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From node node until reaching terminal end conduction

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Unformatted text preview: l patch prd of membrane, not entire neuron) of • Absolute refractory prd= time btw start of AP & return to RMP • Relative refractory prd= time btw RMP & end of hyperpolarization Signal Conduction in unmyelinated fibers= chain reaction of AP’s chain down entire fiber (or depolarizing ‘segments’ of membrane) until signal reaches terminal end signal • Nerve signal= traveling wave of excitation made by series of AP’s ation • Can’t travel ‘up’ axon because of refractory prd Signal Conduction- Myelinated Fibers Signal Nodes of Ranvier are ‘packed’ w/ voltage-regulated ion gates since myelin sheaths of internodes ‘block’ Na from entering since • Thus, signal ‘jumps’ from node-node until reaching terminal end Conduction very rapid down each internode, but does weaken • NR spaced ~1mm apart so new AP’s are generated per/node • Saltatory conduction= propagation of a nerve signal that ‘jumps’ propagation from node to node from Synapses- pre & postsynaptic neurons • Electrical (gap junctions) & chemical synapses chemical • Neurotransmitters allow c.synapses to ‘communicate’ Neurotransmitters to • Presynaptic neuron houses synaptic vesicles & postsynaptic Presynaptic neuron has receptors & ligand-regulated ion gates ligand-regulated Neurotransmitters & Regulated Messengers Messengers 100+ neurotransmitters discovered so far: ACh & 3 classes 100+ according to chemical composition according • As science progresses, neurotransmitters, hormones, & As other messengers are becoming difficult to distinguish other Typical neurotransmitter= sm organic compound synthesized sm by pre-, released into s.cleft, bind to sites on post-, & alter physiology of 2nd cell physiology • Receptor determines effect of neurotransmitter has on post• Same chemical has many different types of receptors, & so, a Same neurotransmitter doesn’t have same effect ev...
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