Question

Studies on the squid giant axon were instrumental in our current understanding of how action potentials are generated. You decide to do an experiment on the squid giant axon yourself. You add NaCl to the extracellular fluid and effectively double the amount of extracellular Na+

cation. How does this affect the action potential?

Answer 1

Doubling the amount of extracellular Na+ by adding NaCl increases the sodium gradient, leading to potentially more rapid depolarization, higher peak voltage of the action potential, and changes in propagation speed, depending on the saturation of sodium channels.

Step-by-step explanation:

When you double the amount of extracellular Na+ cation by adding NaCl, the action potential in a squid giant axon would likely be affected. An increased extracellular Na+ concentration results in a steeper sodium gradient which could lead to more Na+ ions entering the cell during depolarization. This would result in a more rapid depolarization phase, possibly a higher peak voltage of the action potential, and may affect the speed at which the action potentials propagate along the axon. However, this is contingent upon the ability of the voltage-gated sodium channels to accommodate the increased Na+ influx; if they become saturated at normal levels, the actual effect may be less significant. Ultimately, this change functions by altering the difference in concentration of Na+ ions across the cell membrane, thus influencing the electrical difference and the movement of the action potential along the nerve fiber.