Sympathetic stimulation of cardiac muscle cells produces stronger and faster contractions because the concentrations of Ca²⁺ in the sarcoplasm are reduced by inhibition of proteins that pump it out of the cell.

Question

Quizplus · Accepted Answer

Sympathetic stimulation increases the concentrations of Ca2+ in the sarcoplasm by promoting its release from the sarcoplasmic reticulum. This enhances the ability of contractile proteins to produce force and shorten more rapidly, resulting in stronger and faster contractions. Proteins that pump Ca2+ out of the cell are not inhibited by sympathetic stimulation, as this would lead to a toxic buildup of intracellular Ca2+ that could disrupt cellular function.

Sympathetic Stimulation of Cardiac Muscle Cells Produces Stronger and Faster