Question

Acetylcholine causes an end-plate potential by triggering the ________

a. opening of calcium channels
b. closing of sodium channels
c. closing of calcium channels
d. closing of chloride channels
e. opening of sodium channels
f. opening of chloride channels

Answer 1

Acetylcholine causes an end-plate potential by triggering the opening of sodium channels, leading to muscle cell depolarization and subsequent action potential.

Step-by-step explanation:

Acetylcholine (ACh) is a neurotransmitter released by motor neurons that, upon binding to receptors in the motor end plate, triggers the opening of sodium channels. This influx of Na+ ions across the membrane into the muscle cell creates an end-plate potential, leading to depolarization. This depolarization is the first step in generating an action potential, which spreads across the sarcolemma, initiating a cascade that results in muscle contraction.

Answer 2

e. Opening of sodium channels

Step-by-step explanation:

Skeletal muscle fibers are depolarized by the end-plate potential voltage. It is caused by the binding of neurotransmitter acetylcholine to the post synaptic membrane present in the neuromuscular junction. In the absence of a nerve impulse, the end plate membrane has a negative charge inside and a positive charge outside due to uneven distribution of ions. This makes the membrane polarized.

When acetylcholine is released by nerve terminal due to an impulse, it binds to the receptor molecules present on end plate. As a result, sodium channels are opened which leads to influx of sodium ions in the muscle cell. Now the membrane gets slightly depolarized. Slowly acetylcholine is degraded by an enzyme closing the channels and again polarizing the membrane.