A Key Difference in the Mechanism of Excitation-Contraction Coupling Between $\left[\mathrm{Ca}^{2+}\right]$

Multiple Choice

A key difference in the mechanism of excitation-contraction coupling between the muscle of the pharynx and the muscle of the wall of the small intestine is that

A) slow waves are present in the pharynx, but not in the small intestine
B) adenosine triphosphate (ATP) is used for contraction in the pharynx, but not in the small intestine
C) intracellular $\left[\mathrm{Ca}^{2+}\right]$ is increased after excitation in the pharynx, but not in the small intestine
D) action potentials depolarize the muscle of the small intestine, but not of the pharynx
E) $\mathrm{Ca}^{2+}$ binds to troponin $\mathrm{C}$ in the pharynx, but not in the small intestine, to initiate contraction