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Muscle Contraction and Relaxation

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Caroline Ward

on 6 November 2012

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Transcript of Muscle Contraction and Relaxation

Muscle Contraction And Relaxation Muscle Contraction is: a complex interaction of several cellular and chemical constituents. The final result is a movement within the myofibrils in which the filaments of actin and myosin slide past one another, shortening the sarcomeres. When this happens, the muscle fiber shortens and pulls on its attachments. What is Muscle Contraction? ACh binds to Ach Receptors. Step: 3 Calcium ions diffuse from the sarcoplasmic reticulum into the sarcoplasm and bind to troponin molecules. Step: 6 Muscle Relaxation
Step:1 Calcium ions are actively transported into the sarcoplasmic reticulum . Step:2 ATP breaks linkages between actin and myosin filaments without the breakdown of ATP itself. Step: 3 Breakdown of ATP "cocks" the cross bridges. Step: 4 Troponin and tropomyosin molecules inhibit the interaction between myosin and actin filaments. Step: 5 BY: Caroline Ward Anatomy 2nd period In the neuromuscular junction! Where does this happen? Neuromuscular Junction-Synapse between motor neuron and a skeletal muscle fiber.
Synapse-Functional connection between the axon of one neuron and the dendrite or cell body of another neuron or another cell type. Step: 1 A nerve impulse travels down a motor neuron. Step: 2 The motor neuron terminal releases the neurotransmitter acetylcholine (ACh) Neurotransmitter- chemical that an axon end secretes to stimulate a muscle fiber to contract or a neuron to fire an impulse.
Acetylcholine-type of neurotransmitter, which is a biochemical secreted at axon ends of many neurons; transmits nerve messages across synapses. Step: 4 The sarcolemma is stimulated, and a muscle impulse travels over the surface of the muscle fiber deep into the fiber through the transverse tubules. Sarcolemma-cell membrane of a muscle fiber.
Transverse tubule-membranous channel that extends inward from a muscular fiber membrane and passes through the fiber. Step: 5 The muscle impulse reaches the sarcoplasmic reticulum and calcium channels open. Sarcoplasmic reticulum-membranous network of channels and tubules within a muscle fiber, corresponding to the endoplasmic reticulum of other cells. Troponin-protein that functions with tropomyosin to block muscle contraction until calcium ions are present. Step: 7 Tropomyosin molecules move and expose specific sites on actin actin-a protein in a muscular fiber that forms filaments that slide between filaments of the protein myosin, contracting muscle fibers. Step: 8 Actin and myosin form linkages myosin-protein that, with actin, contracts and relaxes muscle fibers. Step: 9 Thin (actin) filaments are pulled toward the center of the sacromere by myosin cross bridges. Cross bridges-globular parts, or heads that project outward along the lengths of the two twisted strands of a myosin molecule. Step: 10 The muscle fiber shortens and contracts Acetylcholinesterase decomposes acetylcholine and the muscle fiber membrane is no longer stimulated. Acetylcholinesterase-enzyme that catalyzes the breakdown of acetlycholine. Step: 6 Muscle fiber remains relaxed yet ready until stimulated again. THE END The 10 steps to muscle contraction and the 6 steps to muscle relaxation.
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