Chapter 16 225. Recurrent inhibition is a process a. by which gamma motor neurons turn themselves off. b. by which alpha motor neurons turn themselves off. c. that does not occur in vertebrates. d. of sensory feedback onto a central pattern generator. 226. Recurrent inhibition of motor neurons in mammals occurs via a. Renshaw cells. b. Henshaw cells. c. Rorshach cells. d. Ranshow cells. 227. The negative feedback loop known as recurrent inhibition involves which of the following functional connections? a. Sensory neuron inhibition of a Renshaw cell. b. Sensory neuron excitation of a Renshaw cell. c. Motor neuron excitation of a Renshaw cell. d. Motor neuron inhibition of a Renshaw cell. 228. A negative feedback loop on motor neurons, known as recurrent inhibition, involves a. motor neuron collaterals. b. sensory neuron collaterals. c. interneuron collaterals. d. no collaterals at all. 229. The Renshaw cell a. is the interneuron involved in two-tone suppression in the inner ear. b. is a spinal interneuron which directly inhibits the motor neurons that stimulate it. c. allows visual contrast enhancement via reciprocal inhibition. d. encodes the tension of the spindle receptor organ. 230. ______ made important contributions to our knowledge of vertebrate reflexes. a. Wiersma and Ikeda b. Kuffler c. Sherrington d. Katz & Miledi 231. The "association" neuron in a reflex arc a. has its cell body in the dorsal root ganglion. b. is entirely located in the gray matter of the spinal cord. c. is entirely located in the white matter of the spinal cord. d. sends its axon out the ventral root of the spinal cord. 232. The function of an association neuron in a reflex arc is probably NOT a. to change excitation to inhibition. b. to spread the sensory signal to other parts of the nerve cord. c. to allow for more integration with other signals. d. none of the above. 233. Which of the following is a function of an association neuron in a reflex arc? a. To change excitation to inhibition. b. To spread the sensory signal to other parts of the nerve cord. c. To allow for more integration with other signals. d. All of the above. 234. The function of "association" neurons in reflexes is to a. spread information about the stimulus to the other side of the spinal cord. b. spread information about the stimulus to other levels of the spinal cord. c. change the sign of the incoming sensory signal. d. all of the above. 235. One function of interneurons in a reflex arc is to a. control the effectiveness of the sensory input on alpha motor neurons. b. suppress conscious pain perception during a reflex withdrawal from a painful stimulus. c. spread information about the stimulus to other areas of the spinal cord from the site at which they first enter. d. enhance the excitatory effect on extensor motor neurons. 236. Reciprocal inhibition in a reflex refers to a. the inhibition of extensor muscle motor neurons on the opposite side of the body. b. the inhibition of flexor motor neurons by feedback from extensor motor neurons in a single limb, and vice versa. c. the change in sign of an incoming sensory signal from positive (excitatory) to negative (inhibitory). d. the inhibition of flexor muscle motor neurons by a noxious sensory stimulus. 237. In a crossed extension reflex, the sensory afferent carrying a noxious stimulus makes excitatory synaptic contact with interneurons that a. cross over to the other side of the spinal cord to excite extensor motor neurons. b. cross over to the other side of the spinal cord to inhibit extensor motor neurons. c. synapse with inhibitory interneurons that cross over to the other side of the spinal cord and inhibit extensor motor neurons. d. synapse with flexor motor neurons, whose recurrent branches cross over to the other side of the spinal cord and excite extensor motor neurons. 238. The phrase "crossed extension reflex" refers to a reflex in which a. muscles synergistic to a major limb muscle are excited. b. muscles antagonistic to a major limb muscle are inhibited. c. extensor muscles in a limb on the other side of the body are excited. d. flexor muscles in a limb on the other side of the body are excited. 239. A noxious stimulus applied to the rear foot of a standing cat will induce it to lift that foot. As it does so, extensor muscles in the front leg on that same side of the body will increase their activity due to excitation of extensor muscle motor neurons by a. monosynaptic input from the sensory fibers carrying information about the stimulus. b. monosynaptic input from branches (collaterals) of rear-leg flexor motor neurons. c. input from interneurons excited by branches of rear-leg flexor motor neurons. d. input from interneurons excited by the sensory fibers carrying information about the stimulus. 240. One of the main problems in explaining the coordination of behavior is explaining how a. the vigor of a behavior is determined. b. a particular behavior is selected to be performed. c. the selection and timing of muscle activity is determined. d. all of the above. 241. A central pattern generator is a. a group of cells that are reciprocally inhibited. b. the source of all of an animal's behavior. c. a group of cells that controls all movements of a single appendage. d. a group of cells that is capable of generating rhythmic output while receiving only non-rhythmic input. 242. Wilson was instrumental in a. working out the function of vertebrate reflexes. b. demonstrating the existence of the central control of rhythmic behavior. c. developing the concept of a command neuron. d. establishing the functioning of vertebrate central synapses. 