An increase in intracellular calcium ion results in myocardial contraction,because calcium
A) activates membrane calcium pumps.
B) binds troponin, causing actin-binding sites to be exposed.
C) increases affinity of myosin for actin cross-bridge sites.
D) promotes ATP synthesis.

Question

Quizplus · Accepted Answer

Each troponin is composed of three subunits called troponins T,I,and C.Troponin T binds to tropomyosin,troponin I participates in the inhibitory actions of tropomyosin,and troponin C binds up to four molecules of Ca²⁺.Intracellular calcium ions do not activate membrane calcium pumps in myocardial contraction.Calcium ions do not increase the affinity of myosin for actin cross-bridge sites.Myosin cleaves to ATP to release energy for muscle contraction.

An Increase in Intracellular Calcium Ion Results in Myocardial Contraction,because