Question

What two events happen after the synaptic vesicles fuse with the membrane of the axon terminal?

A. Acetylcholine is released into the synaptic cleft, and the motor end plate is depolarized.
B. Sarcomeres contract, and the action potential is generated.
C. Calcium ions bind to receptors on the motor end plate, and the T-tubules depolarize.
D. The axon terminal repolarizes, and the motor end plate hyperpolarizes.

Answer 1

The two main events that occur after synaptic vesicles fuse with the axon terminal membrane are the release of acetylcholine into the synaptic cleft and the depolarization of the motor end plate, which generates an action potential in the muscle cell.

Step-by-step explanation:

After the synaptic vesicles fuse with the membrane of the axon terminal, two main events take place:

1. Acetylcholine is released into the synaptic cleft.
2. The motor end plate is depolarized, leading to an action potential in the muscle cell.

When an action potential reaches the axon terminal, it causes the membrane to depolarize. This depolarization triggers voltage-gated Ca²+ channels to open, allowing calcium ions to enter the cell, which leads to the fusion of synaptic vesicles with the presynaptic membrane.

The neurotransmitter acetylcholine is then released into the synaptic cleft and diffuses to bind to its receptors on the sarcolemma of the muscle fiber. Once bound, ion channels open allowing Na+ ions to cross the membrane, leading to depolarization of the motor end plate, and ultimately generating an action potential that travels along the muscle fiber.