PHYL 1010X Lecture Notes - Lecture 1: Glycolysis, Motor Unit, Myocyte
31 May 2016
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The length of the muscle determines the rate at which ca2+ is pumped back into the sr (sarcoplasmic reticulum). The length of the muscle determines the number of cross-bridges that can be formed between myosin and actin. The length of the muscle determines how many myosin binding sites on actin filaments are obstructed by tropomyosin. Different muscle fiber types will fatigue at different rates. If you want to achieve a maximal muscle contraction, you need to recruit the motor units with the fastest fatigue rate last. Identify the order (first to last) that motor unit types are recruited to achieve a maximal contraction: fast-twitch glycolytic muscle fibers, fast-twitch oxidative-glycolytic muscle fibers, slow-twitch oxidative muscle fibers. Spatial summation involves the recruitment of multiple motor units. A motor unit refers only to the active muscle fibers. A motor unit is a single muscle fiber and all the motor neurons that innervate it.
