Question

1. As a Nursing student in Advanced Human Anatomy, you were ableto observe a total hip replacement. While the O.R. personnel whereprepping the patient for the surgical procedure, theanesthesiologist assumed (rightly so!) that you had some physiologybackground. As such, she launched into the following proceduralexplanation: The patient will need to be intubated, therefore hewill be given a single dose of the neuromuscular blocking agent,succinylcholine to provide muscular relaxation during the surgeryand to facilitate the insertion of the endotracheal tube. Theanesthesiologist asked you the following:

a) Beginning with depolarization at the neuromuscular junction,describe the normal sequence of events which lead to musclecontraction. (10)

b) What prevents acetylcholine (ACh) from accumulating in theneuromuscular junction and causing a sustained contraction in anormal individual? (3)

c) Succinylcholine acts as a depolarizing agent that preventsrepolarization of the nerve. Therefore, no further ACh is releaseduntil the drug is cleared. Name another site within theneuromuscular junction that might be affected to prevent musclecontraction. (Hint: curare acts by this mechanism) (2)