Chapter 20 - Answer Key 34. The primary characteristic distinguishing a servomechanism is the presence of a(n) a. comparator. *b. closed (feedback) loop. c. open loop with feed forward. d. effector. 35. If you consider the vertebrate muscle spindle organ as a servomechanism, the sensor is the a. alpha motor neurons. b. extrafusal muscle fibers. c. gamma motor neurons. *d. mechanoreceptors in the spindle. 36. A good example of open loop control is a. eye movements in response to slow head movements (optokinetic reflex). *b. eye movements in response to fast head movements (vestibulo-ocular reflex). c. body temperature regulation. d. regulation of muscle tension and length. 37. The control of head position by the vestibular system can be considered a servomechanism because *a. information about head position is fed back to the motor neurons controlling the neck muscles, which in turn control the position of the head. b. information about head position is fed forward to the motor neurons controlling the neck muscles, which are then influenced by the semicircular canals. c. the output of the motor neurons controlling the neck muscles is fed back to the semicircular canals to influence the position of the head. d. the neck motor neurons are influenced by a "set point" that originates elsewhere in the central nervous system. 38. An electric fish encountering another electric fish emitting a slightly higher frequency than its own will a. ignore the other fish. b. raise its own frequency above the other fish's. *c. lower its own frequency further below the other fish's. d. jam the other fish's frequency so the other fish avoids the first. 39. A good example of neural computation, the nervous system acting to "compute" one or more parameters, is a. detection by bats of the doppler shift of an echo (to determine relative velocity of the object). b. the location of a sound source by the barn owl. c. detection by an electric fish of the frequency of a neighbor fish's EOD so it can shift its own EOD in the appropriate direction. *d. all of the above. 40. A weakly electric fish needs two main items of information about EODs in order to know whether to shift the frequency of its own EOD up or down when it detects the EOD of a neighboring fish. These two items are a. the amplitude of its own EOD and the amplitude of the EOD of the neighbor fish. *b. the amplitude of the combined EOD signal of both fish and the timing of the combined EOD relative to its own EOD. c. the frequency of the neighbor fish's EOD. d. the precise location of the neighbor fish's EOD.