Chapter 14 – Peripheral Nervous System
This chapter on the PNS picks up the discussion of somatic sensory and somatic
motor pathways with an exploration of the nerve pathways that lead to and from the
CNS, together comprising the PNS. Discussion opens with the 31 pairs of spinal
nerves that emerge from the spinal cord and the smaller nerves in turn emerging from
them. Next, the 12 pairs of cranial nerves and their functions are discussed. The
afferent and efferent divisions of the PNS are then introduced; the central discussion
in this chapter focuses on the efferent division, which is further divided into the somatic
motor nervous system and the autonomic efferent nervous system. Differentiations
are made between the sympathetic and parasympathetic divisions of the autonomic
nervous system.
Objectives
1.
Discuss the generalized structure or branching of a typical spinal nerve.
2.
Identify the location of the four major pairs of plexuses.
3.
Identify the cranial nerves by name and give the generalized function of each.
4.
Identify the basic principles of somatic motor pathways.
5.
List and discuss several of the somatic reflexes of clinical importance.
6.
Identify the two major subdivisions of the autonomic nervous system.
7.
Discuss the structures and function of the autonomic nervous system.
8.
Compare and specify functions of the sympathetic and parasympathetic divisions
of the autonomic nervous system.
To guide you in meeting your objectives, please answer the following questions.
Your textbook should be your primary resource. However, please feel free to
search out other resources for further clarification.
1. How many pairs of spinal nerves are connected to the spinal cord? What are the major groups of
spinal nerves and how many of each do we have? Note the “blast from the past”!
2. Describe the structure of a spinal nerve. Be sure to include the following: ventral root, dorsal
root, dorsal root ganglion, and spinal nerve rami.
3. Why are spinal nerves considered mixed nerves?
4. What is a nerve plexus?
5. What is the function of the phrenic nerves? Explain their significance in the case of a broken neck.
6. What are dermatomes? myotomes?
7. Discuss the cause, physiology, and symptoms of Herpes zoster (Shingles).
8. Identify the cranial nerves by name and give the generalized function of each.
HINT: ☺ Can't remember the names of the cranial nerves? Here is a fun mnemonic device for you:
On Old Olympus Towering Top A Famous Vocal German Viewed Some Hops!
The bold letters stand for: Olfactory, Optic, Oculomotor, Trochlear, Trigeminal, Abducens,
Facial, Vestibulocochlear, Glossopharyngeal, Vagus, Spinal accessory, Hypoglossal.
Here is a great interactive website for you to visit and practice!
http://www.can-do.com/uci/ssi2001/cranial.html
9. What are the 2 functional divisions of the PNS? What are the 2 major subdivisions of the motor
(efferent) division?
10. Answer the following with respect to somatic efferent pathways.
a. What are the major players in a somatic motor pathway?
b. How many neurons between the CNS and effector?
c. What are the effectors innervated?
d. Neurotransmitter(s)?
11. Compare & contrast somatic & autonomic reflexes.
12. What is the major function of the autonomic nervous system?
13. Answer the following with respect to autonomic efferent pathways.
a. What are the major players in an autonomic motor pathway?
b. How many neurons between the CNS and effector?
c. What are the effectors innervated?
d. Neurotransmitter(s)?
14. What are the two major subdivisions of the autonomic nervous system?
15. What are the major functions of the parasympathetic division of the autonomic nervous system?
16. What are the major functions of the sympathetic division of the autonomic nervous system?