Once the "threshold" for an action potential is reached what is the sequence of events that occur? 1. potassium channels are activated and potassium ions move out of the neuron. 2. sodium channels are activated and sodium ions move into the neuron. 3. the interior of the neuron becomes more negatively charged than the exterior. 4. the interior of the neuron becomes more positively charged than the exterior.

Action potentials are electric potentials that is usually activated by nerve impulses. The correct sequence is 2-4-1-3. The first phase is depolarization (2) which involves activation of sodium channels which let the sodium ions inside the cell, making the cell membrane more positive in the interior (4). After this happens, the sodium channels will now close and the potassium channels will now open (1) (stimulated by the high intracellular sodium), and potassium ions will leak out the cell, making the cell membrane more negative in the interior (3).

The correct answer is b