BCM 475 Chapter Notes - Chapter 13: Positive Feedback, Cell Signaling, Neurotransmitter

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16 Oct 2016
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Respond to physical/chemical changes precisely timed conformational changes. Interior of neuron contains high k+ concentration and low na+ concentration: gradient is generated by na+-k+ atpase. Electric potential determined by ratio of internal:external ion concentrations. Resting state: membrane potential = -60mv: action potential membrane potential depolarized below threshold (i. e. -40mv) Becomes positive before returning to negative (repolarization) Action potentials arise from large, transient changes in axon membrane permeability. Channels must quickly open in response to changes in membrane potential: depolarization of membrane beyond threshold, increase in na+ permeability, na+ ions flow into cell due to electrochemical gradient across plasma membrane, further depolarization. More increase in na+ permeability: positive feedback very rapid/large change in membrane potential (-60 mv +30mv, membrane becomes less permeable to na+ and more permeable to k, k+ flows out, membrane potential becomes negative. Resting level of -60mv is restored as k+ conductance decreases. Enables measurement of (channel activity) ion conductance through small patch of cell membrane.

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