Membrane potential

Definition

Membrane potential refers to the difference in electric charge across a cell's plasma membrane, primarily caused by the distribution of ions such as sodium, potassium, and chloride. This electric gradient is crucial for various cellular processes, including signal transmission in neurons and muscle contractions. It creates a resting state that cells maintain, allowing them to respond to stimuli effectively.

5 Must Know Facts For Your Next Test

1. Membrane potential is measured in millivolts (mV) and indicates whether the inside of the cell is more positive or negative relative to the outside.
2. The sodium-potassium pump actively transports sodium out of the cell and potassium into the cell, contributing to the resting membrane potential.
3. Changes in membrane potential are essential for processes like synaptic transmission, muscle contraction, and other forms of cellular communication.
4. When the membrane potential reaches a certain threshold during depolarization, it can trigger an action potential, leading to nerve impulses.
5. In excitable cells like neurons and muscle fibers, rapid changes in membrane potential enable quick responses to environmental changes or stimuli.

Review Questions

• How does the resting membrane potential contribute to a cell's ability to respond to stimuli?
  • The resting membrane potential creates an electric gradient that allows cells to remain in a state ready for action. When a stimulus occurs, ion channels open, causing changes in the membrane potential that can lead to action potentials. This readiness is critical for neurons to transmit signals and for muscle cells to contract effectively.
• Describe the process of how an action potential is generated in relation to membrane potential changes.
  • An action potential is generated when a neuron's membrane potential depolarizes past a specific threshold due to the opening of voltage-gated sodium channels. Sodium ions rush into the cell, causing rapid depolarization. Following this, potassium channels open to repolarize the membrane by allowing potassium ions to exit, restoring the resting membrane potential and preparing the neuron for another signal.
• Evaluate the impact of ion channels on maintaining and altering membrane potential during cellular signaling.
  • Ion channels play a pivotal role in maintaining and altering membrane potential by regulating the flow of specific ions across the cell membrane. The opening and closing of these channels can create localized changes in membrane potential, which are essential for generating action potentials. A malfunction in these channels can disrupt cellular signaling pathways, affecting overall cellular function and communication within tissues.

Related terms

resting membrane potential: The voltage difference across the membrane of a non-excited cell, typically around -70 mV, created mainly by the unequal distribution of ions.

action potential: A rapid change in membrane potential that occurs when a neuron or muscle cell becomes excited, resulting in the transmission of an electrical signal.

ion channels: Proteins embedded in the cell membrane that allow specific ions to pass through, playing a key role in establishing and changing membrane potential.