to a drug?
A. addiction
B. dependence
C. tolerance
D. withdrawal
33.4 Formative Questions
Chapter 33
Nervous System
When people who are addicted try to quit, why is it difficult to resist going back to the drug?
A. Adenosine levels increase.
B. Dopamine levels decrease.
C. The central nervous system slows down.
33.4 Formative Questions
D. Action potentials in neurons becomestronger.
Chapter 33
Nervous System
True or False
Physiological dependence on a drug is stronger than psychological dependence.
33.4 Formative Questions
Chapter 33
Name the part of the brain that is responsible for memory.
A. hypothalamus
B. medulla oblongata
C. cerebrum
D. cerebellum
Nervous System
Chapter Assessment Questions
Chapter 33
Contrast the functions of the cerebellum and the cerebrum.
Nervous System
Answer: The cerebellum controls balance,coordination, and motor skills. The cerebrum controls learning, memory, speech, voluntary body movements, and sensory perception.
Chapter Assessment Questions
Chapter 33
What part of the brain is identified in the image?
A. pons
B. cerebrum
C. hypothalamus
D. medulla oblongata
Nervous System
Chapter Assessment Questions
Chapter 33
How do nerve impulses travel in a neuron?
Nervous System
A. dendrite cell body axon
B. dendrite cell body axon
C. dendrite cell body axon
Standardized Test Practice
Chapter 33
What carries signals from the axon of one neuron to the dendrite of another neuron?
Nervous System
A. interneurons
B. ion channels
C. neural nodes
D. neurotransmitters
Standardized Test Practice
Chapter 33
Which word best describes the hypothalamus?
Nervous System
A. processor
B. reflexor
C. regulator
D. transmitter
Standardized Test Practice
Chapter 33
What part of the brain is highly developed in animals that have finely tuned balance and complex coordination?
Nervous System
A. cerebellum
B. medulla
C. thalamus
D. temporal lobe
Standardized Test Practice
Chapter 33
How do the sympathetic and parasympathetic nervous systems act together?
Nervous System
A. They send and receive neurotransmitters.
Standardized Test Practice
B. They send opposing signals to the sameorgans.
C. They balance voluntary and involuntaryresponses.
D. They receive the same impulses from different receptors.
Chapter 33
Why is this receptor located closest to the surface of the skin?
Nervous System
Standardized Test Practice
Chapter 33
Nervous System
A. It detects cold.
B. It detects heat.
C. It detects heavy pressure.
D. It detects light touch.
Standardized Test Practice
Chapter 33
What substances in the body are most closely associated with a drug’s influence on the nervous system?
Nervous System
A. endorphins
B. Na+ and K+ ions
C. neurotransmitters
D. proteins
Standardized Test Practice
Chapter 33
Where in the nerve pathway do drugs have their primary effect?
Nervous System
A. axons
B. dendrites
C. synapses
D. myelin sheaths
Standardized Test Practice
Chapter 33
Which step is blocked by cocaine?
Nervous System
Standardized Test Practice
Chapter 33
Glencoe Biology Transparencies
Nervous SystemChapter 33
Image Bank
Nervous SystemChapter 33
neuron
dendrite
cell body
axon
reflex arc
action potential
threshold
node
synapse
neurotransmitter
Nervous System
Vocabulary
Section 1
Chapter 33
central nervous
system
peripheral nervous
system
cerebrum
medulla oblongata
pons
hypothalamus
somatic nervous
system
autonomic nervous
system
sympathetic
nervous system
parasympathetic
nervous system
Nervous System
Vocabulary
Section 2
Chapter 33
taste bud
lens
retina
rods
cochlea
semicircular canal
Nervous System
Vocabulary
Section 3
Chapter 33
drug
dopamine
stimulant
depressant
tolerance
addiction
Nervous System
Vocabulary
Section 4
Chapter 33
Chapter 33 Nervous System
Animation
Visualizing Action Potential
Impulse Movement
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