What is membrane potential?

• A. Voltage across the cell membrane
• B. Concentration of ions inside the cell
• C. Electrical impulses in the nervous system
• D. Energy produced by muscle contractions

Answer: (A)

Membrane potential refers specifically to the voltage difference across the cell membrane. This voltage is primarily created by the uneven distribution of ions, such as sodium, potassium, chloride, and others, between the inside and outside of the cell. When these ions move across the membrane through various channels and pumps, they contribute to the electrical charge inside the cell compared to the outside environment, which establishes the membrane potential.

Understanding membrane potential is crucial because it plays a vital role in various physiological processes, including the generation of action potentials in neurons and muscle cells, facilitating communication between cells, and regulating cellular activities. The correct answer focuses directly on this fundamental characteristic of cells, distinguishing it clearly from the other options, which relate to different physiological concepts. For example, the concentration of ions inside the cell is a factor that influences membrane potential but does not define it; electrical impulses do not solely represent membrane potential as they result from changes in that potential; and energy from muscle contractions is unrelated to the concept of membrane potential.