C_S_D 4430 Lecture Notes - Lecture 7: Resting Potential, Tetraethylammonium, Sodium-Potassium Alloy
Document Summary
Discovery of the membrane mechanism underlying the action potential. Two currents that drive the ap: inward flow of positive ions. Begins very soon after the voltage clamp is set (cell is depolarized beyond threshold) Declines to nothing in about 3 milliseconds: outward flow of positive ions. Begins about 1 millisecond after the voltage clamp is set. Continues as long as the voltage clamp is on. Ion currents verified through use of two toxins. Known to block na+ ion channels (deadly, blocks action) *proved movement of na+ as source of first current. *proved movement of k+ was source of second current. The inner gate voltage sensor voltage sensor opens the gate when depolarization beyond threshold occurs. The inactivation gate remains closed for a specific amount of time, if depolarization beyond threshold occurs while the inactivation gate is closed, ions cannot flow through despite opening of the voltage sensitive inner gate. Gate has a voltage sensor and a timing mechanism.
