Answer to Question #298378 in Human Anatomy and Physiology for Mnare

Question

Discuss the regulation of cell volume

Answer 1

The balance between intracellular osmolarity and extracellular tonicity determines the cell volume. Therefore, changes in cell volume can be initiated by changes in intracellular or extracellular osmolarity and are always associated with the net movement of water through the cell membranes: water exits the cell when the cell shrinks and enters the cell when the cell swells.

After acute swelling, cell volume is regulated by the process of regulatory volume decrease (RVD), which involves the activation of KCl cotransport and of channels mediating K⁺, Cl⁻, and taurine efflux. Conversely, after acute shrinkage, cell volume is regulated by the process of regulatory volume increase (RVI), which is mediated primarily by Na⁺/H⁺ exchange, Na⁺-K⁺-2Cl⁻ cotransport, and Na⁺ channels.

The changes in intracellular osmolarity may occur during the transepithelial secretion or absorption, the accumulation of nutrients and metabolic waste products, and so on. Changes in extracellular tonicity may also occur. For example, intestinal epithelial cells are exposed to low extracellular osmolarity after hypotonic food intake, and renal tubular cells are always exposed to hypertonic extracellular environments to concentrate the urine. Most cells are able to counteract volume perturbations following a shift in intracellular or extracellular osmolarity.