Question

What STIMULUS caused resting potential to move towards 0mv and what occurs at -55mv?

Answer 1

An action potential is a change in membrane potential in response to a stimulation. A stimulation can be a heat shock or pain which was received by receptor present in the skin or the place where shock has been given. An action potential divied into four phases that correlate with changes in sodium and potassium ion permeability of the plasma membrane of nerve cell. These are resting, depolarization, repolarization, and hyperpolarization phases. The resting phase of action potential where neuron has a membrane potential of -70 mV, which is maintained by the potassium leaky channels. When any stimulus stimulate the opening of the gate of potassium voltage gated channels, potassium ions will move into the cell acroos membrane through the voltage gated channels which causes membrane potential to decrease beyond theshold level -50mV. This decrease in membrane potential is called depolarisation phase of the action potential. The action potential can be generated only when the reduction in membrane potential beyond the threshold level (-50 mV). If the initial depolarization does not exceed the threshold level, then the action potential will not proceed and the membrane potential will return to the resting potential. If the threshold is exceeded, then the voltage-gated sodium channels are opened and there is a rapid inflow of sodium ions, reversing the membrane potential from a negative value to a positive value. Depolarization occurs only in less than one millisecond, then the voltage-gated sodium channels are inactivated. Depolarization triggers the voltage-gated potassium channels to open, to set back the membrane potential to resting value, this phase is called repolarization. The voltage-gated potassium channels are slow to close after the change in membrane potential which cause the membrane potential to reach more that resting value, reaching more than resting of membrane potential is called hyperpolarization. The potassium leaky channels reestablish the resting membrane potential, during this period, the sodium channels are restored to the active, but closed state and this axon portion is ready to undergo next action potential in response to further stimulation.