MUSCLE PHYSIOLOGY

Detailed explanation-1: -As a neurotransmitter binds, these ion channels open, and Na+ ions cross the membrane into the muscle cell. This reduces the voltage difference between the inside and outside of the cell, which is called depolarization.

Detailed explanation-2: -Sodium ions enter the muscle fiber, and an action potential rapidly spreads (or “fires”) along the entire membrane to initiate excitation-contraction coupling.

Detailed explanation-3: -Answer and Explanation: The correct answer is (b): Depolarization occurs when sodium ions enter into the muscle fiber cell causing the membrane potential to move towards +30 mV. Cholinergic receptors embedded in sarcolemma are ligand-gated sodium channels that open when they bind acetylcholine.

Detailed explanation-4: -In neurons, the rapid rise in potential, depolarization, is an all-or-nothing event that is initiated by the opening of sodium ion channels within the plasma membrane. The subsequent return to resting potential, repolarization, is mediated by the opening of potassium ion channels.