Lecture 22

Lecture 22 - Muscle Mechanics 1. The Muscle Twitch...

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Muscle Mechanics 1. The Muscle Twitch contraction arising from a single electrical stimulus e.g., an action potential 3 Periods 1. Latent 2. Contraction 3. Relaxation
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1. Latent Period •2 msec or less •Action potential sweeps over the sarcolemma •Calcium ions released from the sarcoplasmic reticulum •No change in tension
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2. Contraction Period •10 - 100 msec •Calcium binds to troponin •Myosin-binding sites on actin are exposed •Crossbridges form and swivel •Peak tension develops
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3. Relaxation Period •10-100 msec •Calcium ions transported back into the sarcoplasmic reticulum •Myosin binding sites on actin are covered by tropomyosin •Myosin heads detach from actin •Tension decreases
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Time T e n s i o eye gastroc. soleus The Time Course of a Twitch varies for different muscles (‘fast twitch’ vs. ‘slow twitch’)
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Muscle Mechanics 2. Tetanus ‘summation’ over time ( Temporal Summation ) of individual twitches Tetanus (temporal summation) is a mechanism for increasing tension
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Tension Production and the Motor Unit Motor Unit: a motor neuron and all the muscle fibers (cells) it innervates
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Lecture 22 - Muscle Mechanics 1. The Muscle Twitch...

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