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BISC 307 - Exam 2 (20071)

BISC 307 - Exam 2 (20071) - Second Exam ANSWERS BISC 307L...

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Second Exam - ANSWERS BISC 307L - General Physiology March 5, 2007 8 pts. 1. Define “parallel channels” in the context of sensory systems. Then, briefly explain how parallel channels enhance sensitivity in sensory systems. Be sure to discuss the role of spatial summation in your answer. It is not necessary to cite a specific example, but if you do, be sure that it illustrates the general principles. ANS: “Parallel channels” refers to the situation in which large numbers of similar sensory receptors are connected to the central nervous system in parallel. Parallel channels enhance sensitivity in the following way. A weak stimulus may have only a small chance of producing an action potential in any particular receptor. Since most receptors are spontaneously active, with random intervals between action potentials, an “extra” action potential, correlated in time with the stimulus, would be an ambiguous signal. If the CNS monitors many parallel channels at once, however, several “extra” action potentials, occurring simultaneously and synchronously with the stimulus, would be an unambiguous signal. The CNS averages the inputs from the parallel channels via spatial summation. 5 pts. 2. Write a number in each blank to match each term on the left with its most appropriate definition on the right. Each definition should only be used only once or not at all. ________ a. epinephrine 1. postganglionic neurons that release acetylcholine ________ b. parasympathetic 2. transmitter causing vasodilation in salivary glands ________ c. craniosacral 3. hormone released from adrenal cortex ________ d. acetylcholine 4. released during fight or flight response ________ e. adrenergic 5. binds to P1 or P2 receptors on target cells 6. type of receptor on parasympathetic target cells 7. location of parasympathetic outflow from CNS 8. type of receptor on sympathetic target cells 9. location of sympathetic outflow from CNS ANS: a-4, b-1, c-7, d-10, e-8 10. main transmitter in all autonomic ganglia 6 pts. 3. a) Define the receptive field of a sensory neuron. b) Define a topographic map (= topographic projection) in a typical brain area that processes sensory information. c) What arrangement of receptive fields leads to the formation of such topographic maps? ANS: a) The receptive field of a sensory neuron is that area of the receptive surface within which application of a stimulus affects the activity of that neuron.
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