BIOLOGY 3P03 Lecture Notes - Lecture 7: Squid Giant Axon, Action Potential, Resting Potential
19 Oct 2017
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Document Summary
Based on the experiments of hodgkin and huxley (1950"s) using the squid giant axon, we summarized the underlying ionic mechanisms of the action potential. The squid axon preparation was an important development by j. 1930"s: key was that the large size of the squid axon (500 - 1000 m) in diameter, which allowed wire electrodes to be inserted axially, permitting measurements of em, etc. Note: intracellular glass electrodes (with ne tips) for membrane penetration were developed much later. Peak of an ap fails to reach ena. By the ap peak, gk has already increased substantially. K+ can carry out some of the charge brought in by na+ and vm never reaches ena: why? gk has already increased on the upstroke and gna has already been partially inactivated. States of voltage-gated na+ and k+ channels during ap. Resting state: m" closed; h" open; "n" closed. Depolarizing phase: m" open; h" open; "n" closed. Repolarizing phase: m" open; h" closed; "n" open.
