What does a solution called 'isotonic' mean?

An isotonic solution is one that has equal solute concentration to that inside a cell. This balance is crucial for maintaining homeostasis and ensures that there is no net movement of water into or out of the cell. When a cell is placed in an isotonic solution, the osmotic pressure is equal, allowing the cell to maintain its shape and function effectively. This is particularly important in physiological contexts, such as during intravenous fluid administration, where it is essential to avoid cell shrinkage or swelling.

In comparison, solutions with higher or lower solute concentrations than that of the cell would lead to osmotic pressures that could result in the swelling or shrinking of the cell, disrupting its normal functions. Thus, the concept of isotonicity is vital in nursing and healthcare in understanding fluid balance and cellular health.