Question

What starts the change in a cell's membrane potential leading to an action potential? What is depolarization (which ions move which way)? What would be the result of blocking sodium channels? What happens during an action potential ( is it depolarization or repolarization and is it the flow of sodium or potassium)?

Answer 1

An action potential is an all-or-nothing event that involves depolarization and repolarization of the cell membrane. Sodium channels open during depolarization, allowing sodium ions to enter the cell and increase its positive charge. Potassium channels then open during repolarization, allowing potassium ions to leave the cell and restore its negative charge.

Step-by-step explanation:

An action potential is an all-or-nothing event; it either happens or it does not.

The threshold of excitation must be reached for the neuron to "fire" an action potential.

As sodium ions rush into the cell, depolarization actually reverses the charge across the membrane from -70mV to +30mV.

This change in the membrane potential causes voltage-gated K+ channels to open, and K+ begins to leave the cell, repolarizing it.

At the same time, Na+ channels inactivate so no more Na+ enters the cell. K+ ions continue to leave the cell and the membrane potential returns to the resting potential.