Isotónískum

Isotónískum refers to a state where a solution has the same osmotic pressure as another solution, typically a biological fluid. In biological contexts, an isotonic solution is one that has the same concentration of solutes as the cytoplasm of a cell. When a cell is placed in an isotonic solution, there is no net movement of water across the cell membrane. This is because the rate at which water enters the cell is equal to the rate at which water leaves the cell.

The concept of isotonicity is crucial in medicine, particularly in the administration of intravenous fluids. For example, normal saline, which is a 0.9% sodium chloride solution, is considered isotonic with human blood plasma. This means that when administered, it does not cause red blood cells to swell or shrink. Other isotonic solutions used clinically include lactated Ringer's solution.

Understanding isotonicity is also important in physiology and cell biology. If a cell is placed in a hypotonic solution (one with a lower solute concentration than the cytoplasm), water will move into the cell, causing it to swell and potentially burst (lysis). Conversely, if a cell is placed in a hypertonic solution (one with a higher solute concentration than the cytoplasm), water will move out of the cell, causing it to shrink (crenation). Therefore, maintaining isotonic conditions is vital for cellular integrity and function.