Question

Membranous channel extending inward from muscle fiber membrane

Answer 1

The T-tubule is the membranous channel that extends inward from the muscle fiber membrane, allowing the action potential to trigger the release of calcium ions from the Sarcoplasmic Reticulum, which initiates muscle contraction.

Step-by-step explanation:

The membranous channel extending inward from the muscle fiber membrane that you are asking about is known as the T-tubule (transverse tubule). These are periodic invaginations of the sarcolemma that ensure the action potential can travel into the interior of the cell. When an action potential propagates along the sarcolemma, it enters the T-tubules and triggers the opening of calcium channels in the membrane of the adjacent Sarcoplasmic Reticulum (SR). This results in the diffusion of calcium ions (Ca++) into the sarcoplasm, which is key in initiating the contraction of the muscle fiber's contractile units, known as sarcomeres.

Answer 2

The correct answer is- transverse tubules.

Step-by-step explanation:

Transverse tubules are the membranous channel that extends inward from the muscle cell, these are the actually the addition or extensions of the cell membrane that invade into the center of muscles cells except smooth muscles.

The role of the transverse tubules is to generating the stimulus or signals from the sarcolemma to down in the cell. Sarcolemma are the surface of the cells in muscles.

Thus, the correct answer is - transverse tubules.