PHYC10007 Lecture Notes - Lecture 26: Myelin, Electric Field, Nernst Equation
7 Oct 2018
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Document Summary
Decay across membrane is indicated by discharge equation v=0 : which means that change in voltage decreases exponentially over time during discharging, equation of time change of the potential difference across a membrane: Where v is the potential difference at the time t, r is the resistance and c: v=-70mv for k+ at t=0, when rc = t, around 37% of the initial voltage has been discharged the capacitance. Decay: potential difference decay with distance from the point of perturbation, depends on the axon radius a, the membrane thickness b, the resistivity of the membrane pmembrane, and the resistivity of the axoplasm paxoplasm. Time constant for the membrane is rxc, which represents the duration of an action potential. Axon is a chain of coupled rc circuits. Capacitor charging/discharging at rate given by =rc=3ms defines signal propagation speed. The interior and exterior of the axon are conducting fluid separated by insulating membrane a capacitor; those two compartments have zero electric field.
