Terms in this set (138)

- This is the upward deflection from the resting membrane potential
- This is when voltage gated Na channels are opened because graded potential was big enough to reach threshold or Sum of graded potentials was big enough to reach threshold
- NA enters the cell, taking positive charges into the cell, and starts to make membrane even more positive
- As more and more NA enters the cell, membrane more and more positive, more depolarized
- And the more membrane is depolarized, the more voltage gated Na channels are opened
- This is a vicious cycle (This is an e.g. of positive feedback)
- This opening of voltage gated Na channels results in rapid upswing of membrane potential towards some value
- The membrane is depolarized and the membrane potential surges to +60mv, which is the equilibrium potential for Na
- Recall - that if Na had its way, if voltage gated Na channels were opened, then the Na ions will now become the dominant current, Na would want the membrane to be sitting at +60mv at its equilibrium potential; sadly, Na never gets to reach this point - only gets to +30mv
- One of the reasons why the membrane potential doesn't reach +60mv is bc soon after the voltage gated Na channels open, about ½ millisecond the voltage gated Na channels start to inactive - thus the membrane potential doesn't ever get to +60mv
- Before membrane potential had a chance to reach +60mv with Na influx, the voltage gated Na channels are inactivated and no more Na comes into the cell - only reaches +30mv
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