Final answer:
Depolarization occurs when a stimulus makes the neuron's membrane permeable to sodium (Na+) ions, causing the inside of the membrane to become more positive than the outside. Repolarization follows as the membrane becomes impermeable to Na+ ions again and potassium (K+) ions move from high to low concentration. This allows the neuron to transmit electrical signals.
Step-by-step explanation:
An action potential is an all-or-nothing event in a neuron. The depolarization and repolarization during an action potential are caused by movements of ions across the cell membrane. Depolarization occurs when a stimulus makes the membrane permeable to sodium (Na+) ions, causing the inside of the membrane to become more positive than the outside. Repolarization follows as the membrane becomes impermeable to Na+ ions again and potassium (K+) ions move from high to low concentration. This process allows the neuron to transmit electrical signals.