lecture 9-BIO 365R - Transmitter is contained in synaptic...

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1 Transmitter is contained in synaptic vesicles. Fusion of vesicle membrane with membrane of presynaptic neuron causes release of transmitter into synaptic cleft. Transmitter then binds onto receptors on the postsynaptic membrane, and opens the receptors. The opened receptors allow ions to flow into post-synaptic cell, thereby changing the membrane potential. Ions are shown as red balls
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2 Influx of Ca++ is key event leading to transmitter release
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3 Basal lamina The neuromuscular junction is the synapse made between a motor neuron and a muscle fiber and is a very large synapse. The synaptic region on the muscle fiber has a special name, the END-PLATE Bernard Katz (1911-2003) Nobel 1970
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4 nerve Axon that innervates muscle fiber end plate Muscle fiber
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5 From Dr. Wesley Thompson
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6 Stimulation of the nerve always excites skeletal muscle fibers. It generates a synaptic potential that is so large, that it always exceeds threshold and generates an AP in the muscle fiber The synaptic potential at the neuromuscular junction is called an end-plate potential (EPP).
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7 What causes release of transmitter from vesicles? The answer is the influx of Ca++ at the axon terminal through voltage gated Ca++ channels. The Ca++ channels are opened by the depolarization that occurs when an action potential invades the terminal.
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8 Ca ++ = Z 58 log __ [ Ca ++ ]   i [ Ca ++ ]   o Ca ++ = 2 58 log __ [ .0000001M ]   i [ .001M ]   o Ca ++ = 29 log [ .0001]   i [ 1.0]   o Ca ++ 29 log [ 10,000] = Ca ++ = 29  x 4 Ca ++ +116  mV = Equilibrium  Potential  for  Calcium
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9 epp give pulse of Ca ++ thru pipette resting membrane potential is -70 mv Ca ++ pulse and stimulate nerve epp epp resting membrane
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lecture 9-BIO 365R - Transmitter is contained in synaptic...

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