MUSCLE PHYSIOLOGY

Detailed explanation-1: -(2) Calcium binds to troponin C, which induces a conformational change in the troponin complex. This causes tropomyosin to move deeper into the actin groove, revealing the myosin-binding sites. (B) Cross-bridge cycle in striated muscle.

Detailed explanation-2: -Regulation of Troponin and Tropomyosin If present, calcium ions bind to troponin, causing conformational changes in troponin that allow tropomyosin to move away from the myosin-binding sites on actin.

Detailed explanation-3: -The sarcoplasmic reticulum releases stores of calcium, which bind to troponin. This binding causes a conformational change in troponin that causes it to shift the position of the attached tropomyosin to uncover binding sites on actin. Myosin is then able to bind and contraction can occur.

Detailed explanation-4: -Each heartbeat is triggered by a pulse of intracellular calcium ions which bind to troponin on the actin-containing thin filaments of heart muscle cells, initiating a change in filament structure that allows myosin to bind and generate force.

Detailed explanation-5: -When calcium binds to troponin, the troponin changes shape, removing tropomyosin from the binding sites. The sarcoplasmic reticulum stores calcium ions, which it releases when a muscle cell is stimulated; the calcium ions then enable the cross-bridge muscle contraction cycle.