Cardiac muscle tissue is sensitive to changes in the concentration of which ion?

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Multiple Choice

Cardiac muscle tissue is sensitive to changes in the concentration of which ion?

Calcium ions regulate cardiac muscle contraction. When a heartbeat triggers an action potential, voltage-gated calcium channels in the T-tubules open and let Ca2+ enter the cytosol. This influx triggers a larger release of Ca2+ from the sarcoplasmic reticulum, a process called calcium-induced calcium release. The resulting rise in cytosolic Ca2+ allows calcium to bind to troponin C, moving tropomyosin away from actin’s binding sites and enabling cross-bridge cycling that contracts the muscle. Because the strength of cardiac contraction depends directly on the amount of available cytosolic Ca2+, changes in calcium concentration have a powerful influence on heart function. Sodium mainly drives electrical excitation, potassium sets the resting and repolarization phases, and chloride plays a minor role in this context.

Calcium ions regulate cardiac muscle contraction. When a heartbeat triggers an action potential, voltage-gated calcium channels in the T-tubules open and let Ca2+ enter the cytosol. This influx triggers a larger release of Ca2+ from the sarcoplasmic reticulum, a process called calcium-induced calcium release. The resulting rise in cytosolic Ca2+ allows calcium to bind to troponin C, moving tropomyosin away from actin’s binding sites and enabling cross-bridge cycling that contracts the muscle. Because the strength of cardiac contraction depends directly on the amount of available cytosolic Ca2+, changes in calcium concentration have a powerful influence on heart function. Sodium mainly drives electrical excitation, potassium sets the resting and repolarization phases, and chloride plays a minor role in this context.

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