1) The olfactory receptor neurons in frogs resemble those of mammals, in that they express olfactory receptors that are coupled to a G protein. When the G protein is activated, it activates an adenylyl cyclase to produce cAMP, which then opens cyclic-AMP gated cation channels in the plasma membrane. The opening of these channels depolarizes the membrane, leading to the production of an action potential. Your friend is interested in why neurons stop responding to an odor after prolonged exposure to it, a process called adaptation. He has conducted experiments examining the depolarization of the olfactory receptor neuron, the binding of odorant to the receptor, the activation of the G protein, the levels of CAMP in the cell, and the phosphorylation of adenylyl cyclase. His results are summarized in Table 1. depolarization of neuron? odorant binding to receptor? activation of the G protein? CAMP levels in the cell? adenylyl cyclase phosphorylation? no odor no no no low no Table 1 brief exposure to odor yes yes yes high no after prolonged exposure to odor no yes yes low yes From these results, what step in the odor transduction pathway is altered to elicit adaptation? Propose a possible molecular mechanism to explain why olfactory neurons no longer respond to an odor after prolonged exposure to it.

Human Physiology: From Cells to Systems (MindTap Course List)
9th Edition
ISBN:9781285866932
Author:Lauralee Sherwood
Publisher:Lauralee Sherwood
Chapter4: Principles Of Neural And Hormonal Communication
Section: Chapter Questions
Problem 15RE
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1) The olfactory receptor neurons in frogs resemble those of mammals, in that
they express olfactory receptors that are coupled to a G protein. When the G
protein is activated, it activates an adenylyl cyclase to produce cAMP, which then
opens cyclic-AMP gated cation channels in the plasma membrane. The opening of
these channels depolarizes the membrane, leading to the production of an action
potential. Your friend is interested in why neurons stop responding to an odor
after prolonged exposure to it, a process called adaptation. He has conducted
experiments examining the depolarization of the olfactory receptor neuron, the
binding of odorant to the receptor, the activation of the G protein, the levels of
CAMP in the cell, and the phosphorylation of adenylyl cyclase. His results are
summarized in Table 1.
depolarization of neuron?
odorant binding to receptor?
activation of the G protein?
CAMP levels in the cell?
adenylyl cyclase phosphorylation?
no odor
no
no
no
low
no
Table 1
brief exposure
to odor
yes
yes
yes
high
no
after prolonged
exposure to odor
no
yes
yes
low
yes
From these results, what step in the odor transduction pathway is altered to elicit
adaptation? Propose a possible molecular mechanism to explain why olfactory neurons
no longer respond to an odor after prolonged exposure to it.
Transcribed Image Text:1) The olfactory receptor neurons in frogs resemble those of mammals, in that they express olfactory receptors that are coupled to a G protein. When the G protein is activated, it activates an adenylyl cyclase to produce cAMP, which then opens cyclic-AMP gated cation channels in the plasma membrane. The opening of these channels depolarizes the membrane, leading to the production of an action potential. Your friend is interested in why neurons stop responding to an odor after prolonged exposure to it, a process called adaptation. He has conducted experiments examining the depolarization of the olfactory receptor neuron, the binding of odorant to the receptor, the activation of the G protein, the levels of CAMP in the cell, and the phosphorylation of adenylyl cyclase. His results are summarized in Table 1. depolarization of neuron? odorant binding to receptor? activation of the G protein? CAMP levels in the cell? adenylyl cyclase phosphorylation? no odor no no no low no Table 1 brief exposure to odor yes yes yes high no after prolonged exposure to odor no yes yes low yes From these results, what step in the odor transduction pathway is altered to elicit adaptation? Propose a possible molecular mechanism to explain why olfactory neurons no longer respond to an odor after prolonged exposure to it.
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