2. 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

3. Chapter 33
Nervous System
33.1 Structure of the Nervous System
Neurons
Neurons are specialized nerve cells that help you gather information about your environment, interpret the information, and react to it.
Neurons consist of three main regions: the dendrites, a cell body, and an axon.

4. The axon passes those impulses on to the other neurons or muscles.
Chapter 33
Nervous System
33.1 Structure of the Nervous System
Dendrites pass signals they receive on to the cell body in electrical impulses.
The axon passes those impulses on to the other neurons or muscles.

5. Interneurons carry impulses to motor organs.
Chapter 33
Nervous System
33.1 Structure of the Nervous System
There are three kinds of neurons: sensory neurons, interneurons, and motor neurons.
Sensory neurons send impulses from receptors in the skin and sense organs to the brain and spinal cord.
Interneurons carry impulses to motor organs.

6. resulting in a secretion or movement.
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 that
consists of a sensory neuron, an interneuron,
and a motor neuron.

7. Neurons at rest do not conduct impulses.
Chapter 33
Nervous System
33.1 Structure of the Nervous System
A Nerve Impulse
Neurons at rest do not conduct impulses.
Sodium ions (Na+) collect on the outside of the cell membrane.

8. Potassium ions (K+) collect on the inside of the cell membrane.
Chapter 33
Nervous System
33.1 Structure of the Nervous System
Potassium ions (K+) collect on the inside of the cell membrane.
Negatively charged proteins actively transport sodium ions out of the cell and
potassium ions into the cell.

9. A nerve impulse is also known as an action potential.
Chapter 33
Nervous System
33.1 Structure of the Nervous System
An Action Potential
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.

10. 33.1 Structure of the Nervous System
Chapter 33
Nervous System
33.1 Structure of the Nervous System
When a stimulus reaches threshold, channels open in the plasma membrane.
Sodium ions are rapidly pumped through these channels causing a temporary change in the electrical charges.
More positive charges are now inside the membrane.

11. The potassium restores the positive charge outside the cell.
Chapter 33
Nervous System
33.1 Structure of the Nervous System
The now positive charge inside the membrane causes other channels to open and the potassium is quickly pumped out of the cell.
The potassium restores the positive charge outside the cell.

12. Chapter 33
Nervous System
33.1 Structure of the Nervous System
This rapid positive to negative to positive charge reversal moves along the axon like a wave.
The movement can be seen by finding the sodium-potassium reversal pattern in the three diagrams.

13. Speed of an Action Potential
Chapter 33
Nervous System
33.1 Structure of the Nervous System
Speed of an Action Potential
Nodes along the axon allow ions to pass through the myelin layer to the plasma membrane.
The ions jump from node to node and increase the speed of the impulse.
Visualizing Action Potential

14. An action potential is carried across these gaps by neurotransmitters.
Chapter 33
Nervous System
33.1 Structure of the Nervous System
The Synapse
The small gap between the axon of one neuron and the dendrite of another neuron is called a synapse.
An action potential is carried across these gaps by neurotransmitters.

15. Chapter 33
Nervous System

16. Chapter 33
Nervous System
33.2 Organization of the Nervous System
The nervous system consists of two major divisions: the central nervous system and the peripheral nervous system.

17. The Central Nervous System
Chapter 33
Nervous System
33.2 Organization of the Nervous System
The Central 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

18. The brain is sometimes called the control center of the entire body.
Chapter 33
Nervous System
33.2 Organization of the Nervous System
The Brain
The brain is sometimes called the control center of the entire body.
Divided into the cerebrum, the cerebellum, and the brain stem.

19. Chapter 33
Nervous System
33.2 Organization of the Nervous System
The cerebrum is divided into two halves called the left and right hemispheres.
The functions of the brain include thought processes (learning), memory, language, speech, voluntary body movements, and sensory perception.

20. The cerebellum controls balance, posture, and coordination.
Chapter 33
Nervous System
33.2 Organization of the Nervous System
The cerebellum controls balance, posture, and coordination.
The skeletal muscles are controlled to make your motor skills coordinated and smooth.

21. The pons also aids in breathing.
Chapter 33
Nervous System
33.2 Organization of the Nervous System
The brain stem connects the brain and spinal cord and is composed of the medulla oblongata and the pons.
The medulla oblongata helps control breathing rate, heart rate, and blood pressure.
The pons also aids in breathing.

