Question

Which of the following best describes the events that link the action potential of the sarcolemma to the action of the myofilament contraction?

A) The activation of T-tubules by calcium ions
B) The release of acetylcholine from motor neurons
C) The sliding of myosin and actin filaments past each other
D) The interaction between troponin, tropomyosin, and calcium ions

Answer 1

The interaction between troponin, tropomyosin, and calcium ions best describes the link between the action potential of the sarcolemma and myofilament contraction, as calcium released from the SR binds to troponin causing tropomyosin to unveil binding sites on actin for myosin attachment.

Step-by-step explanation:

The event that best describes the link between the action potential of the sarcolemma and the action of myofilament contraction is D) The interaction between troponin, tropomyosin, and calcium ions. When an action potential travels down the T-tubule, it triggers the release of calcium ions from the sarcoplasmic reticulum (SR). These calcium ions then bind to troponin, causing a conformational change that moves tropomyosin away from the binding sites on the actin filaments. This exposure allows myosin heads to bind to actin, forming cross-bridges that, powered by ATP, slide the thin filaments past the thick filaments within the sarcomeres, leading to muscle contraction.