## **Core Concept**
The resting membrane potential (RMP) is the difference in electrical charge between the inside and outside of a cell when the cell is at rest. In ventricular myocardium, this potential is primarily determined by the distribution and permeability of ions (mainly potassium, sodium, and to a lesser extent, chloride) across the cell membrane. The RMP is crucial for the proper functioning of cardiac cells, including the generation and propagation of action potentials.

## **Why the Correct Answer is Right**
The resting membrane potential in ventricular myocardium is approximately **-80 to -90 mV**. This value is largely determined by the high permeability of the cardiac cell membrane to potassium ions (K+) at rest, due to the presence of various potassium channels, and the action of the **sodium-potassium ATPase pump**. The pump helps maintain the concentration gradients for sodium (Na+) and potassium (K+) across the membrane, with higher concentrations of K+ inside the cell and higher concentrations of Na+ outside the cell. The outward flow of K+ ions leaves the inside of the cell more negatively charged compared to the outside.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because the value provided does not accurately represent the resting membrane potential in ventricular myocardium.
- **Option B:** This option is incorrect because, similar to option A, the provided value does not match the established range for the resting membrane potential in ventricular myocardial cells.
- **Option D:** This option is incorrect as it suggests a positive value for the resting membrane potential, which contradicts the fundamental physiological principle that the resting membrane potential is negative.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the resting membrane potential is critical for the initiation and propagation of the action potential in cardiac cells. Alterations in RMP, such as those caused by changes in electrolyte concentrations (e.g., hypokalemia, hyperkalemia) or certain drugs, can affect cardiac excitability and contractility. For example, **hypokalemia** can decrease the resting membrane potential (make it less negative), potentially leading to increased excitability and the risk of arrhythmias.

## **Correct Answer:** . -85 mV