Describe how actin and myosin work together during muscle contraction

Question

What will be an ideal response?

Answer 1

When an action potential arrives at a muscle cell, calcium ions are released from the muscle cell's endoplasmic reticulum. Calcium ions allow a series of pivoting heads on the myosin fibers to attach to actin. The myosin heads attach and pivot, pulling on actin. Each pull shortens the length of the sarcomere a tiny bit—about 10 nanometers—and, consequently, the length of the muscle as a whole. After pulling, the myosin heads release, recock, reattach, and pull again. This cycle repeats until the signal to contract ends or until the muscle has fully contracted. Muscle contractions require energy. ATP is required for the myosin heads to release actin, an essential step in the contraction cycle.