unit2labquiz - Electromyography Lab Study Guide 1. Define...

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Electromyography Lab Study Guide 1. Define and draw the skeletal muscle tonus. - the state of partial contraction of muscles even at rest - maintained by activation of a few motor units at all times 2. Define and draw the steps of excitation coupling. - sequence of events by which an action potential in the plasma membrane of a muscle fiber leads to the cross-bridge activity 1. action potential initiated and propagates to motor neuron axon terminals 2. Ca2+ enters axon terminals through voltage-gated Ca2+ channels 3. Ca2+ conc increase triggers release of ACh from axon terminals 4. ACh diffuses from axons terminals to motor end plate in muscle fiber 5. ACh binds to nicotinic receptors on motor end plate, increasing permeability to Na+ and K+ 6. more Na+ moves into fiber at motor end plate than K+ moves out, depolarizing the membrane and producing the end-plate potential (EPP) 7. local currents depolarize the adjacent muscle cell plasma membrane to its threshold potential, generating an action potential that propagates over the muscle fiber surface and into the fiber along the T-tubules 8. action potential in T-tubules induces DHP receptors to pull open Ryanodine receptor channels, allowing release of Ca2+ from lateral sacs of SR 9. Ca2+ binds to troponin on the thin filaments, causing tropomyosin to move away from its blocking position, thereby uncovering cross-bridge binding sites on actin 10. energized myosin cross-bridges on the thick filaments bind to actin 11. cross-bridge binding triggers release of ATP hydrolysis products from myosin, producing an angular movement of each cross-bridge 12. ATP binds to myosin, breaking linkage between actin and myosin and thereby allowing cross-bridges to dissociate from actin 13. ATP bound to myosin is split, energizing the myosin cross-bridge 14. cross-bridges repeat steps 10-13, producing movement (sliding) of thin filaments past thick filaments. Cycles of cross-bridge movement continue as long as Ca2+ remains bound to troponin 15. cystosolic Ca2+ conc decreases as Ca2+-ATPase actively transports Ca2+ into SR 16. removal of Ca2+ from troponin restores blocking action of tropomyosin, the cross-bridge cycle ceases, and the muscle fiber relaxes 3. Define concentric contraction, eccentric contraction, and isometric contraction. - isotonic – muscle length changes; load remains constant - concentric – muscle shortening; tension exceeds load; cross-bridges bound to actin rotate thru power stroke shortening of sarcomeres - eccentric – muscle lengthening; load exceeds tension; object being supported by muscle contraction is lowered; not an active process due to external forces on muscle - isometric – develops tension, but doesn’t change length; when muscle supports load in a constant position; when muscle tries to move a load greater than the tension developed by muscle 4. Describe what is physiologically occurring in the sarcomere during each of the contraction types. - concentric – cross-bridges bound to actin rotate thru power stroke
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This note was uploaded on 03/27/2012 for the course PHYSIOLOGY 335 taught by Professor Strang during the Spring '11 term at Wisconsin.

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unit2labquiz - Electromyography Lab Study Guide 1. Define...

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