NervSystemNotes

NervSystemNotes - Biology 100, Fall 2005 (11/27/05) Notes...

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Biology 100, Fall 2005 (11/27/05) Notes on the Nervous System (see Chap 45) The Resting Potential : Inside of axon is negative (approx. -70 mV ) when there are no nerve impulses occurring Special Terms: Depolarization = more positive (upward from the resting level) Hyperpolarization = more negative (downward from the resting level) The Action Potential = Nerve Impulse: Ion Gradients ---------> Electrical Signal (nerve impulse) -- Na + conc. high on outside -- K + conc. high on inside --> Gradients maintained by action of Na-K pump (which uses ATP) Signal: -70 mV --> +30 mV --> -70 mV ==> 100 mV amplitude How the Action Potential "works": "stimulus" --> depolarization --> Na + gates open --> Na + enters axon --> more depol. --> more Na + entry --> more depol. --> etc., etc., etc. --> inside positive (+30 mV) Na + gates close automatically ; meanwhile, K + gates open --> K + flows out --> resting potential restored (-70 mV) 1
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For every action potential: Na flows into the axon, after which K flows out of the axon. -
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NervSystemNotes - Biology 100, Fall 2005 (11/27/05) Notes...

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