Chapter15 - Key 197. Fast twitch muscles *a. show little facilitation and are often used phasically. b. show considerable facilitation and are often used phasically. c. show little facilitation and are often used tonically. d. show considerable facilitation and are often used tonically. 198. Which of the following is characteristic of vertebrate "fast twitch" muscle fibers? a. They are the predominant fiber type in tonic-type muscles. b. They often show considerable facilitation. c. They are fatigue resistant. *d. They usually produce action potentials. 199. Slow twitch muscle in a vertebrate a. has a relatively weak contraction. b. shows considerable facilitation. c. is often tonic in action. *d. is all of the above. 200. Which of the following is characteristic of invertebrate "slow twitch" muscle fibers? a. They usually produce action potentials. b. They show little facilitation. c. They are the predominant fiber type in muscles used mainly in phasic-type actions. *d. They are fatigue resistant. 201. Slow twitch muscle usually shows a. strong contraction. *b. considerable facilitation. c. large, overshooting electrical responses. d. low resistance to fatigue. 202. The most simple innervation of a mammalian muscle will probably be *a. uniterminal, unineuronal. b. polyterminal, unineuronal. c. uniterminal, polyneuronal. d. polyterminal, polyneuronal. 203. The innervation of mammalian fast-twitch muscle is usually *a. uniterminal, unineuronal. b. polyterminal, unineuronal. c. uniterminal, polyneuronal. d. polyterminal, polyneuronal. 204. The most complex innervation of cat muscle in an appendage will probably be *a. uniterminal, unineuronal. b. polyterminal, polyneuronal. c. uniterminal, polyneuronal. d. polyterminal, unineuronal. 205. Fast twitch muscle fibers in vertebrate animals tend to be innervated in a ______ fashion. a. polyneuronal, uniterminal b. polyneuronal, polyterminal *c. unineuronal, uniterminal d. unineuronal, polyterminal 206. Partly because arthropod muscle cannot conduct action potentials, the SIMPLEST innervation of this muscle is a. uniterminal, unineuronal. *b. polyterminal, unineuronal. c. uniterminal, polyneuronal. d. polyterminal, polyneuronal. 207. The most complex innervation of insect muscle in an appendage will probably be a. uniterminal, unineuronal. b. polyterminal, unineuronal. c. uniterminal, polyneuronal. *d. polyterminal, polyneuronal. 208. One would expect to find a muscle fiber that does not conduct action potentials to have polyterminal innervation because a. the presence of more than one motor neuron innervating a muscle increases the flexibility with which the muscle can be used. b. only muscle fibers that cannot generate APs could distinguish between the synaptic action of different motor neurons. c. multiple epps interfere with the generation of APs. *d. multiple synapses would ensure that all parts of the muscle fiber membrane were adequately depolarized so that effective contraction could occur. 209. In a human biceps muscle, each muscle fiber is innervated by a. a different axon. b. the same axon. c. several different axons. *d. an axon that also innervates some other (but not all) muscle fibers. 210. A motor unit is a. a group of muscles that work together. b. two groups of muscles that work in opposition to each other. *c. all the muscle fibers in a muscle innervated by a single motor neuron. d. all the muscles in a limb innervated by a single nerve. 211. A motor unit is a motor neuron and a. the muscle it innervates. b. all the other motor neurons with which it is normally active. *c. all the muscle fibers it innervates. d. the parts of the muscle that functionally act as a unit during some movement. 212. Suppose a vertebrate muscle has 1,000 muscle fibers and the nerve innervating the muscle contains 100 motor neurons, each motor neuron innervating 10 muscle fibers with no overlap. The number of motor units in this muscle is a. 1. b. 10. *c. 100. d. 1,000. 213. Muscles with few motor units, and both polyterminal and polyneuronal innervation, are characteristic of a. mammals mainly. b. most vertebrates. c. insects mainly. *d. most invertebrates. 214. "Control by recruitment" in a muscle refers to a. regulation of tension by variation in the frequency of firing of individual motor units. b. the use of the size principle to control force. *c. regulation of tension by variation in the number of motor units that are active. d. the use of a matching of muscle and nerve properties to control muscle force. 215. Recruitment, a means of increasing muscle force, works through a. an increase in the number of vesicles of acetylcholine released by the motor neuron. b. activity in additional gamma motor neurons to boost the action of the alpha motor neurons. c. an increase of rate of firing in the motor neuron to cause more muscle fibers in each motor unit to be active. *d. activity in additional alpha motor neurons, thus increasing the number of active motor units contributing to the force. 216. Increase of tension in a cat's muscle is accomplished by a. increasing the frequency of firing of all the motor units. *b. recruitment of additional motor units as higher tensions are required. c. increasing the frequency of firing of only the strongest motor units. d. active control over the muscle spindle. 217. Tension in large muscles in vertebrates is controlled primarily by controlling the *a. number of active motor units. b. frequency of firing of motor units. c. firing of the large motor neurons first, followed by the small ones. d. amount of transmitter released by each action potential, through facilitation. 218. The size principle of muscle activation states a. the biggest muscles are used first. b. the smallest muscles are used first. *c. the smallest motor neurons are excited first. d. the largest motor neurons are excited first. 219. Operation of the size principle during the contraction of a human muscle will result in *a. an orderly recruitment of motor units as tension requirements increase, with some units always being activated before others. b. a recruitment of large motor units (those with the largest numbers of muscle fibers) before small ones. c. a sharing of load (during a maintained, constant contraction) between large and small motor units. d. a recruitment of motor units with large motor neurons before those with small ones. 220. In a group of motor neurons of different sizes, those with large diameter axons and somata are relatively *a. difficult to excite, and conduct APs rapidly. b. easy to excite, and conduct APs slowly. c. difficult to excite, and conduct APs slowly. d. easy to excite, and conduct APs rapidly. 221. The matching of the properties of muscle fibers to the firing characteristics of the motor neurons that innervate them means that a motor neuron that tends to fire in short, high frequency bursts will tend to innervate *a. fast twitch muscle fibers. b. slow twitch muscle fibers. c. all the fibers in a mixed muscle. d. none of the above. 222. Suppose a vertebrate muscle has 500 muscle fibers, the nerve innervating the muscle contains 50 motor neurons, and each motor neuron innervates 10 muscle fibers with no overlap. The number of motor units in this muscle is a. 10. *b. 50. c. 500. d. unknown. You can't tell from the information given. 223. Suppose an invertebrate muscle has 50 muscle fibers, the nerve innervating the muscle contains 5 motor neurons, and each motor neuron innervates 30 muscle fibers. The number of motor units in this muscle is a. 50. b. 30. *c. 5. d. unknown. It depends on the number of motor neurons that innervate each muscle fiber. 224. In vertebrates, the cell bodies of the alpha and gamma motor neurons are found in the a. dorsal root ganglion. *b. ventral gray matter of the spinal cord. c. dorsal gray matter of the spinal cord. d. ventral root ganglion.