BISC306 Lecture Notes - Lecture 5: Relative Permeability, Voltmeter, Active Transport
16 Feb 2017
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Document Summary
Experiments using squid giant axons reveals action potential. A stimulus strong enough to cause contraction of muscle produced action potential. Measuring voltage differences across membranes: measurements usually expressed in millivolts (mv, resting membrane potential between -20 mv to -100 mv. Model of membrane reflecting its electrical properties: current can always move across a channel; membrane is a resistor. Capacitance current: electrolytes are not going across the membrane, charging a capacitor. Steady state when at rest: steady state is maintained by active transport; na+/k+ atpase, solid lines depict active transport, uphill and non-spontaneous; exergonic, dotted lines represent diffusion; downhill; favored. Refractory period and accommodation: the slower an axon or other excitable cell is depolarized towards threshold, the more positive the threshold becomes. If depolarization is very slow then it may not be able to elicit an action potential. Some neurons will only generate a few action potentials or slow down the frequency of transmission when they are held above threshold.
