- As tissue fluid, CSF brings nutrients to CNS neu-
rons and removes waste products. CSF also acts as
a shock absorber to cushion the CNS.
Cranial Nerves—12 pairs of nerves that
emerge from the brain (see Fig. 8–11)
- Concerned with vision, hearing and equilibrium,
taste and smell, and many other functions. - See Table 8–4 for the functions of each pair.
The Autonomic Nervous System (ANS) (see
Fig. 8–12 and Table 8–5)
- Has two divisions: sympathetic and parasympa-
thetic; their functioning is integrated by the hypo-
thalamus. - Consists of motor neurons to visceral effectors:
smooth muscle, cardiac muscle, and glands. - An ANS pathway consists of two neurons that
synapse in a ganglion:- Preganglionic neurons—from the CNS to the
ganglia - Postganglionic neurons—from the ganglia to the
effectors - Most sympathetic ganglia are in two chains
just outside the vertebral column; parasympa-
thetic ganglia are very near or in the visceral
effectors.
- Preganglionic neurons—from the CNS to the
- Neurotransmitters: acetylcholine is released by
all preganglionic neurons and by parasympa-
thetic postganglionic neurons; the inactivator is
cholinesterase. Norepinephrine is released by most
sympathetic postganglionic neurons; the inactiva-
tor is COMT or MAO. - Sympathetic division—dominates during stress sit-
uations; responses prepare the body to meet physi-
cal demands. - Parasympathetic division—dominates in relaxed
situations to permit normal functioning.
194 The Nervous System
REVIEW QUESTIONS
- Name the divisions of the nervous system and state
the parts of each. (p. 166) - State the function of the following parts of nerve
tissue: (pp. 166–167)
a. Axon
b. Dendrites
c. Myelin sheath
d. Neurolemma
e. Microglia
f. Astrocytes - Explain the difference between: (pp. 170–171)
a. Sensory neurons and motor neurons
b. Interneurons and nerve tracts - Describe an electrical nerve impulse in terms of
charges on either side of the neuron membrane.
Describe how a nerve impulse crosses a synapse.
(pp. 168–169, 171) - With respect to the spinal cord: (p. 172)
a. Describe its location
b. State what gray matter and white matter are
made of
c. State the function of the dorsal root, ventral
root, and dorsal root ganglion
6. State the names and number of pairs of spinal
nerves. State the part of the body supplied by
the phrenic nerves, radial nerves, and sciatic nerves.
(pp. 172, 174)
7. Define reflex, and name the five parts of a reflex
arc. (pp. 172, 174)
8. Define stretch reflexes, and explain their practical
importance. Define flexor reflexes, and explain
their practical importance. (p. 175)
9. Name the part of the brain concerned with each of
the following: (pp. 176–179)
a. Regulates body temperature
b. Regulates heart rate
c. Suppresses unimportant sensations
d. Regulates respiration (two parts)
e. Regulates food intake
f. Regulates coordination of voluntary movement
g. Regulates secretions of the anterior pituitary
gland
h. Regulates coughing and sneezing
i. Regulates muscle tone
j. Regulates visual and auditory reflexes
k. Regulates blood pressure