Membrane Potential

The membrane potential is the difference in electric potential between the interior and the exterior of a cell, specifically a neuron or a muscle cell. It is a key concept in understanding the function of these cells in the nervous and muscular systems.

Causes of Membrane Potential

The membrane potential is primarily caused by the uneven distribution of ions across the cell membrane. The main ions involved are sodium (Na+), potassium (K+), chloride (Cl-), and large negatively charged proteins. The selective permeability of the cell membrane and the action of ion channels and pumps maintain this unequal distribution of ions.

Resting Membrane Potential

When a cell is at rest, meaning it is not actively sending signals, it has a resting membrane potential. In neurons, this is typically around -70 millivolts (mV). This negative value indicates that the interior of the cell is more negative compared to the exterior.

Action Potentials

Changes in the membrane potential, such as depolarization (when the potential becomes less negative) and hyperpolarization (when the potential becomes more negative), are involved in the generation and propagation of action potentials, which are the electrical signals that allow neurons to communicate with each other.

Functions of Membrane Potential

The membrane potential is critical for various cellular functions, including the transmission of nerve impulses, muscle contraction, and the maintenance of cell volume. It also plays a role in regulating the movement of substances into and out of the cell.

Study Guide

1. What is membrane potential?
2. What are the main ions involved in creating membrane potential?
3. What is the typical resting membrane potential in neurons?
4. How do changes in membrane potential contribute to the generation of action potentials?
5. What are the functions of membrane potential in cells?

Understanding the concept of membrane potential is essential for grasping the functioning of neurons and muscle cells, and it forms the basis for studying topics such as nerve conduction, synaptic transmission, and muscle physiology.