Muscle Physiology 1

Muscle activity must be replenished immediately from

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Unformatted text preview: troponin FINISH Gating of Sarcoplasmic Reticulum calcium Channels Voltage- gated opening: 2 steps Coupled to T tubules by ryanodine and DHP receptors Calcium- induced opening/closing Conduction of the Action Potential: T tubules are extension of the sarcolemma SR stores Ca2+ via ATP- dependent Ca2+ pump SR has voltage- gated Ca2+ channel Channel response from T tubule depolarization Activates voltage- sensitive DHP receptors DHP = dihydropyridine Activates ryanodine receptors on SR Ca2+ channel As the Ca2+ enters the cytosol, some binds to other voltage dependent SR Ca2+ channels causing them to open as well Ca2+ in cytosol binds to troponin elements Termination of Contraction: Cease input from motor neuron Ca2+ binds low affinity sites to close channels Ca2+ leaves troponin Tropomyosin blocks myosin- actin binding Ca2+ back to the SR by Ca2+ ATPase in SR Transports calcium from cytosol into SR ATP Needs in Muscle: Muscle crossbridge cycle Split ATP by myosin ATPase (power stroke) Bind fresh ATP to myosin (dissociation) Active transport of Ca2+ into SR relaxation Na/K pump maintains he ion gradients, membrane pot...
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