pset+3+rationales

pset+3+rationales - Part 1 1) C The visual, gustatory and...

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Part 1 1) C The visual, gustatory and olfactory systems all use a combinatorial code to interpret an image, taste or smell in the brain. All of these systems react to stimuli via their 7-pass transmembrane proteins such as G-proteins or opsin. While taste and smell senses rely on an initial depolarization event in response to stimuli, photoreceptors hyperpolarize in response to light. In the olfactory system, each receptor can only respond to a very limited family of odorant molecules. 2) E When someone smells something they may associate it with a memory or emotion because signals may travel to their hippocampus and limbic systems. Each cell that contains the receptors for a particular odorant will project onto the same glomerulus in the olfactory bulb. When an odorant binds to a G-protein linked receptor, a signal cascade allows positive ions to flow into the cell and cause a depolarization. When this occurs, olfactory cells are capable of sending an action potential. 3) C Taste buds are regenerated very often, but your sense of taste does not change because your tongue retains a fairly constant distribution of receptors. When you ingest salt, sodium ions flow into taste cells, and when you inject something sour, H+ ions affects taste cell receptors (often by closing K+ channels) – both of these send messages to the brain by causing a change in the cell’s voltage. Each taste cell is capable of responding to a variety of taste stimuli, but it is maximally responsive to one taste. Contrary to previous beliefs, taste cells are not localized on tongue
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pset+3+rationales - Part 1 1) C The visual, gustatory and...

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