Question

unit 2 - challenge 2.3: the muscular syst

what is a crossbridge in the context of muscle contraction?

a.) the binding of myosin heads to actin
b.) the movement of tropomyosin
c.) the connection between two muscle fibers
d.) the release of ca²+ from the sr

Explanation:

In muscle contraction, a cross - bridge is formed when myosin heads bind to actin. Tropomyosin movement (b) is part of the regulation mechanism that allows this binding. The connection between muscle fibers (c) is not related to the cross - bridge concept. The release of \(Ca^{2+}\) from the sarcoplasmic reticulum (SR) (d) is a trigger for muscle contraction but not the cross - bridge itself.

Answer:

A. The binding of myosin heads to actin