The Action Potential is Conducted into a Skeletal Muscle Fiber

Question

The action potential is conducted into a skeletal muscle fiber by
A) motor end plates.
B) neuromuscular junctions.
C) transverse tubules.
D) triads.
E) sarcoplasmic reticulum.

Accepted Answer

The action potential is conducted into a skeletal muscle fiber by transverse tubules (T-tubules), which are invaginations of the sarcolemma (plasma membrane) that run deep into the muscle fiber. T-tubules allow for rapid transmission of the action potential throughout the muscle fiber, which triggers the release of calcium ions from the adjacent membranes of the sarcoplasmic reticulum. This ultimately leads to muscle contraction. While neuromuscular junctions (A and B), triads (D), and sarcoplasmic reticulum (E) are all involved in muscle contraction, the initial conduction of the action potential into the muscle fiber relies on the T-tubules.