BIOL273 Chapter Notes - Chapter 3: Myocyte, Motor Neuron, Motor Unit
11 Sep 2016
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E. g. fast twitch fibres used for playing piano, tapping finger, kicking something, whereas slow twitch fibres better for posture, walking, running etc. Motor unit: basic unit of contraction in muscle fibres, composed of a group of fibres that function together and the somatic motor neuron that controls them. When the somatic motor neuron fires an action potential, all the muscle fibres contract. But the metabolic characteristics of fibres have some plasticity/can be changed. With endurance training, fast twitch fibres can be enhanced so they"re fatigue resistant like slow twich fibres. Force can be changed by recruiting additional motor units. As stimulus increases, somatic motor neurons with highest thresholds begin to fire. Fast twitch can have more force than slow twitch, but gets tired easier. Sustained contractions require continuous action potentials. increasing the stimulus rate results in summation of contractions but if the fibre is easily fatigued summation leads to fatigue and diminished force.
