Resting membrane potential

Definition

Resting membrane potential is the electrical potential difference across the plasma membrane of a cell when it is not actively transmitting signals, typically around -70 mV in neurons. This state is crucial for maintaining cellular homeostasis and enabling the excitability of cells, particularly in neurons and muscle cells, facilitating the transport of ions and the initiation of action potentials.

5 Must Know Facts For Your Next Test

1. Resting membrane potential is primarily determined by the distribution of potassium (K+) and sodium (Na+) ions across the cell membrane, with K+ being more concentrated inside the cell.
2. The sodium-potassium pump (Na+/K+ ATPase) actively transports 3 Na+ ions out of the cell and 2 K+ ions into the cell, which is essential for maintaining resting membrane potential.
3. The permeability of the cell membrane to different ions also contributes to resting membrane potential; it is more permeable to K+ than Na+ at rest.
4. Changes in resting membrane potential can result from alterations in ion concentrations or channel activity, which can influence excitability and signal transmission in cells.
5. Resting membrane potential is critical for normal cellular functions, including muscle contraction, neurotransmitter release, and the overall communication between cells.

Review Questions

• How does the distribution of ions across the cell membrane contribute to resting membrane potential?
  • The distribution of ions, particularly potassium (K+) and sodium (Na+), plays a key role in establishing resting membrane potential. K+ is more concentrated inside the cell, while Na+ is more abundant outside. The difference in concentration creates a gradient that influences the movement of these ions through ion channels. Since the cell membrane is more permeable to K+ than Na+, K+ tends to leak out of the cell, resulting in a negative charge inside relative to the outside, thus contributing to resting membrane potential.
• Discuss how changes in resting membrane potential can affect neuronal excitability.
  • Changes in resting membrane potential can significantly impact neuronal excitability by altering how easily a neuron can reach the threshold for action potentials. If the resting membrane potential becomes less negative (depolarization), neurons may become more excitable and fire action potentials more readily. Conversely, if it becomes more negative (hyperpolarization), excitability decreases, making it harder for neurons to fire. These changes can result from variations in ion channel activity or alterations in ion concentrations within the cell's environment.
• Evaluate how the sodium-potassium pump contributes to resting membrane potential and discuss its broader implications for cellular function.
  • The sodium-potassium pump (Na+/K+ ATPase) is crucial for maintaining resting membrane potential by actively transporting 3 Na+ ions out of the cell and 2 K+ ions into it. This active transport creates and maintains concentration gradients essential for normal cellular functions. The pump not only helps stabilize resting membrane potential but also prepares cells for action potentials and muscle contractions. A malfunction in this pump could lead to severe disruptions in electrical signaling, impacting everything from nerve impulses to heartbeats.

Related terms

action potential: A rapid, temporary change in the membrane potential of a cell that occurs when a threshold is reached, allowing for the transmission of electrical signals along neurons.

ion channels:

Proteins that span the cell membrane, allowing specific ions to flow in and out of the cell, playing a key role in establishing and maintaining resting membrane potential.

Nernst equation: A mathematical formula used to calculate the equilibrium potential for a specific ion across a membrane, helping to explain how resting membrane potential is established.