Nervous System Review Worksheet KEY

Name: _____KEY_____
Date: ______________

Nervous System Review

1. The axon of a neuron conducts nerve impulses away from the cell body, whereas the dendrites conducts
nerve impulses toward the cell body. Neurons that conduct messages from a sense organ to the central
nervous system are called sensory, or afferent, neurons. Those neurons that conduct an impulse from the
CNS to a muscle or gland are called motor, or efferent, neurons. Muscles or glands, in this case, that
respond to a nerve impulse are termed effectors. Neurons within the CNS that transmit impulses between
sensory and motor neurons are called interneurons.

2. What is a nerve fiber? composed of dendrites and/or axons of neurons.

3. Schwann cells in the peripheral nervous system will wrap around an axon and lay down an insulator
called myelin that gives nerve fibers a white, glistening appearance. Gaps where myelin is not present on
the nerve fiber are called nodes of Ranvier. These gaps allow the speed of nerve impulse conduction, called
saltatory conduction, to be increased.

4. When an axon is not conducting an impulse, the membrane potential is equal to about
-65 mV, with the inside of the neuron being negative compared to the outside. This polarity is maintained
by the sodium potassium pump in which sodium ions are pumped outside (outside/inside) the axon, and
potassium ions are pumped into the axon. Another name for the nerve impulse is the action potential which
forms when the axon is stimulated. When the sodium gates open, Na+ flow into the axon, causing the
action potential to swing up to +40 mV and the membrane to become depolarized. Now the K+ gates
open, K+ flow out (out/into) the axon, and the oscilloscope records a repolarization.

5. Label the following diagram of the reflex arc and spinal cord.
a. effector

b. axon of motor neuron
c. interneurons

d. dendrite of sensory neuron
e. receptor

f. dorsal root ganglion
g. white matter

h. gray matter of dorsal horn
i. grey matter of ventral horn

j. central canal g.—— f.___

6. In the above diagram of a spinal reflex arc, a stimulus is received by a receptor, such as the skin, which
initiates a nerve impulse in the sensory neuron. This neuron conducts the impulse to the gray matter of the
spinal cord. At this site, a second neuron, called the interneuron, conducts the impulse to the motor neuron,

Mrs. Kusec Biology 12

whose cell body lies in the ventral horn of the gray matter. This neuron, in turn, innervates an effector,
usually a muscle or gland.
7. Place each of the following statements in proper sequence by using the numbers 1-9 to describe the
transmission of a nerve impulse across a synapse.
6 a. neurotransmitter diffuses across cleft
1 b. nerve impulse travels to presynaptic membrane
4 c. microfilaments pull synaptic vesicle to presynaptic membrane
3 d. Ca++ interact with actin filaments
5 e. synaptic vesicles fuse with presynaptic membrane
9 f. neurotransmitter reabsorbed by presynaptic membrane or inactivated by

enzyme
2 g. presynaptic membrane becomes permeable to Ca++
8 h. neurotransmitter and receptor initiate excitation or inhibition of postsynaptic

membrane
7 i. neurotransmitter binds to receptor on postsynaptic membrane
8. The peripheral nervous system contains cranial nerves that connect to the brain and spinal nerves that
attach to the spinal cord. The PNS is subdivided into the somatic system, which serves system, which
serves the musculoskeletal system and the exterior sense organs, and the autonomic serves the internal
body organs. This last system is divided into the sympathetic and parasympathetic systems.
9. Label the following parts of the human brain.
a. medulla oblongata
b. pons
c. midbrain
d. brainstem
e. cerebrum
f. corpus callosum
g. thalamus
h. pituitary gland
i. cerebellum
j. spinal cord

Mrs. Kusec Biology 12

10. Fill in the table below to indicate the functions of the following parts of the brain.

Brain Part Function

Cerebrum consciousness, higher mental processes

Cerebellum muscle coordination, muscle tone

Thalamus central relay station for sensory impulses (except smell)

Hypothalmus homeostasis for hunger, sleep, thirst, body temperature, water balance, blood pressure

Midbrain relay station between cerebrum and spinal cord

Pons relays impulses between cerebellum and the rest of CNS

Medulla oblongata contains vital and non-vital reflex centers

Mrs. Kusec Biology 12