The event(s) that induce contraction of a muscle fiber are the
A) entry of calcium ions into the cytoplasm of the muscle fiber.
B) entry of chloride ions into the cytoplasm of the muscle fiber.
C) release of acetylcholine onto the postsynaptic membrane.
D) separation of the actin and myosin filaments.
E) movement of potassium ions into the muscle fiber.

Question

Quizplus · Accepted Answer

The entry of calcium ions into the cytoplasm of the muscle fiber is the event that induces contraction of a muscle fiber. Calcium ions bind to the protein complex troponin, which causes a conformational change in tropomyosin, uncovering the active sites on the actin filament for the myosin heads to bind and initiate muscle contraction.

The Event(s) That Induce Contraction of a Muscle Fiber Are