Study Guide for Chapter 13

1.         What are the various categories (and sub-categories) of muscle?

2.         You should be familiar (and comfortable) with the following terms: flexion (& flexors), extension (& extensors), synergists (agonists), antagonists, axial, proximal (girdle),and distal.

3.         To what was Sherrington referring when he spoke of “the final common pathway?”

4.         How many pairs of spinal nerves do human beings have? Why are they called “mixed nerves?”

5.         What are upper motor neurons? What are alpha motor neurons? What makes up one motor unit? What about a motor neuron pool?

6.         How is a graded and smooth contraction accomplished from muscle fibers twitching? In other words, what is twitch summation? What is an innervation ratio? What is the basic principle of motor unit recruitment (the size principle)?

7.         Why are we able to make fine, precise movements if the load is light but not when it is heavy? (Note: this is really another way of phrasing question #6.)

8.         What are the three sources of input into alpha motor neurons?

9.         How are motor units categorized on the basis of contractile rate, fatigue-ability, and appearance?

10.       Why is “phenotype switching” an especially interesting phenomenon? What are the implications of this?

11.       What impact do variations in muscle use have on muscles and muscle fibers?

12.       You should know the structure of a muscle fiber and the steps involved in excitation, contraction, and relaxation of muscle fibers (the sliding filament model).

13.       How is proprioception accomplished by muscle spindles? What is the difference between intrafusal and extrafusal fibers? What is a gamma motor neuron? A gamma loop?

14.       What is the basic structure of a Golgi tendon organ? How is proprioception accomplished by Golgi tendon organs?

15.       What other sources of proprioception are there?

16.       Why can a patient who has had a hip replacement still tell the angle of their thigh relative to their pelvis?

17.       What role do spinal interneurons play in the execution of reflexes (inhibitory and excitatory)?