Osmoregulation – Class 11 | Chapter – 19 | Biology Short Notes Series PDF

Osmoregulation is a function of our body that controls the fluid’s osmotic pressure and the balance of electrolytes in our body. Osmoreceptors that detect the changes in osmotic pressure are used for this process in animals. These Osmoreceptors can be found in most warm-blooded organisms including humans, in their hypothalamus. These osmoregulators are not only found not only in the brain but in the kidneys as well. There are two major kinds of Osmoregulators. These are osmoconformers and osmoregulators namely. The difference is while the former regulates the osmotic pressure of the body according to its surroundings, the latter is independent of its surroundings. Different animals show osmoregulation in their body differently, like fishes, BacteriaPlants, Animals and Humans, all have different systems of Osmoregulation.

Types of Osmoregulation

Osmoregulation can be classified into two major kinds:

  • Osmoconformers

Osmoconformers are the kind of organisms that match their body’s osmolarity according to their surroundings. They tend to keep the osmotic pressure consistent throughout the body as the same as the outside water. They conform through passive or active means. Most of the invertebrates that are marines, such as jellyfish, lobsters and starfish are osmoconformers.

  • Osmoregulators

Osmoregulators are the type of organisms that are actively maintaining their osmotic pressure, regardless of the environment surrounding them, as they are independent. Many vertebrates, such as humans, are osmoregulatory, the same as most freshwater fishes, whose gills keep up taking salt from the surroundings by using mitochondria-rich cells. Water diffuses into the fishes, excreting dilute urine that expels all extra water.

Osmoregulation in Plants

Stomata that is present under the leaves is used to control water loss. Plants that grow in well-hydrated soils use transpiration to compensate for water loss as they keep absorbing extra water from the soil. Plants that are grown in semi-arid areas use their vacuoles to store water. They also tend to have fleshy and thick cuticles which helps to prevent water loss. A hormone called Abscisic Acid helps to close the stomata and to increase the intake of water from the roots, so it is vital for conserving water for plants.

Osmoregulation in Fish

Marine fish and Freshwater fish use different ways to osmoregulate. The environment surrounding them has different salinity levels and so does the process of osmoregulation.

  • Osmoregulation in Freshwater Fish

The fishes in Freshwater are hypertonic to their surroundings, so the salt concentration is higher in their blood than in their surroundings. They tend to take in a controlled amount of water with the help of their mouth and the gills. This large intake of water causes them to produce lots of urine, which helps in losing excess salt. The salt gets removed by using the mitochondria in the rich cells of the gills. These cells are used to take the salt into the blood from its surroundings.

  • Osmoregulation in Marine Fish

Marine fishes go through the opposite of what freshwater fishes go through. The concentration of water in their blood is higher than their surroundings. This results in it losing water and absorbing salt. But to counter this difficulty, the marine fishes drink large amounts of water and limit urination. They also continuously expel salt from the body using the gills, and this costs them a lot of their energy.

Osmoregulation in Animals

Animals use their developed excretory system to regulate the loss of water from the body. This helps them to maintain the osmotic pressure.

Osmoregulation in Humans

Kidneys are the organs responsible for the handling of osmoregulation in human beings. Amino acidsglucose and Water are reabsorbed by the kidneys. The body releases a vast amount of urine that is hypotonic when the water level in the body is high. However, it keeps water and makes less amount of hypertonic urine when the water level is low. This helps the kidneys to maintain an electrolytic balance.

Angiotensin II, Antidiuretic hormones and Aldosterone are the ones responsible for controlling the absorption process in our body. Perspiration causes the loss of some water and electrolytes.

Osmoreceptors present in the hypothalamus region of the brain are responsible for controlling our thirst and the production of ADH. ADH is responsible for opening the water channels of aquaporins that allows the water to flow. Thus, As long as the pituitary gland keeps releasing ADH, the kidneys will keep absorbing water.

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By Team Learning Mantras