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BIOL1412 01 15 2014.docx

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Biological Sciences
BIOL 1412
Paul Messing

BIOL1412 01 15 2014 Factors establishing RMP: 1) Na+/K+ -ATPase (Na+/K+ pump) -not a channel -> Effects: a) maintain [ ] gradients of Na+ and K+ b) contributes a little (a few mV) to RMP (pumping more +ve ions out than in) 2) org* inside cell - can't cross membrane 3) More non-gated K+ channels than non-gated Na+ channels (Fig. 11.8) (membrane more permeable to K+ than Na+ at rest therefore, K+ is the major determinant of RMP) - K+ diffuses out of cell down [ ] gradient therefore, cell losses +ve charge (inside becomes more -ve) - unlike charges attract and K+ diffusion as inside becomes increasingly -ve - Na+ diffusion in increases due to increasing attraction to -ve cell interior - until -70mV reached, +ve out (K+) is greater than +ve (Na+) in greater K+ permeability - once at -70mV, the amount of +ve (K+) moving out equals the amount of +ve (Na+) moving in - force on Na+ much higher than on K+ - therefore, The net movement of charge (ions) is 0 (equal in both directions): RMP of -70mV Neuronal Physiology B. Electrically Excitable Cells * ONLY muscle and nerve cells * capable of producing departures from RMP in response from RMP in response to stimuli (=changes in the external or internal env't) * When a neuron is stimulated: 1) gated ion channels open 2) MP (membrane potential) changes = producing a grade potential (GP).
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