Sympathetic stimulation of cardiac muscle cells produces stronger and faster contractions because proteins that pump Ca²⁺ out of the cell are inhibited, which reduces Ca²⁺ concentration in the sarcoplasm.

Question

Quizplus · Accepted Answer

Sympathetic stimulation actually increases the concentration of Ca2+ in the sarcoplasm by enhancing the influx of Ca2+ through voltage-gated Ca2+ channels and by promoting the release of Ca2+ from the sarcoplasmic reticulum. This increased Ca2+ concentration leads to stronger and faster contractions of cardiac muscle cells. The proteins that pump Ca2+ out of the cell are not inhibited but rather function to maintain the proper balance of Ca2+ concentration in the cell.

Sympathetic Stimulation of Cardiac Muscle Cells Produces Stronger and Faster