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10 Action Potentials

10 Action Potentials - Biology141(Physiology 1:02 AM...

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4/6/08 1:02 AM Biology141 (Physiology) Page 1 of 4 https://courses.bio.psu.edu/spring2008/biol141/Lecture%2010(2008).htm Biology141 (Physiology) Lecture 10 M. Whim ACTION POTENTIALS. [1]. BACKGROUND. neurons communicate with each other and with effectors via action potentials (AP’s). AP’s are transient changes in the membrane potential. they arise from brief alterations in the permeability of the cell membrane to ions. [2]. THE GENERATION OF ACTION POTENTIALS. Na and K ion channels are “voltage gated” . They “open” when the membrane potential becomes depolarized. are they open at the resting membrane potential? how do Na and K ions move through Na and K channels? (a). The basic sequence of events occurring during an action potential. the membrane potential at the axon hillock (see lecture 8) depolarizes . once a “ threshold” level of depolarization is reached the voltage gated Na channels open . this leads to an influx of sodium DOWN its electrochemical gradient into the cell (remember Na has an equilibrium potential of +60 mV). the intracellular movement of positive (Na) ions makes the membrane potential further depolarized.
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