22. Regulates body temperature, thirst, appetite, and water balance.
Chapter 33
Nervous System
33.2 Organization of the Nervous System
The hypothalamus, located between the brain stem and the cerebrum, is essential for homeostasis.
Regulates body temperature, thirst, appetite, and water balance.

23. Nerve column that extends from the brain to the lower back.
Chapter 33
Nervous System
33.2 Organization of the Nervous System
The Spinal Cord
Nerve column that extends from the brain to the lower back.
Protected by the vertebrae
Processes reflexes

24. The Peripheral Nervous System
Chapter 33
Nervous System
33.2 Organization of the Nervous System
The Peripheral 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.

25. The Somatic Nervous System
Chapter 33
Nervous System
33.2 Organization of the Nervous System
The Somatic 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.

26. The Autonomic Nervous System
Chapter 33
Nervous System
33.2 Organization of the Nervous System
The Autonomic 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.

27. There are two branches of the autonomic nervous system.
Chapter 33
Nervous System
33.2 Organization of the Nervous System
There are two branches of the autonomic 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.

28. Chapter 33
Nervous System

29. Chapter 33
Nervous System
33.3 The Senses
Taste and Smell
Specialized neurons in your body enable you to taste, smell, hear, see, and touch, and to detect motion and temperature.
Taste buds detect combinations of chemicals that we identify as sweet, sour, salty, and bitter.

30. Signals from these receptors work together to create
Chapter 33
Nervous System
33.3 The Senses
Receptors associated with taste and smell are located in the mouth and nasal cavity.
Signals from these receptors work together to create
a combined effect in the brain.

31. Light travels through the cornea and the pupil to the lens.
Chapter 33
Nervous System
33.3 The Senses
Sight
Light travels through the cornea and the pupil to the lens.
The lens focuses the image on the retina.
Rods and cones in the retina provide
light-sensitivity and information about color.

32. Sound waves enter the auditory canal and cause a membrane,
Chapter 33
Nervous System
33.3 The Senses
Hearing
Sound waves enter the auditory canal and
cause a membrane,
called the tympanum,
at the end of the ear
canal to vibrate.
These vibrations
cause the cochlea to generate nerve impulses
that are interpreted by the brain.

33. Chapter 33
Nervous System
33.3 The Senses
Balance
The semicircular canals, located in the inner ear, transmit information about body position and balance to the brain.

34. Chapter 33
Nervous System
33.3 The Senses
Touch
Many types of sensory receptors that respond to temperature, pressure, and pain are found in the epidermis and dermis layers of the skin.

35. Chapter 33
Nervous System
33.4 Effects of Drugs
How Drugs Work
A drug is a substance, natural or artificial, that alters the function of the body.

36. Chapter 33
Nervous System

37. Some drugs affect the nervous system in the following ways:
Chapter 33
Nervous System
33.4 Effects of Drugs
Some drugs affect the nervous system in the following ways:
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

38. Many drugs that affect the nervous system influence the level of
Chapter 33
Nervous System
33.4 Effects of Drugs
Many drugs that affect the nervous system
influence the level of
a neurotransmitter
called dopamine.
Normally, dopamine is removed from a synapse by being
reabsorbed by the neuron that released it.

39. Classes of Commonly Abused Drugs
Chapter 33
Nervous System
33.4 Effects of Drugs
Classes of Commonly Abused Drugs
Stimulants
Drugs that increase alertness and physical activity
Nicotine
Caffeine

40. Drugs that tend to slow down the central nervous system
Chapter 33
Nervous System
33.4 Effects of Drugs
Depressants
Drugs that tend to slow down the central nervous system
Alcohol
Inhalants
Illegal drugs

41. Tolerance and Addiction
Chapter 33
Nervous System
33.4 Effects of Drugs
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.

42. Chapter Resource Menu Chapter Diagnostic Questions
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
Animation
Click on a hyperlink to view the corresponding lesson.

