Calcium that is needed to activate cross-bridging in smooth muscle mainly comes from
A)endoplasmic reticulum.
B)extracellular fluid.
C)intracellular fluid.
D)dense bodies.

Question

Quizplus · Accepted Answer

Calcium needed to activate cross-bridging in smooth muscle mainly comes from the extracellular fluid. This calcium enters the cell through calcium channels in the plasma membrane. While the endoplasmic reticulum and intracellular fluid do play a role in calcium regulation, they do not provide the majority of the calcium needed for smooth muscle contraction. Dense bodies are structures that anchor actin filaments in smooth muscle cells and do not play a direct role in calcium regulation.

Calcium That Is Needed to Activate Cross-Bridging in Smooth Muscle