Anatomy and Physiology Answer Key

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Unformatted text preview: stant, background sensory information to be ignored. (a) Generator potentials are localized depolarizations and are graded (of different sub-threshold magnitude). Unlike action potentials they are not self-propagating. (b) It is important that a receptor does not respond to stimuli at sub-threshold intensities as this could mean the receptor would be responding inappropriately and too often. Note: The threshold level is a stimulus intensity that is established through natural selection as appropriate in the prevailing environment and (like other biological responses) is subject to change over time. The Structure of the Eye (page 85) The Physiology of Vision (page 87) 1. Feature Rod cells Cone cells Visual pigment(s): Rhodopsin Iodopsin (no color vision) (three types) Visual acuity: Low High Overall function: Vision in dim light, high sensitivity Color vision, vision in bright light 2. (a)-(c) in any order (a) Photoreceptor cells (rods and cones) respond to light by producing generator potentials. (b) Bipolar neurons form synapses with the rods and cones and transmit the changes in membrane potential to the ganglion cells. Each cone synapses with one bipolar (=high acuity) whereas each rod synapses with many bipolar cells (=high sensitivity). (c) Ganglion cells synapse with the bipolar cells and respond with depolarization and generation of action potentials. Their axons form the optic nerve. 1. (a) Cornea: Responsible for most of the refraction (bending) of the incoming light. (b) Ciliary body: Secretes the aqueous humour which helps to maintain the shape of the eye and assists in refraction. (c) Iris: Regulates the amount of light entering the eye for vision in bright and dim light. 3. (a) Horizontal cells are interconnecting neurons that help to integrate and regulate the input from multiple photoreceptor cells. They enhance information about contrast. (b) Amacrine cells form synapses with bipolar cells and work laterally to affect output from the bipolar cells, enhancin...
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This document was uploaded on 01/28/2014.

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