Final answer:
To prevent neuron B from firing an action potential, one could equalize or lower extracellular sodium concentration compared to intracellular levels, or utilize TTX, a voltage-gated sodium channel blocker. Other options like eliminating potassium or disabling the Na+/K+ pumps may not be immediately effective in halting an action potential.
Step-by-step explanation:
Adjusting Solutions to Prevent Neuron Firing
To adjust solutions so that neuron B does not fire an action potential at all, one could:
- Make the extracellular sodium concentration equal to or below the intracellular sodium concentration, which can prevent the depolarization that is required for an action potential.
- Subject the neuron to TTX, a voltage-gated sodium channel blocker, which would prevent sodium ions from entering the neuron, precluding the depolarization necessary to reach threshold potential.
- Decreasing the concentration of extracellular potassium to zero would not be effective because it would create a steep gradient for potassium to leave the cell, making the inside more negative and potentially further away from threshold.
- Disrupting the Na+/K+ pumps would eventually prevent the restoration of resting potential, but would not directly prevent an action potential if the membrane is already at or near threshold.
To terminate an action potential, potassium and sodium ion pumps and channels play crucial roles. Sodium ion channels open first, allowing positively charged sodium ions into the neuron causing depolarization. Soon after, potassium channels open, allowing potassium to exit the cell, thus repolarizing the membrane, and finally, the Na+/K+ pumps restore the resting potential. Sodium channel blockers like TTX specifically inhibit the depolarization phase of the action potential, thereby preventing the neuron from firing.