K⁺ Channels in the Heart Do Not Have Binding Sites

question 35

Multiple Choice

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.

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