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BIOG 1440 (69)
Buchon, N (6)
Lecture 21

BIOG 1440 Lecture 21: Action Potential

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Biology: General Courses
BIOG 1440
Buchon, N

Book Action potentials are the signals conducted by axons Graded potential: shift in membrane potential Magnitude varies with strength of stimulus Induce a small electric current that leaks out of neuron Decay with time and with distance from source Action potential: massive change in membrane potential Constant magnitude and can regenerate in adjacent regions of the membrane Can spread along axons well suited for long distances Arise because of voltagegated ion channels voltage gated ion channels: openclose depending on membrane potential Occur whenever a depolarization increases membrane voltage to a threshold value Threshold: value of membrane potential at which neurons fire Generation of action potentials Depolarization opens both types of channels but they respond independently and sequentially Sodium channels open first, initiating action potential As action potential proceeds, sodium channels become inactivated they remain inactive until resting potential Potassium channels open more slowly but remain open throughout action potential (see detailed process in page 16 of notes) Refractory period: downtime where a second action potential cannot be initiated Limits frequency at which action potentials can be generated Ensures that all signals travel in one direction Caused by inactivation of Na+ channels, not change in ions
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