The Goldman equation expands on the principles established by the Nernst equation by considering multiple ions simultaneously, rather than focusing on a single ion’s concentration gradient. While the Nernst equation calculates the equilibrium potential for one specific ion based on its concentration difference across a membrane, the Goldman equation incorporates several important factors:
- Multiple Ions: The Goldman equation takes into account the permeability and concentration of multiple ions (typically sodium, potassium, and chloride) across the membrane. This provides a more comprehensive picture of the membrane potential.
- Relative Permeability: It weights the contribution of each ion to the membrane potential based on its relative permeability. For example, if a membrane is more permeable to potassium than sodium, this difference is reflected in the calculated resting membrane potential.
- Ion Concentrations: The equation considers the extracellular and intracellular concentrations of multiple ions, which are crucial for accurately determining the resting and action potentials in excitable cells like neurons and muscle cells.
In summary, while the Nernst equation provides valuable insight into individual ion behavior, the Goldman equation gives a fuller view of the electrical potential by factoring in the effects of multiple ions and their respective permeabilities.