Muscle physiology: practice question

The best answer is B, Troponin C. Calcium binds troponin C on the thin filament, moving tropomyosin off the myosin-binding sites on actin and allowing cross-bridge cycling.

Tropomyosin is moved by troponin; it does not bind calcium itself.

Myosin light chain is phosphorylated in smooth muscle contraction, not triggered directly by calcium in skeletal muscle.

Calmodulin is the calcium-binding protein in smooth muscle, not skeletal muscle.

It tests Muscle physiology in Physiology. In smooth muscle, calcium instead binds calmodulin, which activates myosin light chain kinase.

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

For each system, sketch the key graph (pressure–volume loop, oxygen dissociation curve, nephron handling) and explain it aloud. Then use the flashcards and the other Physiology questions on this site to test what stuck.

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.