Answer: 1234
Explanation:
Depolarization occurs with movement of sodium ions with the negative charges through its channels into the axonplasm to ensure generation of voltage.
At this stage the inside of the neuron (axonplasm is negative)
If the generated voltage is upto the voltage, local current will spread to the next gated sodium channel, more sodium ions diffuse into the axoplasm; If the threshold voltage is sustained, this generate action potential over the axon length
Continuous firing of action potential, above the threshold makes the sodium gated channels to close (refractive period) and potassium channels to open. Therefore potassium ions move out down their concentration gradient (with their positive charge) from the axoplasm (cytoplasm of the neuron) to the cytosols. Making the axoplasm to be more negative this is REPOLARISATION.
In a resting neuron, potassium ions are pump in, with the positive charges and sodium ion channels open, for sodium ions to be pumped out into cytosol caring the negative charges along. This is resting membrane potential. Although some potassium ion channels leaks for potassium ions to move back in to the axoplasm by active transport, against the concentration gradient.
Note. Potassium ion is in intracellular, sodium ion is extracellular
