Nmj Chapter 6 Test With Solution

NMJ CHA PTER 6 TES T WITH SOLUT ION Motor unit - ANSWER spinal motor neuron and ALL the muscle fibers innervated by that single neuron all contract SIMULTANEOUSLY neuromuscular junction - ANSWER site at which the motor nerve terminal meets a muscle fiber efferent nerve terminal evokes a contraction of the muscle via an end plate potential end plate potential - ANSWER the depolarizations of skeletal muscle fibers caused by neurotransmitters binding to the postsynaptic membrane in the neuromuscular junction EPP always reaches threshold for the production of a muscle AP what type of receptors are found at a NMJ - ANSWER nicotinic ACh how is ACh removed at the NMJ - ANSWER the enzyme acetylcholinesterase breaks it down what happens during an EPP? - ANSWER action potential into presynaptic element Ca channels open Ca influx ACh released and diffuses across cleft ACh binds nicotinic receptors nicotinic receptors open permeability to K and Na increase depolarization miniature end plate potential (MEPP) - ANSWER does NOT lead to AP/muscle contraction random vesicle (NOT associated with Ca) is released, which causes a small depolarization Denervation Hypersensitivity - ANSWER exaggerated response of cardiac and smooth muscle if autonomic nerves are severed usually only sensitive to ACh at NMJ, but after denervation the entire muscle membrane becomes sensitive to ACh how long after injury does denervation hypersensitivity begin? - ANSWER 2 weeks fibrillation - ANSWER spontaneous, regular twitching of single muscle fiber s not visible through the skin, but detected by electrophysiological testing What is curare/ alpha bungarotoxin? - ANSWER an antagonist of acetylcholine that blocks acetylcholine's receptors paralyze your muscles now used during surgery to prevent twitchi ng