Action potential across cell membrane is maintained by?
**Core Concept**
Action potentials are rapid changes in membrane potential that occur in excitable cells, such as neurons and muscle cells. The maintenance of action potential is essential for the transmission of electrical signals across the cell membrane.
**Why the Correct Answer is Right**
The maintenance of action potential is primarily due to the selective permeability of the cell membrane to ions, particularly sodium (Na+) and potassium (K+). During the action potential, voltage-gated sodium channels open, allowing an influx of Na+ ions into the cell, which depolarizes the membrane. This is followed by the closure of sodium channels and the opening of voltage-gated potassium channels, allowing an efflux of K+ ions from the cell, which repolarizes the membrane. The action potential is maintained due to the rapid reuptake of Na+ ions by the sodium-potassium pump (Na+/K+-ATPase) and the selective permeability of the cell membrane.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the mechanism by which action potentials are maintained.
**Option B:** This option is incorrect because it is not directly related to the maintenance of action potential.
**Option C:** This option is incorrect because while calcium ions do play a role in the regulation of certain cellular processes, they are not primarily responsible for maintaining action potential.
**Clinical Pearl / High-Yield Fact**
It is essential to remember that the maintenance of action potential is a critical process in the transmission of electrical signals across the cell membrane. Disruptions to this process can lead to various neurological and muscular disorders.
**Correct Answer: D. The rapid reuptake of Na+ ions by the sodium-potassium pump (Na+/K+-ATPase) and the selective permeability of the cell membrane.**