After acetylcholinesterase acts, the synaptic terminal
A) reabsorbs the acetylcholine.
B) reabsorbs the acetate.
C) reabsorbs the choline.
D) reabsorbs axoplasm.
E) pinches off and a new terminal grows.
The correct answer and explanation is :
The correct answer is:
C) reabsorbs the choline.
Explanation:
Acetylcholinesterase (AChE) is an enzyme that plays a crucial role in terminating neurotransmission at cholinergic synapses. It does this by breaking down acetylcholine (ACh), a neurotransmitter that facilitates communication between neurons and muscle cells or between neurons in the central and peripheral nervous systems.
When an action potential reaches the synaptic terminal of a neuron, acetylcholine is released into the synaptic cleft. It binds to receptors on the postsynaptic membrane, leading to signal transmission. However, to prevent continuous stimulation, acetylcholinesterase rapidly hydrolyzes acetylcholine into two components: choline and acetate.
- Choline is reabsorbed by the presynaptic neuron through a high-affinity choline transporter. This process is crucial because neurons rely on choline to synthesize new acetylcholine using the enzyme choline acetyltransferase. This ensures a steady supply of the neurotransmitter for future signaling.
- Acetate, on the other hand, diffuses away from the synapse and is typically taken up by surrounding glial cells or metabolized elsewhere in the body.
The reabsorption of choline is an essential part of the cholinergic cycle, as neurons cannot efficiently produce choline de novo and must recycle it. If choline reuptake were blocked or impaired, acetylcholine synthesis would be reduced, leading to weakened synaptic transmission.
This process is especially important in neuromuscular junctions, where acetylcholine is critical for muscle contraction. Dysfunction in this system can lead to conditions such as myasthenia gravis, in which acetylcholine signaling is impaired, resulting in muscle weakness.
Thus, the correct answer is C) reabsorbs the choline.