Question

The axoplasm becomes increasingly negative because of

• A. sodium ion efflux from axoplasm to ECF
• B. potassium ion efflux from axoplasm to ECF
• C. chloride ion influx from ECF to axoplasm
• D. phosphate influx from ECF to axoplasm

Answer 1

The correct option is B potassium ion efflux from axoplasm to ECF

The axoplasm becomes increasingly negative because of potassium ion efflux from axoplasm to ECF. Axolemma has more potassium leakage channels than sodium leakage channels. The number of potassium ions that diffuse down their concentration gradient out of the cell into the ECF is far greater because potassium leakage channels are leakier than sodium leakage channels.
Sodium and chloride ions are richly found in the ECF. They are found in very low concentration inside the axoplasm.
Phosphates are richly found in the axoplasm.