Lecture 3 - Nervous System

Navoltagegated channel to be able to be ac4vated a

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Unformatted text preview: channels (at +40 mV) Opening of K+ ­voltage ­gated channels Voltage ­gated Voltage ­gated Na+ channels K+ channels Inac7vated OPEN Cytosol 21 Step – 5 Hyperpolariza4on 5. K+ ­voltage ­gated channels open slower than Na+ and are kept open for longer brings back the res4ng poten4al Hyperpolariza4on (undershoot) Delay in closure of K+ voltage ­gated channels 5 Voltage ­gated Voltage ­gated Na+ channels K+ channels Closed Cytosol OPEN 22 Step – 6 Res4ng poten4al 6. Closure of K+ ­voltage ­gated channels and ac4on of Na+/K+ pump restores the res4ng poten4al 6 1 Voltage ­gated Voltage ­gated Na+ channels K+ channels CLOSED CLOSED Cytosol 23 Propaga4on of ac4on poten4al  ­ Axon Closed Na+ channels Open Na+ channels Inac4vated Na+ channels •  Refractory period: Delay of Na+ ­voltage ­gated channel to be able to be ac4vated a second 4me and sustained opening of K+ ­voltage ­gated channels 24 Propaga4on of ac4on poten4al  ­ Axon Closed Na+ channels Open Na+ channels Inac4vated Na+ channels •  Refractory period: Delay of Na+ ­voltage ­gated channel to be able to be ac4vated a second 4me and sustained opening of K+ ­voltage ­gated channels 25 Propaga4on of ac4on poten4al  ­ Axon Closed Na+ channels Open Na+ channels Inac4vated Na+ channels •  Refractory period: Delay of Na+ ­voltage ­gated channel to be able to be ac4vated a second 4me and sustained opening of K+ ­voltage ­gated channels •  The refractory period prevents the membrane poten4al from reaching a threshold and fire an ac4on poten4al in the reverse direc4on 26 Ac4on Poten4al firing •  Depolariza4on (Ac4on Poten4al starts) •  Propaga4on of signal •  Release of neurotransmiOers 27 Synapses Presynap4c Neuron Postsynap4c Neuron •  Each type of nerve cell releases only one type of neurotransmiOer (presynap4c neuron) •  Postsynap4c neuron can bind to different kinds of neurotransmiOers •  Ca2+ ­voltage ­gated channels open at the end of the axon driving the release of neurotransmiOers 28 hOp://www.hhmi.org/biointerac4ve/molecular ­mechanism ­synap4c ­func4...
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