HTHSCI 1H06 Chapter Notes - Chapter 10: Neuromuscular Junction, Myocyte, Motor Unit
14 Dec 2015
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Document Summary
The total force or tension that a single muscle fiber can produce depends mainly on the rate at which nerve impulses arrive at the neuromuscular junction: the number of impulses per second is the frequency of stimulation. The total tension a whole muscle can produce depends on the number of muscle fibers that are contractingmin unison. Each skeletal muscle fiber has only a single neuromuscular junction but the axon of a somatic motor neuron branches out and forms neuromuscular junctions with many different muscle fibers. Whole muscles that control precise movements consist of many small motor units. 2msec = latent tropomyosin -> myosin heads detach from actin, and tension in the muscle fiber decreases. Three phases: during the latent period, the muscle action potential sweeps over the sarcolemma and calcium ions are released from the sarcoplasmic reticulum, the contraction period, lasts 10 100 msec. During this time, ca2+ binds to troponin, myosin-binding sites on actin are exposed, and cross-bridges form.
