Membrane potential

Definition

Membrane potential is the electrical potential difference across a cell's membrane, resulting from the distribution of ions inside and outside the cell. This difference in charge is crucial for various cellular processes, including nerve impulse transmission and muscle contraction. The membrane potential is mainly influenced by the permeability of the membrane to different ions and the activity of ion pumps, which maintain ion gradients.

5 Must Know Facts For Your Next Test

1. Membrane potential is measured in millivolts (mV) and can vary depending on the type of cell and its current state.
2. The sodium-potassium pump is vital for establishing and maintaining resting membrane potential by moving sodium ions out and potassium ions into the cell.
3. Changes in membrane potential are essential for signal transmission in neurons, as they facilitate the generation of action potentials.
4. Different types of cells can have varying membrane potentials, with neurons exhibiting rapid fluctuations due to their specialized functions.
5. The Nernst equation can be used to calculate the equilibrium potential for individual ions, helping to understand how different ions contribute to overall membrane potential.

Review Questions

• How does the distribution of ions across the cell membrane influence the membrane potential?
  • The distribution of ions is crucial for determining the membrane potential because it creates an electrical gradient across the cell membrane. Different concentrations of ions, such as sodium (Na+) and potassium (K+), create a difference in charge. This uneven distribution means that when channels open, ions move according to their concentration gradients, leading to changes in the membrane potential that are vital for processes like nerve signaling and muscle contraction.
• Compare resting potential and action potential in terms of their characteristics and physiological significance.
  • Resting potential is characterized by a stable negative charge inside the neuron at around -70 mV, maintained by ion gradients primarily through the sodium-potassium pump. In contrast, an action potential is a rapid change in this potential that occurs when a neuron is stimulated, resulting in depolarization followed by repolarization. This process is essential for transmitting signals along nerves, highlighting how these two states are integral to neural communication.
• Evaluate how ion channels contribute to changes in membrane potential during synaptic transmission.
  • Ion channels play a crucial role in synaptic transmission by allowing specific ions to flow across the neuronal membrane. When a neurotransmitter binds to receptors on a postsynaptic neuron, it opens ligand-gated ion channels, which can lead to either depolarization or hyperpolarization depending on which ions are allowed to enter or exit. This change in membrane potential influences whether an action potential will be generated, making ion channels fundamental to effective communication between neurons.

Related terms

Resting potential: The membrane potential of a non-active neuron, typically around -70 mV, where the inside of the cell is more negatively charged than the outside.

Action potential: A rapid change in membrane potential that occurs when a neuron is stimulated, leading to a brief reversal of charge across the membrane.

Ion channels: Proteins that span the cell membrane and allow specific ions to flow in and out of the cell, playing a key role in generating and propagating membrane potentials.