43. Which is not one of the main parts of a neuron?
Chapter 33
Nervous System
Chapter Diagnostic Questions
Which is not one of the main parts of
a neuron?
axon
cell body
dendrites
nucleus

44. Another name for a nerve impulse is _______.
Chapter 33
Nervous System
Chapter Diagnostic Questions
Another name for a nerve impulse
is _______.
synapse
threshold
reflex arc
action potential

45. What occurs when a motor neuron synapses with a muscle cell?
Chapter 33
Nervous System
Chapter Diagnostic Questions
What occurs when a motor neuron
synapses with a muscle cell?
muscle contracts
muscle relaxes
pain
numbness

46. What type of neuron begins a reflex arc?
Chapter 33
Nervous System
33.1 Formative Questions
What type of neuron begins a reflex arc?
interneuron
motor neuron
sensory neuron
transmitter neuron

47. What is another name for nerve impulse?
Chapter 33
Nervous System
33.1 Formative Questions
What is another name for nerve impulse?
synapsis
threshold
action potential
neurotransmitter

48. A stronger stimulus will cause a stronger action potential.
Chapter 33
Nervous System
33.1 Formative Questions
True or False
A stronger stimulus will cause a stronger
action potential.

49. the high concentration gradients of potassium ions inside the cell and
Chapter 33
Nervous System
33.1 Formative Questions
When a neuron is at
rest, what maintains
the high concentration
gradients of potassium
ions inside the cell and
sodium ions outside
the cell?

50. diffusion osmosis active transport ion channels
Chapter 33
Nervous System
33.1 Formative Questions
diffusion
osmosis
active transport
ion channels

51. Which is not part of the central nervous system?
Chapter 33
Nervous System
33.2 Formative Questions
Which is not part of the central nervous
system?
brain
spinal cord
interneurons
sensory neurons

52. What does the cerebrum regulate?
Chapter 33
Nervous System
33.2 Formative Questions
What does the cerebrum regulate?
breathing and heart rates
complex motor skills
sleep, aggression, and fear
voluntary body movements

53. Some reflexes are processed only in the
Chapter 33
Nervous System
33.2 Formative Questions
True or False
Some reflexes are processed only in the
spinal cord and do not need input from the
brain.

54. What is a nerve? a bundle of axons a chain of neurons
Chapter 33
Nervous System
33.2 Formative Questions
What is a nerve?
a bundle of axons
a chain of neurons
a sensory synapse
a series of impulses

55. What part of the nervous system is usually under voluntary control?
Chapter 33
Nervous System
33.2 Formative Questions
What part of the nervous system is usually
under voluntary control?
autonomic nervous system
somatic nervous system
sympathetic nervous system
parasympathetic nervous system

56. What are sensory receptors?
Chapter 33
Nervous System
33.3 Formative Questions
What are sensory receptors?
cells that create action potentials and
thresholds
localized areas of the central nervous
system
chemicals that cross a synapse between
two nerve cells
specialized neurons for detecting the
world around you

57. Which part of the eye contains light- detecting receptors?
Chapter 33
Nervous System
33.3 Formative Questions
Which part of the eye contains light-
detecting receptors?

58. What is the function of the optic nerve?
Chapter 33
Nervous System
33.3 Formative Questions
What is the function of the optic nerve?
It forms a visual image.
It controls the muscles of the iris.
It interprets light intensity and colors.
It sends action potentials to the brain.

59. Where are sound vibrations converted into nerve impulses?
Chapter 33
Nervous System
33.3 Formative Questions
Where are sound vibrations converted
into nerve impulses?

60. Where are the sensory receptors that
Chapter 33
Nervous System
33.3 Formative Questions
Where are the sensory receptors that
detect your body’s position and motion?

61. It is an artificial substance. It influences the nervous system.
Chapter 33
Nervous System
33.4 Formative Questions
Why is caffeine a drug?
It is a depressant.
It is an artificial substance.
It influences the nervous system.
It builds tolerance to its effects.

62. Which neurotransmitter is influenced by
Chapter 33
Nervous System
33.4 Formative Questions
Which neurotransmitter is influenced by
nicotine and amphetamines, and is involved
with most types of addiction?
adenosine
dopamine
epinephrine
serotonin

63. Which is not a stimulant?
Chapter 33
Nervous System
33.4 Formative Questions
Which is not a stimulant?
alcohol
caffeine
nicotine
methamphetamine

64. What is the term for the body’s decreased response to a drug?
Chapter 33
Nervous System
33.4 Formative Questions
What is the term for the body’s decreased
response to a drug?
addiction
dependence
tolerance
withdrawal

65. When people who are addicted try to quit, why
Chapter 33
Nervous System
33.4 Formative Questions
When people who are addicted try to quit, why
is it difficult to resist going back to the drug?
Adenosine levels increase.
Dopamine levels decrease.
The central nervous system slows down.
Action potentials in neurons become
stronger.

