PHY122_L08 - PHY122 PHY122 Physics for the Life Sciences II...

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PHY122 PHY122 – Physics for the Life Sciences Physics for the Life Sciences II II Lecture 8 Currents and Resistance Note: Clicker Channel 21 09/22/2011 1 Lecture 8
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Electricity in the Body: Nerves Typical nerve cell: Cell body: genetic control and energy management Dendrites: input of chemical stimuli across synapses Axon: propagation of the electrical stimulus 09/22/2011 2 Lecture 8
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Simplified electric model Membrane is a dielectric insulator ( κ 9 ) contains: Na + channels body axon K + channels Na + -K + pumps h i h i l t f 3N + t d 2K + i t f 7 membrane 3.6 10 m  C Q +Q E R S physio-chemical pump: transfers 3Na out and 2K in per transfer, leaving the cell inside at –70 mV with respect to the outside + + + + + + membrane V E –Q 3 6 cross section f E =0 + + + + E ~7 nm membrane d 70 mV Schematic diagram of an ion h l ( + + ) of axon 0 E =0 + + + 7 nm 10 MV/m 2 channel (Na or K ): 1. 4-6 homologous repeat domains, 2. outer vestibule, h i h l i fl + + + + 09/22/2011 3 Lecture 8 2. outer vestibule, 3. selectivity filter, 5. phosphorylation site, 6. membrane when an ion channel opens, ions flow from the side with the higher concen- tration to the side with the lowest
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