Sodium-Potassium Chunking

State of neuron at rest (step 1)

At rest, there is a greater concentration of Na outside the neuron and K inside the neuron. This leads to a difference in concentration and in electrical potential across the impermeable membrane (about -70mV), which is known as the resting potential.

Opening of NA⁺ gates (step 2)

Na+ gates are voltage-sensitive (they require the resting voltage to be about -55 – -60 mV). If a sufficient increase in voltage is input from the dendrites, depolarization will occur: Na+ channels open, and Na+ rushes into the neuron, making the neuron much more positive.

Opening of K⁺ channels (step 3)

Slightly later, K+ gates open and allow K+ to leave the neuron

Peak action potential (step 4)

At the peak of the action potential (~+40mV), the flow of Na in is equal to the flow of K+ out

Beginning of repolarization (step 5)

The flow of Na+ in wanes, while K+ out continues, repolarizing the neuron and making it less positive to about -80 mV

Restoration of resting potential (step 6)

A Na/K pump then removes Na and imports K to restore the resting potential using ATP