01:119:116 Lecture Notes - Lecture 21: Rigor Mortis, Sliding Filament Theory, Myosin Head
15 Mar 2016
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Document Summary
Muscle fiber: long, cylindrical cell, multinucleate, t (transverse) tubules. Inward extensions of plasma membrane: sarcoplasmic reticulum (sr, myofibrils. Sarcomere basic unit of contraction: repeating unit, hundreds end to end, form myofibril, z lines. Join sarcomeres at their ends: each thin filament attached to z line extends partially across sarcomere, myosin filaments. Centered in sarcomere anchored at m line. Thin and thick filament slide past one another. Sliding filament model of muscle contraction: muscle fiber at rest. Myosin binding site of actin proteins along thin filament: motor neuron transmits info. Motor neuron connected with ~150 muscle fibers. Ap in muscle fiber: muscle fibers large. Travels along plasma membrane down t tubules to sr (ca+2 storage) Ca+2 channels open, releases ca+2 into cytosol. Later - ca+2 pump returns ca+2 to sr. Ca+2 binds to troponin complex on thin filaments. Moves tropomyosin away from myosin- binding sites on actin. Atp binding site and actin binding site.
