Resting membrane potential

Definition

Resting membrane potential refers to the electrical charge difference across the plasma membrane of a cell when it is not actively transmitting signals. This potential is mainly determined by the distribution of ions, particularly sodium (Na+), potassium (K+), chloride (Cl-), and organic anions inside and outside the cell. The resting membrane potential is crucial for maintaining cellular homeostasis and enables cells, especially neurons and muscle cells, to respond rapidly to stimuli by altering their membrane potential.

5 Must Know Facts For Your Next Test

1. The resting membrane potential typically ranges from -60 mV to -70 mV, indicating that the inside of the cell is negatively charged relative to the outside.
2. Potassium ions (K+) play a major role in establishing the resting membrane potential, as there are more potassium channels open at rest compared to sodium channels.
3. The sodium-potassium pump actively transports three sodium ions out of the cell and two potassium ions into the cell, which helps maintain the resting membrane potential.
4. Resting membrane potential is vital for excitability; if it becomes too depolarized or hyperpolarized, it can affect the ability of cells to generate action potentials.
5. Factors such as changes in extracellular ion concentrations or alterations in ion channel function can disrupt the resting membrane potential, impacting cellular function.

Review Questions

• How does the distribution of ions contribute to the establishment of resting membrane potential?
  • The resting membrane potential is primarily established by the uneven distribution of ions across the plasma membrane. Potassium ions (K+) are more concentrated inside the cell while sodium ions (Na+) are more concentrated outside. The selective permeability of the membrane allows K+ to diffuse out more readily than Na+ can enter, leading to a net negative charge inside the cell. This ionic distribution creates an electrochemical gradient that defines the resting membrane potential.
• Discuss how changes in ion channel activity might affect resting membrane potential and cell excitability.
  • Changes in ion channel activity can significantly alter resting membrane potential and influence cell excitability. For example, if sodium channels become more active or open due to a stimulus, more Na+ enters the cell, leading to depolarization and potentially triggering an action potential. Conversely, if potassium channels are activated excessively, K+ may leave the cell rapidly, resulting in hyperpolarization, which makes it harder for the cell to reach threshold for an action potential. These dynamics illustrate how tightly linked ion channel behavior is to cellular signaling.
• Evaluate the significance of resting membrane potential in neural signaling and muscle contraction.
  • Resting membrane potential is crucial for both neural signaling and muscle contraction as it sets the stage for action potentials. In neurons, a stable resting membrane potential allows for rapid changes in voltage when stimulated, facilitating communication between cells. Similarly, in muscle cells, maintaining resting membrane potential enables them to respond effectively to signals from nerves to contract. Disruptions in resting membrane potential can impair these processes, highlighting its fundamental role in ensuring proper cellular function.

Related terms

Action Potential: A rapid and temporary change in the membrane potential of a cell, typically involving depolarization followed by repolarization, leading to signal transmission in neurons and muscle contraction.

Ion Channels: Protein structures in the cell membrane that allow specific ions to pass in and out of the cell, playing a key role in establishing and modifying membrane potentials.

Equilibrium Potential: The electrical potential difference across the membrane that exactly balances the concentration gradient for a particular ion, determining its net movement across the membrane.