BIOL 2P05 Lecture Notes - Sarcomere, Troponin, Depolarization
13 Jan 2013
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Document Summary
Role of atp and phosphocreatine in providing the energy. Stimulation of muscle fibres by the nervous system. Contraction myosin heads attach to actin binding sites / form temporary cross bridges / bridges rapidly break and reform / new cross bridges form further along actin filament / causing shortening of each sarcomere. When stimulation stops ca2+actively taken up by sarcoplasmic reticulum / myosin head detaches from actin / cross bridges reform / muscle relaxes. No atp available cross bridges cannot detach / muscle becomes stiff / unable to relax / extreme form: rigor mortis / occurs after death. Cycle of events during contraction of a myofibril. Ca2+ ions enter sarcoplasm during wave of depolarisation. Bind to troponin / changes shape of protein / removes block of tropomyosin / exposes actin binding sites. Atp binds to myosin / stimulates atpase / releases energy. Allows myosin heads to form cross bridges with actin.
