Lecture 3 Extra-cellular fluid= high in NaCl, Low in K Intra-cellular fluid=high in K, low in NaCl-voltage difference created between inside and outside of axons-about 70 millivolts voltage of outside is 0, inside is -70 millivolts, of -.07 volts Neurons transmit their signals by using frequency modulation-all their action potentials (spikes) have the same amplitude (i.e. neurons don’t use amplitude modulation (AM)) Action Potential 1st- assume some stimulus caused the voltage of membrane to go from -70 to -65 2nd- sodium channels open up in the membrane and Na+ goes into cell because of diffusion and electric-al charge 3rd- Potassium channels open, also because of voltage change, and K+ leaves the cell. (because so much sodium, that inside of cell is no longer negatively charged 4th- Sodium channels close, inside of cell becomes negative, sinec K+ is still getting out of cell 5th- Once voltage reduces near -.07, potassium channels close because they are voltage dependent-when the membrane potential returns to its resting state, what happens with the excess
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