Neuron Communication: How Action Potentials Work (Animated)

The neuron's resting state is maintained by a careful balance of sodium and potassium ions across its membrane.The cell membrane is made of a phospholipid bilayer, which forms a selective barrier between the inside and outside of the cell.In the resting state, there is a higher concentration of sodium ions outside the cell.Conversely, potassium ions are more concentrated inside the cell.The sodium-potassium pump actively maintains this concentration gradient.For every three sodium ions pumped out, two potassium ions are pumped in, creating an electrical imbalance.This ion imbalance creates a negative membrane potential of negative seventy millivolts.This resting state is essential for the neuron's ability to generate and transmit electrical signals.When a stimulus reaches the threshold potential of negative 55 millivolts, voltage-gated sodium channels begin to open.As the membrane potential reaches threshold, the channels undergo a conformational change, creating openings for sodium ions to flow through.Sodium ions rapidly flow into the cell through these opened channels, following both their concentration and electrical gradients.This creates a domino effect, as the local positive charge triggers neighboring sodium channels to open, propagating the signal along the axon.This rapid change in membrane potential from negative to positive is called depolarization, and it's a crucial part of the action potential.As the membrane reaches peak depolarization, voltage-gated potassium channels begin to open.Potassium ions flow out of the cell through these channels, following their concentration gradient.This outflow of positive potassium ions causes repolarization, returning the membrane potential back toward negative values.During this time, sodium channels enter their inactivated state and cannot be reopened, creating a refractory period.The sodium-potassium pump now works to restore ion concentrations to their original levels.The pump moves sodium ions out and potassium ions back in, preparing the neuron for the next action potential.Finally, all voltage-gated channels return to their resting states, completing the action potential cycle.