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Skeletal Muscle Contraction - Coggle Diagram
Skeletal Muscle Contraction
Nerve Signal and Action Potential: The process begins with a nerve signal, or action potential, traveling down a motor neuron towards the neuromuscular junction.
Neuromuscular Junction:
At the neuromuscular junction, the nerve signal triggers the release of the neurotransmitter acetylcholine (ACh) into the synaptic cleft.
Muscle Fiber Excitation: Acetylcholine binds to receptors on the muscle cell membrane (sarcolemma), leading to depolarization of the membrane and the generation of an action potential.
T Tubule Activation: The action potential travels along the sarcolemma and deep into the muscle fiber through structures called T tubules.
Sarcoplasmic Reticulum Release: The T tubules stimulate the sarcoplasmic reticulum (SR) to release stored calcium ions (Ca2+) into the cytoplasm of the muscle fiber.
Calcium Binding to Troponin: Calcium ions bind to the regulatory protein troponin, causing a conformational change that moves tropomyosin away from the myosin binding sites on actin.
Cross-Bridge Formation: With the myosin binding sites exposed, myosin heads bind to actin, forming cross-bridges.
Power Stroke: ATP is hydrolyzed, providing energy for the myosin heads to undergo a power stroke, pulling the actin filaments towards the center of the sarcomere.
Muscle Contraction:
The repeated formation and release of cross-bridges result in the sliding of actin filaments over myosin filaments, shortening the sarcomere and causing muscle contraction.
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The Contents of Skeletal Muscle
Myosin, Myosin Head, Myosin binding site
Actin, actin active site, Troponin, Tropomyosin
Sarcomere
I band, A band, H Zone
Nerve
T tubule,
Sarcoplasmic reticulum, terminal cisternae
Calcium
ATP