You are taking notes in a lecture, writing as fast as you can, when suddenly your hand become so stiff that you can't write any more. You pull the pencil from between your frozen fingers with your other hand, and after a few worried moments your hand is able to relax again. What happened? A) The muscles in your hand depleted their supply of ATP, and the myosin heads could not detach from actin. B) The muscles in your hand depleted their supply of acetylcholinesterase. C) The muscles in your hand depleted their supply of Ca ²⁺, and the myosin heads could not attach to actin. D) The actin and myosin filaments in your hand muscles became detached from their Z lines. E) The motor neurons stimulating your hand muscles depleted their supply of acetylcholine.

Question

Quizplus · Accepted Answer

The stiffness and inability to relax the hand muscles in this scenario is due to the depletion of ATP. ATP is necessary for the myosin heads to detach from actin filaments during muscle contraction. Without sufficient ATP, the muscles cannot relax, leading to stiffness.

You Are Taking Notes in a Lecture, Writing as Fast