Question

Calcium re-enters the terminal cisternae during (the) phase(s) of the muscle twitch.

a) relaxation
b) latency
c) both the latency and relaxation
d) both the latency and contraction
e) contractioncalcium re-enters

Answer 1

Calcium re-enters the terminal cisternae during the relaxation phase of a muscle twitch, as calcium ions are transported back into the sarcoplasmic reticulum.

Step-by-step explanation:

Calcium re-enters the terminal cisternae of the sarcoplasmic reticulum during the relaxation phase of a muscle twitch. When the muscle is at rest, calcium ions are transported back into the sarcoplasmic reticulum, allowing the muscle to relax.

During the relaxation phase, tension decreases as calcium ions are actively transported into the sarcoplasmic reticulum, aiding in the cessation of muscle contraction. Conversely, during the latent period, an action potential merely propagates along the sarcolemma, leading to the subsequent contraction phase, where calcium ions diffuse out of the sarcoplasmic reticulum and into the sarcoplasm to initiate muscle contraction.