Final answer:
Na+ ions flow into the neuron when sodium-gated channels open, causing depolarization of the neuronal membrane by making the inside less negative. This supports option b) Flow into Depolarization.
Step-by-step explanation:
When sodium-gated channels open during a graded potential, Na+ ions will tend to flow into the neuron. This influx of positively charged sodium ions into the neuron results in the interior of the cell becoming less negative compared to the outside, a process known as depolarization. The answer to the student's question is therefore b) Flow into; Depolarization.
A. These ions get into the cell through the sodium-gated channels that open in response to various signals, such as neurotransmitters binding to their receptors or changes in the electrical state of the neuron.
B. This flow of sodium ions into the neuron changes the relative charge inside the neuron by making it more positive compared to the exterior. When enough Na+ ions enter to sufficiently change the membrane potential, it can lead to the initiation of an action potential if the threshold is reached.