Chapter 12, Problem 8RA

Electrical excitation of a muscle fiber most directly causes

$\begin{array}{l}\text{a}\text{. movement of tropomyosin}\text{.}\hfill \\ \text{b}\text{. attachment of the cross bridges to actin}\text{.}\hfill \\ \text{c}{\text{. release of Ca}}^{\text{2+}}\text{ from the sarcoplasmic reticulum}\text{.}\hfill \\ \text{d}\text{. splitting of ATP}\text{.}\hfill \end{array}$