Put the following action potential events in order. i) regenerative na+ influx occurs at the threshold potential ii) weak na+ influx and strong k+ efflux iii) continuous k+ efflux causes the membrane potential to become more negative than resting potential iv) strong na+ influx and weak k+ efflux.

i) iv) ii) iii)

Explanation:

The excitable cell begins being in a resting state, with a negative charge, -70 mV. First (i) there is a stimulus of influx of sodio into the cell, if the stimulus is strong enough and exceeds -55 mV, the threshold potential, then an action potential will occur. (iv) A strong influx of sodium that deporalizes the cells causes a change to a positive charge in the cell. (ii) Then potassium efflux from the cell in large quantities, which repolarizes the cell. (iii) With a continuous efflux of potassium the cell can become more negative than the resting potential, this is called hyperpolarization.

the answer that best describes the relative refractory period in the neuron is the resting membrane potential is restored, but concentrations of sodium and potassium are not restored to their original state.

the refractory period is the time during which another stimulus given to the neuron will not lead to a second potential. thus, because na+ channels are inactivated during this time, additional depolarizing stimuli do not lead to new action potentials.  

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