BIOSC-101 Lecture Notes - Lecture 19: Troponin, Neuromuscular Junction, Myoglobin
9 Sep 2020
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Document Summary
Junction between the tip of a motor neuron and a skeletal muscle cell. A muscle contracts while actin & myosin and thus slide past each other. This shortens the sarcomere and thus the muscle but not the actin & myosin myofilaments. Shape changes tropomyosin shifts away from binding site of actin. Within a few hours after death, the muscles become stiff = rigor mortis. Muscle contraction will occur as long as atp is present. Actin & myosin gradually break down & muscle relax again after 2-3 days. A motor neuron and all the muscle cells it stimulates. 150 muscle cells in a motor unit. Twitch: single short contraction due to single pulse of stimulation. Summation: 2nd twitch builds on previous twitch due to the delivery of a 2nd pulseof stimulation right after 1st pulse of stimulation. At threshold, as stimulus frequency increases, summation occurs until tetanus is reached.
