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.

Question

Quizplus · Accepted Answer

ACh binds to a G-protein coupled receptor on heart cells, activating the G protein alpha subunit, which then binds to a separate K⁺ channel and causes it to open. This allows for the outward flux of K⁺ from heart cells, despite the fact that the channels themselves do not have binding sites for ACh.

K+ Channels in the Heart Do Not Have Binding Sites

K⁺ Channels in the Heart Do Not Have Binding Sites