Resting membrane potential in nerve fibre
**Core Concept**
The resting membrane potential in nerve fibers is a stable electrical potential difference across the cell membrane, generated by the uneven distribution of ions (sodium and potassium) across the membrane and their movement through ion channels. This potential difference is essential for the transmission of nerve impulses.
**Why the Correct Answer is Right**
The resting membrane potential is primarily maintained by the potassium-sodium pump (Na+/K+-ATPase) and the selective permeability of the membrane to potassium ions (K+). The high concentration of potassium ions inside the cell and the low concentration outside the cell lead to a net outward flow of K+ ions through potassium leak channels (K+ channels), which is counteracted by the sodium-potassium pump. This balance of ion movements results in a negative resting membrane potential, typically around -70 mV.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify the role of ion channels or the ion pump in maintaining the resting membrane potential.
**Option B:** This option is incorrect because it implies that the resting membrane potential is solely due to the movement of sodium ions (Na+), which is not accurate.
**Option C:** This option is incorrect because it mentions an "ion channel" without specifying the type of ion (K+ or Na+) or the direction of ion flow.
**Clinical Pearl / High-Yield Fact**
The resting membrane potential is a critical parameter for understanding nerve conduction and can be altered by various factors, including changes in ion concentrations, membrane permeability, or the presence of toxins.
**Correct Answer: A. The resting membrane potential is primarily maintained by the potassium-sodium pump (Na+/K+-ATPase) and the selective permeability of the membrane to potassium ions (K+).**