2.3.4: Resting Membrane Potential — Read

From LibreTexts, under CC BY-NC-SA 4.0, as the source states it; its equations are written in TeX, which the PDF shows typeset. This page at LibreTexts.

The membrane potential signifies the spatial allocation of electrical charge spanning the cell membrane, quantified in millivolts (mV). Conventionally, the reference point entails evaluating the interior of the cell relative to its external surroundings. Therefore, the membrane potential is a numerical manifestation characterizing the charge amassed within the intracellular domain of the membrane. The concept of the resting membrane potential encapsulates the equilibrium state of the cell, an incessantly active process counterbalanced by ion diffusion and active ion transport. Without external influences, the membrane potential persists in an unchanging state.

Graded Potentials

Localized alterations in the membrane potential are denoted as graded potentials, predominantly manifesting within the dendritic domains of neurons. The extent of variation in the membrane potential is contingent upon the magnitude of the inciting stimulus. In the example of shower temperature, tepid water would illustrate a minor shift in the membrane potential of a thermoreceptor. In contrast, elevated temperature would substantially increase the membrane potential.

Graph depicting membrane potential changes with hypo- and depolarizing stimuli. Shows hyperpolarizing graded potential, depolarizing graded potential, and action potential spikes. — Figure 9 | Graded Potentials | This schematic diagram illustrates changes in the membrane potential of a neuron in response to stimuli. Graded potentials are localized variations in membrane potential that can either depolarize (depicted by the upward shift) or hyperpolarize (depicted by the downward shift) the neuron. An influx of positive ions causes a transient depolarization, which results in a shift towards a less negative membrane potential. Conversely, an efflux of positive ions or an influx of negative ions causes a temporary hyperpolarization, making the membrane potential more negative than the resting state. These graded potentials play a crucial role in influencing the generation of action potentials.

Graded potentials encompass a duality characterized by their depolarizing or hyperpolarizing nature, as depicted in Figure 9. Depolarizing graded potentials often arise due to the selective influx of sodium or calcium ions through specific ion channels. These ions possess higher extracellular concentrations compared to the intracellular environment. Their positive charge makes them migrate into the cell, reducing the intracellular negativity relative to the extracellular milieu. Conversely, hyperpolarizing graded potentials are caused by the efflux of potassium ions from the cell or the influx of chloride ions into the cell, facilitated by activating corresponding ion channels. The cellular environment becomes more negative when negative charges such as chloride ions enter the cell or when positive charges, such as potassium ions, exit the cell. The sodium-potassium exchange pumps are employed to restore the membrane potential to its resting state unless subsequent stimuli persist in driving the potential toward either depolarization or hyperpolarization. This reversal of the graded potential to its original state is referred to as repolarization. Furthermore, the amplitude of the graded potential gradually wanes as it propagates away from its initial active site, yielding a decremental pattern over distance.¹²

During cellular quiescence, ions distribute across the membrane in a highly anticipated manner when ion channels remain closed (except for leakage channels, which exhibit sporadic activation; Figure 10). The extracellular compartment hosts a sodium concentration approximately tenfold that of the intracellular milieu, while the intracellular environment holds a heightened potassium ion concentration relative to the extracellular surroundings. The cytosol is enriched with abundant anions, primarily as phosphate ions and negatively charged proteins. The intracellular portion of the membrane is characterized by sizable anionic entities encompassing specialized phospholipids and proteins. Given such distribution of ions within the membrane, a disparity in charge emerges, quantified at -70 mV, denoting the established resting membrane potential. Although the precise measurement of the resting membrane potential may vary among different cell types, the standard benchmark of -70 mV is widely adopted. Leakage channels facilitate a gradual influx of sodium or efflux of potassium ions across the cell membrane while the sodium-potassium exchange pump endeavors to reinstate their original concentrations.¹³

Diagram illustrating ion movement across a cell membrane via an Na+/K+ pump, Ca2+ channel, and K+ channel, with labeled ions and a voltage meter indicating potential difference. — Figure 10 | Schematic Representation of Ion Distribution and Resting Membrane Potential during Cellular Quiescence | ¹⁴ The diagram illustrates the distribution of ions across the cell membrane during a quiescent state. The extracellular compartment exhibits a tenfold higher sodium ion (\(\ce{Na+}\)) concentration compared to the intracellular milieu, while the intracellular environment maintains an elevated potassium ion (\(\ce{K+}\)) concentration. The intracellular membrane features sizable anionic entities. The resulting charge disparity establishes a resting membrane potential of -70 mV, a standard benchmark across cell types. At resting membrane potential, voltage-gated \(\ce{Na+}\) and \(\ce{K+}\) channels are closed and \(\ce{Na+}\)/\(\ce{K+}\) pump maintains normal concentrations of \(\ce{Na+}\) and \(\ce{K+}\).

This page titled 2.3.4: Resting Membrane Potential was last modified on Sat, 22 Aug 2026 03:00:13 GMT and is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by Chaya Gopalan (Consortium of Academic and Research Libraries in Illinois (CARLI)) .

Contents

Text

Graded Potentials