Question

Acetylcholine binding to AChR directly leads to which of the following effects?

A. Influx of Na+
B. Release of Ca2+ from the sarcoplasmic reticulum
C. Influx of Cl-
D. Efflux of K+

Answer 1

The direct effect of acetylcholine binding to ACh receptors on the muscle cell's sarcolemma is the influx of Na+ ions, which depolarizes the membrane and initiates an action potential.

Step-by-step explanation:

When acetylcholine (ACh) binds to acetylcholine receptors (AChR) on the muscle cell's sarcolemma, it directly leads to the influx of Na+ through these ion channels, which is crucial for initiating an action potential. This action potential is necessary for muscle contraction. The binding of ACh to AChR triggers the opening of sodium ion channels, allowing Na+ ions to cross the membrane into the muscle cell, leading to depolarization of the membrane. Unlike the release of Ca2+ from the sarcoplasmic reticulum, the influx of Na+ is a direct result of ACh binding to AChR, not a subsequent intracellular event.