What is tonicity?

  • (noun): The elastic tension of living muscles, arteries, etc. that facilitate response to stimuli.
    Example: "The doctor tested my tonicity"
    Synonyms: tonus, tone


Tonicity is a measure of the osmotic pressure gradient (as defined by the water potential of the two solutions) of two solutions separated by a semipermeable membrane. It is commonly used when describing the response of cells immersed in an external solution. Like osmotic pressure, tonicity is influenced only by solutes that cannot cross the membrane, as only these exert an osmotic pressure. Solutes able to freely cross the membrane do not affect tonicity because they will always be in equal concentrations on both sides of the membrane.

Read more about Tonicity.

Some articles on tonicity:

Osmolarity Vs. Tonicity
... Osmolarity and tonicity are related, but different concepts ... the total concentration of penetrating solutes and non-penetrating solutes, whereas tonicity takes into account the total concentration of only non-pene ...
Central Pontine Myelinolysis - Pathophysiology
... be too quick, not allowing enough time for the brain's cells to adjust to the new tonicity ... With a rise in extracellular tonicity, the cells compensate by losing a small amount of water ... If hypertonic therapy continues or is too rapid, the extracellular tonicity will continue to drive water out of the brain's cells, leading to cellular dysfunction and the condition of central pontine myelinolysis ...