243. ______ provided strong evidence for the idea of the central control of rhythmic behavior. a. Sherrington b. Evarts c. Wilson d. Wiersma and Ikeda 244. Wilson knew before he started his work on locust flight that the timing of the wing movements was due to a purely central mechanism. This statement is a. false, because the idea of central control had not yet been proposed. b. false, because at that time rhythmic behaviors were thought to be controlled by peripheral timing cues. c. true, because no idea besides that of central control had been thought of. d. true, because at that time rhythmic behaviors were thought to be controlled by a central mechanism. 245. Removal of all sensory input from the wings and wing bases of a locust caused a. no effect on the frequency or amplitude of the wing beats. b. the fore wings to beat in time with the hindwings. c. an increase in the frequency but a decrease in the amplitude of the wing beats. d. a reduction in the frequency of wing beating without any significant effect on the timing of wing movements relative to one another. 246. The purpose of the experiment in which the front and hind wings of a locust were fastened together was a. to see whether the timing of front and rear wing muscles would be altered by the incorrectly timed sensory input from the front wings. b. to determine which wing pair, front or rear, was the stronger. c. to see which wing sense organs were responsible for maintaining proper timing of wing movements. d. all of the above. 247. A "fictive" behavior is one that a. does not exist in the normal, intact animal. b. is only imagined by the animal. c. an animal is "trying" to produce, but without any actual movement being generated. d. involves the animal's control of its self-generated sensory input. 248. "Fictive" behavior refers to a. the generation of a motor pattern by a nervous system without the production of any movements or muscular contractions. b. the study of neural models (networks) and their simulation by computers. c. the "emergent property" of networks of neurons that act as pattern generators. d. none of the above. 249. A neural model is a. a network of neurons with an emergent property. b. a network of neurons that can produce rhythmic motor output in the absence of any rhythmic input. c. a general statement about the conditions that will produce a particular behavior. d. a hypothetical arrangement of neurons intended to explain how a particular neural output may be generated by the CNS. 250. Wilson's model of a locust flight central pattern generator looked most like which of the following ( = inhibition; = excitation )? a. c. b. d. 251. Wilson's model of the network of neurons controlling the activity of elevator and depressor muscles of a locust wing is based primarily on a. a pacemaker cell that does not need sensory input. b. reciprocal inhibition between a pair of interneurons. c. a command neuron with rhythmic output. d. constant driving of one set of muscles, with periodic inhibition from an oscillator to produce rhythmic output. 252. A central pattern generator (CPG) is a. any network of neurons capable of producing rhythmic motor output. b. a network of neurons capable of generating alternating or rhythmic motor output in the absence of any rhythmic sensory input. c. a group of neurons showing reciprocal inhibitory connections, and capable of generating a rhythmic pattern of motor output. d. an imaginary ideal of neuronal organization that does not fit any of the other definitions above. 253. Post-inhibitory rebound is a. the recovery of the membrane potential after an IPSP. b. the effect of presynaptic inhibition on the post-synaptic membrane. c. facilitation of IPSPs. d. excitation of a neuron due to its release from inhibition. 254. Post-inhibitory rebound is the spontaneous a. generation of action potentials following release of a neuron from inhibition. b. increase in size of an action potential after inhibition. c. increased excitatory post-synaptic effects following pre-synaptic inhibition. d. spontaneous increase in post-synaptic facilitation following inhibition. 255. Post-inhibitory rebound refers to a. the recovery of the membrane potential after inhibition. b. the ionic mechanisms that help restore the potential after an IPSP. c. the change in threshold that follows any change in membrane potential. d. none of the above. 256. The excitation of a neuron due to its release from inhibition, without any excitatory input, is called a. spontaneous activity. b. post-inhibitory rebound. c. pacemaker activity. d. facilitation. 257. Post inhibitory rebound is possible in some neurons because a. depolarization such as that following the cessation of inhibition always causes generation of APs. b. pacemaker cells show a positive inward current at rest that renders them very susceptible to excitation. c. hyperpolarization lowers the threshold as well as the membrane potential, so that when the cell is released from inhibition, the membrane potential goes above threshold. d. inhibition of an inhibitory neuron is functionally the same as direct excitation. 258. In studies of crayfish and lobsters, interneurons have been found that a. seem to be coordinating neurons for swimmeret movements in different abdominal segments. b. can cause the beating of a few of the swimmerets when they are stimulated. c. cause the animal to adopt a particular posture when they are stimulated. d. do all of the above. 259. Individual pattern generators are thought to be coupled centrally by a. command neurons. b. coordinating neurons. c. intrinsic neurons. d. concentric neurons. 260. Separate, independent coordinating interneurons have been shown to be necessary for intersegmental coordination in a. cockroaches. b. crayfish. c. frogs. d. sharks.