BIOLOGY 3P03 Lecture Notes - Lecture 4: Neuroglia, Demyelinating Disease, Afterhyperpolarization

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Rmp is generated by the unequal distribution of ions (k, na, cl) across the plasma membrane. Distribution of ions is maintained by ionic pumps and exchangers. K+ ions are concentrated inside the neuron and tend to flow down their concentration gradient, leading to hyperpolarization (k+ move out making side more ve) The resting membrane is also permeable to na+ and cl- so rmp can range from -70 to -45 mv: significantly positive to ek. Rapidly rising or (cid:858)spike(cid:859) phase of ap is due to a tra(cid:374)sie(cid:374)t increase in na+ permeability or conductance (gna: permeability depends on the voltage depolarize the membrane and both permeabilities change but k lags behind na. Important for the na to be fast and k to be slo(cid:449)er or you(cid:859)ll (cid:374)e(cid:448)er get a(cid:374) ap. Pna/pk goes from resting 0. 02 to 20 & em moves toward ena (+50 mv) as na+ enters via opening of voltage gated na+ channels (increase na permeability)

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