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Published byCameron Flynn Modified over 9 years ago
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Muscle Contraction
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1.Acetylcholine (Ach) is released from the axon terminal (nerve) into the synaptic cleft and binds to Ach receptors in the sarcolemma (muscle cell)
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2. Action potential is generated and muscle fiber becomes excited 3. Calcium (Ca 2+ ) is released from the sarcoplasmic reticulum 4. Ca 2+ binds to troponin, causing tropomyosin on actin to shift and myosin binding sites become exposed.
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5. ATP binds to myosin head, causing it to be in the “cocked” position. 6. Actin and myosin bind, forming a cross-bridge
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7. Myosin head flexes, causing actin to be pulled along the myosin, shortening the sarcomere (remember, muscles only pull/shorten/contract)
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Muscle Relaxation
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Another ATP molecule releases myosin head from actin. Ca2+ is transported back to the sarcoplasmic reticulum, causing tropomyosin to re-cover the myosin binding site Sarcomere “slides back” to its original position.
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