Question

During resting stage, the axonal membrane is

• A. More permeable to $N{a}^{+}$ and nearly impermeable to $K^{+}$
• B. More permable to $K^{+}$ and nearly impermeable to $N{a}^{+}$
• C. Permeable to both
• D. Impermeable to both

Answer 1

Answer: (B)

More permable to $K^{+}$ and nearly impermeable to $N{a}^{+}$

During the resting potential, sodium channels are completely closed, but potassium channels are partly open, so potassium can flow slowly out of the neuron.

As an action potential travels down the axon, there is a change in polarity across the membrane. The $N{a}^{+}$ and $K^{+}$ gated ion channels open and close as the membrane reaches the threshold potential, in response to a signal from another neuron.

At the beginning of the action potential, the $N{a}^{+}$ channels open and $N{a}^{+}$ moves into the axon, causing depolarization.

Repolarization occurs when the $K^{+}$ channels open and $K^{+}$ moves out of the axon. This creates a change in polarity between the outside of the cell and the inside. The impulse travels down the axon in one direction only, to the axon terminal where it signals other neurons.