Question

Which of the following correctly explains how you can have several action potentials in a row without

depleting the concentration gradients of K+ and Na+?
a. Although an action potential strongly affects the concentration gradients of K+ and Na+, the Na/K
pump rapidly restores the gradients.
b. Electrical gradients cause K+ and Na+ to reverse their flow after an action potential, which quickly
restores the membrane to its resting state.
c. Although an action potential proceeds along an entire axon, it is able to recycle the same K+ and
Na+ ions as the action potential proceeds, such that there is no net change in the ion gradients.
d. Both Na+ and K+ gradients are restored during the hyperpolarization phase of an action potential.
e. Although there are large changes in localized membrane voltages, the ions that cross the
membrane are only a very small proportion of all the ions in the intracellular and
extracellular solutions.

Answer 1

Action potentials can occur in succession without depleting the Na+ and K+ gradients because only a small fraction of ions are involved in each action potential, and the Na+/K+ pump actively maintains the gradients over the long term.

Step-by-step explanation:

The question pertains to how action potentials can occur in succession without depleting the ion concentration gradients of sodium (Na+) and potassium (K+). The correct answer involves understanding that during an action potential, only a small fraction of ions move across the cell membrane. This means that the sheer number of Na+ and K+ ions present inside and outside the cell is so great that the few ions that do move do not significantly alter the overall concentration gradients. The Na+/K+ pump, which is powered by ATP, works to maintain these gradients over the long term by moving ions against their concentration gradients, ensuring that the cell can fire many action potentials in rapid succession without depletion.