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Muscle Contraction and Relaxation
Transcript of Muscle Contraction and 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.