The arrival of an action potential causes
A) calcium to enter the muscle fiber.
B) calcium to be released by internal organelles.
C) acetylcholine to enter the muscle fiber.
D) acetylcholine to be released by internal organelles.

Question

Quizplus · Accepted Answer

The arrival of an action potential causes calcium to be released by internal organelles called the sarcoplasmic reticulum. This calcium then binds to the protein troponin, initiating the sliding of actin and myosin filaments and ultimately leading to muscle contraction. Acetylcholine is involved in the communication between motor neurons and muscle fibers, but it does not directly cause the release of calcium.

The Arrival of an Action Potential Causes