Which step describes the release of acetylcholine from the presynaptic nerve?

Which step describes the release of acetylcholine from the presynaptic nerve?

• A. Vesicles fuse with membrane and release ACh from presynaptic nerve
• B. ACh travels the synaptic cleft and binds to a receptor on the postsynaptic nerve
• C. ACh is hydrolyzed by acetylcholinesterase
• D. Choline transported into nerve

Answer: (A)

The release of acetylcholine from the presynaptic nerve occurs by exocytosis of acetylcholine-containing vesicles. When an action potential reaches the nerve terminal, Ca2+ enters through voltage-gated channels and triggers fusion of these vesicles with the presynaptic membrane via SNARE proteins, releasing ACh into the synaptic cleft. This release is the key step that gets the transmitter into the space where it can influence the postsynaptic cell. After release, ACh diffuses across the cleft to bind receptors on the postsynaptic membrane, acetylcholinesterase then hydrolyzes ACh to terminate the signal, and choline is transported back into the nerve for reuse in making more acetylcholine.

The release of acetylcholine from the presynaptic nerve occurs by exocytosis of acetylcholine-containing vesicles. When an action potential reaches the nerve terminal, Ca2+ enters through voltage-gated channels and triggers fusion of these vesicles with the presynaptic membrane via SNARE proteins, releasing ACh into the synaptic cleft. This release is the key step that gets the transmitter into the space where it can influence the postsynaptic cell. After release, ACh diffuses across the cleft to bind receptors on the postsynaptic membrane, acetylcholinesterase then hydrolyzes ACh to terminate the signal, and choline is transported back into the nerve for reuse in making more acetylcholine.