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lecture 5 synaptic transmission

lecture 5 synaptic transmission - Lecture5: Overview...

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9/17/2008 1 Lecture 5: Synaptic transmission Overview 1 Review 1. Review 2. Saltatory conduction 3. Neurotransmitter release 4. Postsynaptic potentials 5. Presynaptic effects 6. Postsynaptic receptors 7. Termination of neurotransmitter release Review Action potential is a very quick large electrical pulse that generates at the axon hillock and travels down the axon towards the terminal button. Action potentials are generated by excitatory stimuli that depolarize the membrane potential to threshold, opening voltage gated sodium channels. The influx of sodium via the voltage gated ion channels produces the rising phase of the action potential and the outflux of potassium via its own voltage gated ion channels produces the falling(repolarization) and hyperpolarization phases. Properties of the voltage gated sodium channel are responsible for the refractory periods.
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9/17/2008 2 Review Action potentials are all or none. The intensity of the excitatory stimulation at the axon hillock does not change the shape of the action potential. The intensity is encoded by the rate of “firing” or by the number of neurons firing. Propagation (spread) of the action potential is referred to as the neural impulse. The axon depolarizes in a sequential fashion from the axon hillock to the presynaptic terminal (terminal button). Travels in this direction due to the refractory period of voltage gated sodium channel The Neural Impulse: Saltatory Conduction Saltatory Conduction —from the Latin saltare (“to jump”) Occurs on myelinated neurons at the nodes of Ranvier .
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