Final answer:
When a neuron changes its ion permeability, it typically becomes more positive due to the influx of sodium ions during depolarization, which is part of the process of transmitting an action potential. The correct option is 1).
Step-by-step explanation:
When a neuron changes its ion permeability from the resting state, several events occur that are critical for the transmission of electrical signals. Typically, in its resting state, a neuron has a resting membrane potential of around -70 mV, indicating that the inside of the neuron is negatively charged relative to the outside. This is maintained by the selective permeability of the membrane and the operation of sodium-potassium pumps.
The first channels to open are usually the sodium ion channels, allowing sodium ions (Na+) to rush into the cell, driven by a concentration gradient. This influx of positively charged ions causes the inside of the cell to become less negative and moves the membrane potential closer to zero, a process known as depolarization. Thus, as the ion permeability changes, the answer to the student's question is that the neuron becomes more positive (2). Following depolarization, potassium ions (K+) tend to leave the cell, which ends the action potential by returning the neuron to a negative charge, known as repolarization. Both of these processes—depolarization and repolarization—are critical for conducting an action potential, which is the essential signal that neurons use to communicate with each other.