Equilibrium potential

Equilibrium potential is a term used in neuroscience and physiology to describe the electrical potential difference across a cell's membrane that is required to counterbalance the diffusive force driving an ion species across that membrane. This concept is fundamental to understanding the ionic currents that underlie nerve impulses.

Overview

The equilibrium potential is determined by the Nernst equation, which takes into account the charge of the ion, the temperature, and the ratio of the external and internal ion concentrations. The equilibrium potential for an ion is the membrane potential at which there is no net (overall) flow of that particular ion from one side of the membrane to the other.

In the context of neurons, the equilibrium potential is often discussed in relation to the resting potential and the action potential. The resting potential is the baseline membrane potential of a neuron, while the action potential is the rapid, temporary change in this potential that occurs in response to stimulation.

Calculation

The equilibrium potential for an ion can be calculated using the Nernst equation:

E = RT/zF ln([X]o/[X]i)

where:

• E is the equilibrium potential
• R is the universal gas constant
• T is the absolute temperature
• z is the charge of the ion
• F is Faraday's constant
• [X]o and [X]i are the outside and inside concentrations of the ion

Role in Neuronal Function

The equilibrium potential plays a crucial role in the generation of the resting and action potentials in neurons. The resting potential is primarily determined by the equilibrium potentials of potassium and sodium, the two main ions involved in neuronal signaling. The action potential, on the other hand, is a result of the temporary deviation from the resting potential caused by the opening and closing of voltage-gated ion channels.

See Also

• Nernst equation
• Resting potential
• Action potential
• Neuron
• Physiology

References

Equilibrium potential Resources
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