66. Physiological dependence on a drug is
Chapter 33
Nervous System
33.4 Formative Questions
True or False
Physiological dependence on a drug is
stronger than psychological dependence.

67. Name the part of the brain that is responsible for memory.
Chapter 33
Nervous System
Chapter Assessment Questions
Name the part of
the brain that is
responsible for
memory.
hypothalamus
medulla oblongata
cerebrum
cerebellum

68. Contrast the functions of the cerebellum and the cerebrum.
Chapter 33
Nervous System
Chapter Assessment Questions
Contrast the functions of the cerebellum
and the cerebrum.
Answer: The cerebellum controls balance,
coordination, and motor skills.
The cerebrum controls learning,
memory, speech, voluntary body
movements, and sensory
perception.

69. What part of the brain is identified in the image? pons cerebrum
Chapter 33
Nervous System
Chapter Assessment Questions
What part of the
brain is identified in
the image?
pons
cerebrum
hypothalamus
medulla oblongata

70. How do nerve impulses travel in a neuron?
Chapter 33
Nervous System
Standardized Test Practice
How do nerve impulses travel in a neuron?
dendrite cell body axon
dendrite cell body axon
dendrite cell body axon

71. What carries signals from the axon of one
Chapter 33
Nervous System
Standardized Test Practice
What carries signals from the axon of one
neuron to the dendrite of another neuron?
interneurons
ion channels
neural nodes
neurotransmitters

72. Which word best describes the hypothalamus?
Chapter 33
Nervous System
Standardized Test Practice
Which word best describes the
hypothalamus?
processor
reflexor
regulator
transmitter

73. What part of the brain is highly developed
Chapter 33
Nervous System
Standardized Test Practice
What part of the brain is highly developed
in animals that have finely tuned balance
and complex coordination?
cerebellum
medulla
thalamus
temporal lobe

74. How do the sympathetic and parasympathetic
Chapter 33
Nervous System
Standardized Test Practice
How do the sympathetic and parasympathetic
nervous systems act together?
They send and receive neurotransmitters.
They send opposing signals to the same
organs.
They balance voluntary and involuntary
responses.
They receive the same impulses from
different receptors.

75. Why is this receptor located closest to the surface of the skin?
Chapter 33
Nervous System
Standardized Test Practice
Why is this receptor
located closest to the
surface of the skin?

76. It detects heavy pressure. It detects light touch.
Chapter 33
Nervous System
Standardized Test Practice
It detects cold.
It detects heat.
It detects heavy pressure.
It detects light touch.

77. What substances in the body are most
Chapter 33
Nervous System
Standardized Test Practice
What substances in the body are most
closely associated with a drug’s influence
on the nervous system?
endorphins
Na+ and K+ ions
neurotransmitters
proteins

78. Where in the nerve pathway do drugs have their primary effect?
Chapter 33
Nervous System
Standardized Test Practice
Where in the nerve pathway do drugs
have their primary effect?
axons
dendrites
synapses
myelin sheaths

79. Which step is blocked by cocaine?
Chapter 33
Nervous System
Standardized Test Practice
Which step is blocked by cocaine?

80. Glencoe Biology Transparencies
Chapter 33
Nervous System
Glencoe Biology Transparencies

81. Chapter 33
Nervous System
Image Bank

82. Section 1 Vocabulary neuron dendrite cell body axon reflex arc
Chapter 33
Nervous System
Vocabulary
Section 1
neuron
dendrite
cell body
axon
reflex arc
action potential
threshold
node
synapse
neurotransmitter

83. Section 2 Vocabulary central nervous system peripheral nervous system
Chapter 33
Nervous System
Vocabulary
Section 2
central nervous system
peripheral nervous system
cerebrum
medulla oblongata
pons
hypothalamus
somatic nervous system
autonomic nervous system
sympathetic nervous system
parasympathetic nervous system

84. Section 3 Vocabulary taste bud lens retina rods cochlea
Chapter 33
Nervous System
Vocabulary
Section 3
taste bud
lens
retina
rods
cochlea
semicircular canal

85. Section 4 Vocabulary drug dopamine stimulant depressant tolerance
Chapter 33
Nervous System
Vocabulary
Section 4
drug
dopamine
stimulant
depressant
tolerance
addiction

86. Visualizing Action Potential Impulse Movement
Chapter 33
Nervous System
Animation
Visualizing Action Potential
Impulse Movement