36. Electrical signaling II

36. Electrical signaling II - excite.org(anism Electrical...

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1 excite.org(anism): Electrical Signaling Today’s lecture – we’ll use clickers Review today – 11:30-1:00 in 2242 HJ Patterson The Neuron - F. Fig. 45.3 •Electrical signals –Dendrites: graded post-synaptic potentials –Axons: all-or-none action potentials Chemical signals – Synapses: neurotransmitters Key concept: different structures, different proteins, different functions Electrical signaling occurs via membrane proteins Membrane proteins controlling ion flow across membranes pumps - use ATP to move ions against their electrochemical gradients - (e.g., Na + /K + pump or H + pump) - slow rates of ion transport carriers (transporters) - undergo conformational changes that carry solutes/ions down electrochemical gradients - intermediate transport rates channels - form aqueous pores for solutes/ions to diffuse down electrochemical gradients - fast (!) transport rates channel carriers pump Different roles in electrical signaling for different proteins Animal cell membranes - Na + /K + pump uses ATP to establish K + and Na + electrochemical gradients Na + /K + pump maintains Na + and K + electrochemical gradients transports Na + out of cell for nutrient assimilation and osmoregulation transports K + into cell --> first step toward generating membrane potential, i.e., the composite of the electrical components of all electrochemical gradients = the electrical charge difference across the membrane (voltage) adds several mV by itself to membrane potential F. Fig. 45.5
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2 Channel proteins - electrical signaling channels - form aqueous pores with selectivity filters for particular solutes/ions to diffuse down their EG gradients always open closed open leak channels gated channels Alberts et al. Figs. 11.03 and 11.20 Channel proteins - electrical signaling For example, voltage-gated Na + channel F. FIG. 45.9 Channel proteins - electrical signaling channels - form aqueous pores with selectivity filters for particular solutes/ions to diffuse down their EG gradients always open closed open leak channels gated channels Telegraphing the story … Membrane potential (entire neuron) - Na + /K + pump, K + and Na + leak channels Action potential (axon) - voltage-gated Na + and K + channels Post-synaptic potentials (dendrites) - neurotransmitter-gated Na + , K + , and Cl - channels (also called ligand-gated) Alberts et al. Figs. 11.03 and 11.20 F Fig 45.3 and 45.4 Membrane potential Sum of electrical components of all electrochemical gradients is known as the resting (or steady-state) membrane potential.
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