Osmoregulation is a complex process utilized by living organisms to ensure that their osmotic pressure remains stable. There are a number of different types of osmoregulation, and a wide variety of techniques can be used to regulate osmotic pressure in everything from plants to whales. In all cases, the goal is to keep the consistency and level of body fluids constant.
Osmoconformers attempt to conform to their surrounding environment. This type of osmoregulation is seen most commonly in marine invertebrates. In these animals, the consistency of the body fluids matches that of the surrounding water, so there is no net gain or loss of water or salts from the body of the fish. Osmoregulators, on the other hand, maintain a very strict osmotic pressure which does not conform with the surrounding environment, and this type of osmoregulation is the most common.
Osmotic pressure involves the tendency for a solution of lower concentration to flow across a membrane to a solution of higher concentration. Inside the body, it is critical to regulate osmotic pressure to achieve what is known as an isotonic solution, meaning that there is no net gain or loss of fluids and salts in a cell, but instead a steady flow in and out. If the body fluids around the cell are too diluted, water flows into the cell, causing it to swell and potentially burst. In contrast, if the body fluids around a cell are concentrated, water flows out of the cell, causing it to wither.
Metabolic processes are used to remove wastes from the body and to keep the levels of dissolved salts and other compounds in the blood stable. This ensures that the cells of the body are bathed in an isotonic solution which will maintain cell health. Most organisms need to consume water to maintain osmoregulation, as the water can be used to dilute the body fluids if they become too concentrated, or it can be excreted if it is not needed.
In a classic example of osmoregulation at work, when people drink, the alcohol acts as a diuretic, forcing the body to excrete water, and concentrating the salts in the body fluids, creating a hypertonic solution. As a result, the cells experience a net loss of water, and the body develops what is known as a “hangover.” By drinking lots of water while drinking alcohol, people can help their bodies maintain osmoregulation, decreasing the risk of a hangover by keeping the body fluids isotonic.