Resting membrane potential in nerve is-
**Core Concept**
The resting membrane potential in nerve cells is a result of the diffusion of ions across the cell membrane, creating a negative electrical charge inside the cell. This is primarily due to the selective permeability of the cell membrane to potassium ions (K+), which are more abundant inside the cell, and the presence of an electrogenic pump, the Na+/K+-ATPase, that maintains the concentration gradients of sodium (Na+) and potassium ions.
**Why the Correct Answer is Right**
The resting membrane potential is generated by the movement of potassium ions out of the cell through potassium leak channels, which are open at rest. As potassium ions leave the cell, they carry a positive charge with them, leaving the inside of the cell with a net negative charge. The sodium-potassium pump (Na+/K+-ATPase) also plays a crucial role in maintaining the concentration gradients of sodium and potassium ions across the cell membrane, which in turn affects the resting membrane potential.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the resting membrane potential. While the sodium-potassium pump does play a role in maintaining the concentration gradients of sodium and potassium ions, it is not the primary mechanism responsible for generating the resting membrane potential.
**Option B:** This option is incorrect because it is not a specific enough description of the resting membrane potential. While the cell membrane is selectively permeable, this option does not accurately describe the specific ion movements that occur at rest.
**Option C:** This option is incorrect because it is not a valid description of the resting membrane potential. The resting membrane potential is not a result of the movement of chloride ions, but rather the movement of potassium ions.
**Clinical Pearl / High-Yield Fact**
The resting membrane potential is an important concept in understanding how nerve cells function, and it has implications for the treatment of various neurological disorders, such as epilepsy and multiple sclerosis. Understanding the mechanisms that generate the resting membrane potential can also inform the development of new treatments for these conditions.
**Correct Answer: D. 85mV**