Question

The functional role of the T tubules is to ________?

1) stabilize the G and F actin
2) enhance cellular communication during muscle contraction
3) hold cross bridges in place in a resting muscle
4) synthesize ATP to provide energy for muscle contraction

Answer 1

T-tubules are invaginations of the sarcolemma in muscle cells that carry the action potential and trigger the release of calcium ions. Actin-binding sites become available for cross-bridging with myosin heads when calcium ions bind to troponin and cause a shift in the position of tropomyosin.

Step-by-step explanation:

The T-tubules, or transverse tubules, are invaginations of the sarcolemma in muscle cells. Their role is to carry the action potential deep into the muscle fiber, allowing for the efficient and synchronous contraction of the entire muscle fiber. The T-tubules are also involved in triggering the release of calcium ions from the sarcoplasmic reticulum, which is essential for muscle contraction.

During muscle contraction, actin-binding sites become available for cross-bridging with myosin heads. This is achieved through a process called calcium-induced conformational change. When calcium ions bind to the protein complex called troponin, this causes a shift in the position of tropomyosin, exposing the binding sites on the actin filaments. As a result, myosin heads can bind to actin, forming cross-bridges and initiating muscle contraction.