K+ channels in the heart do not have binding sites for ACh, yet parasympathetic release of ACh causes outward flux of K+ from heart cells. How does this occur?
A. ACh triggers release of epinephrine from the adrenal glands, which in turn causes K+ flux out of heart cells.
B. ACh binds to a G-protein coupled receptor on heart cells, and the G protein alpha subunit binds to a separate K+ channel and causes it to open.
C. Parasympathetic neurons activate sympathetic neurons, which directly cause K+ flux from heart cells.
D. ACh binds and activates a K+ pump on heart cells.
B. ACh binds to a G-protein coupled receptor on heart cells, and the G protein alpha subunit binds to a separate K+ channel and causes it to open.
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