1. As a Nursing student in Advanced Human Anatomy, you were able to observe a total hip replacement. While the O.R. personnel where prepping the patient for the surgical procedure, the anesthesiologist assumed (rightly so!) that you had some physiology background. As such, she launched into the following procedural explanation: The patient will need to be intubated, therefore he will be given a single dose of the neuromuscular blocking agent, succinylcholine to provide muscular relaxation during the surgery and to facilitate the insertion of the endotracheal tube. The anesthesiologist asked you the following:

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

b) What prevents acetylcholine (ACh) from accumulating in the neuromuscular junction and causing a sustained contraction in a normal individual? (3)

c) Succinylcholine acts as a depolarizing agent that prevents repolarization of the nerve. Therefore, no further ACh is released until the drug is cleared. Name another site within the neuromuscular junction that might be affected to prevent muscle contraction. (Hint: curare acts by this mechanism) (2)