Lecture8.Nerve.to.Muscle

Lecture8.Nerve.to.Muscle - LS2 Nerve to Muscle Prof. George...

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LS2 Nerve to Muscle Prof. George V. Lauder Office Hours: Friday 2-3 (after class), and by appointment. Today: We complete our initial discussion of the nervous system by reviewing neural integration. Then we begin our discussion of muscle as a tissue and address the process of muscle contraction. Next time: The neuromuscular junction and whole muscle mechanics ***focus on material that explains in more detail topics covered in lecture*** Assigned Reading for this week: Custom text, pp. 274-316 (green page #s)
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Lecture outline Neural integration reviewed – EPSP, IPSP, from graded potentials to action potentials From nerve to muscle Structure of striated muscle: sarcomeres, actin, myosin, titin, Mechanisms of muscle contraction The sliding filament mechanism The cross-bridge cycle Regulation of muscle contraction by calcium, troponin and tropomyosin
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Graded potentials can be excitatory : moving the membrane toward threshold (about – 55 mV) or Inhibitory : moving the membrane below the resting potential (about – 70 mV) Graded potentials decay over distance. Graded potentials – from last lecture Usually occur on the neuron cell body Usually 0.5 to 5 mV in size (small)
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An action potential is an “all-or-none” sequence of changes in membrane potential (and an example of positive feedback) . Action potentials result from changes in ion permeability due to the operation of voltage-gated Na + and K + channels. The rapid opening of voltage-gated Na + channels allows rapid entry of Na + The slower opening of voltage-gated K + channels allows K + exit Action potentials – from last lecture threshold ~ -55 mV
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Review -- flash animation of the synapse NOTE: 1. The role of voltage-gated calcium channels 2. Vesicles with neurotransmitter 3. Neurotransmitter binding to postsynaptic receptors (often ligand-gated ion channels) 4. Re-uptake and enzymatic breakdown of neurotransmitter 5. At an excitatory synapse non-selective ion channels open and ions (Na+ , K+ ) move down their gradients 6. At an inhibitory synapse Cl- and/or K+ channels open
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Key point: An action potential in a
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Lecture8.Nerve.to.Muscle - LS2 Nerve to Muscle Prof. George...

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