Muscle structure and Function Outline

Muscle structure and Function Outline - Muscle Structure...

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Muscle Structure and Function Outline Types of Contractions o Isometric: muscle doesn’t change with tension o Concentric: muscle shortens with tension o Eccentric: muscle lengthens with tension Skeletal muscle o Elongated cell, multiple nuclei, visible striations, voluntary Internal structure  o Fascicles--muscle cells (fibers)--myofibrils o T tubules Conduct a signal deep into myofibrils to stimulate SR to release Ca to  initiate contraction process o Myofibril Thin actin filament Thick myosin filament o Striation Dark=”a band” overlap of actin and myosin filaments Z line to z line= shorten when muscle contracts, thin actin filaments are  attached here The Neuromuscular junction (THE SIGNAL) o motor neuron stimulates a muscle cell o From spinal cord (motorneurons) innervate select muscle fibers o Basic anatomy Motor end plate on sarcolema on sk muscle Axon potential arrives at axon terminal depolarization of motor  end plate AP along sarcolema, down t tubules stimulates SR to  release Ca (sarcomere contraction) Depolarization caused by AP arriving, voltage channels open up, Ca  ions influx from cytosol into nerve terminal. (Ca ions go into nerve  terminal) o Why depolarization?  Synaptic vessels migrate to terminal cleft and  release acetylcholine, Ca leaves.  Acetylcholine 
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binds to specific receptor, open up gated ion  channel and causes depolarization along motor end  plate region.  Ion channel closed, end plate is  depolarized, the sarcolema membrane and t tubules  depolarize also.  AP causes release of Ca into  cytosol.  Ca concentration in SR is greater than in  muscle cell.  Once Ca is released, sarcomere 
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This note was uploaded on 03/18/2009 for the course IPHY 4650 taught by Professor Robertmazzeo during the Spring '09 term at Colorado.

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Muscle structure and Function Outline - Muscle Structure...

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