Osmoregulation is the process, by which the body adjusts to a change in an environment of different water volume and amount of solutes in a cells and body fluid of organisms including vertebrates. Vertebrates are animals, which have a backbone, and can be warm either blooded or cold blooded. The body of such organisms adjusts in order to maintain the body balance both inside and outside their bodies in mild and harsh environments ranging from seawater, fresh water, and terrestrial habitats to very hostile environments. Endocrine glands found in such organisms play a major role in constant and persistent regulation of body balance, which secretes hormones directly into the blood whenever the body witnesses any environmental change (Bentley 45).
Endocrine glands present in vertebrates play a major role in controlling the level of water and salt in vertebrate's bodies. Hormones produced in vertebrates play a major role in controlling the homeostasis processes in the bodies. Prolactin, neurohypophisicaloctapeptides and adrenocortical steroids are the major hormones in osmotic body balance, in vertebrates. Prolactin acts on osmoregulatory organs such as gills, skins, intestines, urinary bladder and salt glands to control the water and ions present in the vertebrates. Neurohypophisical hormone (ADH) aids in the permeability of skins, renal tubules in kidneys and urinary bladder of vertebrates, which rely on such organs for osmoregulation. ADH also alters blood pressure of vertebrates depending on the change of environment for the vertebrates to fit in the environment. Adrenocortical steroid hormone also plays a major role in controlling electrolytes present in the bodies of vertebrates. Its major purpose is to increase the re-absorption of sodium ions back to the body system and excrete potassium ions. It reduces loss of sodium ions and aids in excretion of potassium ions via organs such as sweat glands, salivary glands and the intestines.
Cold-blooded vertebrates react to stimuli depending on the type of the environment, either salty or fresh water. Whenever the vertebrate detects any change of environment, the body reacts to the stimuli and hormones are produced to regulate the body balance. The glands detect the change in blood plasma concentration, and hence stimulated to produce specific hormones to respond to change. Either the receptor nerves found on the cell membrane or cell nucleus sends an impulse to regulatory hormones, endocrine, via the body tissues. The hormones hence produced depending on the environment to regulate the water present in the body of such vertebrates, and reacts differently with different environments. The hormone is under regulation of prolactin and cortisol, which regulate the Sodium ions and arginine vasotocin (AVT) which is responsible for water control, and can give either positive feedback or negative feedback towards the stimuli. Negative feedback is always the major stimuli produced by endocrines, for both terrestrial and aquatic animals.
Terrestrial animals live dominantly on land while aquatic animals live dominantly in water. Aqua- terrestrial animals live both in land and in water like frogs. Humans are terrestrial animals; humans use different mechanisms to regulate the water balance in the body. For the normal functioning of human cells, there has to be a balance in the osmotic pressure. Homeostasis is the process of diffusion and osmosis, which balance the body fluids. There are kidneys, which remove waste products after purifying them from the blood. The kidneys have different adaptations including the long nephrons, which help in regulation of salts with control from hormones.
The endocrine glands are used in the regulation of salt in the body. These glands control metabolic processes like chemical reactions, regulate the concentration of water in the body and transport substances through membranes. There are many endocrine glands and pituitary glands. Thyroid and adrenals are the ones mostly used in osmoregulation.
In human beings, this balance is maintained by the control of input and output of water in the body. In incidence where water levels reduce in the body, kidneys excrete a small amount of concentrated water so that water is conserved. When there is a lot of water in the body, the kidney excretes a lot of water, which is diluted. This happens when sodium levels rise and cells signal pituitary gland in producing ADH hormone. This hormone signals the kidney to retain water hence diluting the levels of sodium. Kidneys sensors can detect when there is a decrease in blood pressure this trigger a process that is complex and eventually triggers adrenal glands to release aldosterone hormone. This hormone signals the kidney to retain sodium. When sodium is retained, water flows to avoid concentration of sodium. ADH helps in reabsorption of water in the kidney, while aldosterone triggers reabsorption of water and sodium. Angiotensin hormone triggers the production of aldosterone, which in turn triggers the maintenance of water. Aldosterone, in the corporation of vasopressin, helps in maintenance of blood pressure. Kidneys aids in the absorption of water and required minerals in the body under the influence of hormones via the kidney nephrons and the required sodium level is also re-absorbed in the kidney (Rhoades & Bell 432).
Kidneys aids in the control of the body blood pressure in all living animals and for cellular processes, it controls the salt levels. Gastrointestinal absorption of ions such as calcium is also aided in the kidney following the activated vitamin D in the kidney. Kidneys minimize the viscosity of blood in human beings, by controlling the amount of red blood cells produced in red bone marrow, triggered by the hormone erythropoietin. Oxygen is hence controlled by the kidney, as it enhances the control of red blood cell production.
Amphibians are examples of aqua-terrestrial vertebrates. Most of the frogs do not live in salty water because most amphibians find it hard to deal with salty water. This is because salty water can diffuse in their skin causing them to dehydrate. The only frog capable in living in salty environments is the crab-eating frog. It does not excrete urea as a waste product but retains it to make its ionic level higher. This regulates the amount of water diffusing through the skin hence avoid dehydration. In frogs, pituitary glands hormones affect how permeable their membranes are in water. Water uptake by the bladder is influenced when influenced by the oxytocin hormone. Dorsal and ventral skins help amphibians in regulation of water and sodium ions in amphibians, triggered by the prolactin hormone. Prolactin receptor in amphibians is found on their epidermal layer of their skin, dorsal and ventral, and highly concentrated and effective on the dorsal skin. Pituitary gland synthesizes the prolactin, which triggers the skin of amphibians react towards the change of environment and makes the skin permeable to water to regulate osmotic pressure.
There are three organs involved in regulation of salt in frogs. These are urinary bladder, kidney and skin. A single hormone is used to serve the physiological purpose of water control. Arginine Vasotocin is used to inject to the amphibians, and it shows antideuresis. Levels of vasotocin show that hypovalemia is the potential stimulator for the release of neurohypophysis hormone. This hormone helps to control sodium across the skin and its reabsorption in the blood. This hormone is not very significant as it is seen mostly in bullfrogs. Aldosterone has more effects in transport of sodium across the skin and its control in the urinary bladder. This aldosterone is released by the renin angiotensin system, and corticosterone. Vasopressin and vasotocin limits the excretion of water via the three organs whenever the water concentration is lower than the salt present in the amphibians. Amphibians also use the prolactin hormone in the regulation of electrolyte balance and water.
Fish is an example of aquatic vertebrate. Fish can take in and remove water to achieve an osmotically free environment in their bodies. They migrate from areas of high salinity to low salinity. This requires different osmoregulatory mechanisms. These processes can sometimes be modulated by hormones. Movement from different environments changes the concentration of solutions in their bodies as a result of diffusion of different salts. This change in concentration requires adjustments to the concentration of solutes. Neurohypophysial and adrenocortical membranes are the hormones responsible for water and salt regulation in most tetrapod vertebrate and amphibians. The two hormones regulate the solutes via their epithelial membrane. Fish regulate water and salt via their opercula membrane and gills where water and salt diffuse freely.
The excreting tissues contain salt-secreting chloride cells controlled by hormones, which aid in the diffusion of sodium ions against the diffusion gradients and enables the fish to survive in salty water. Euryhaline-teleost is a hormone responsible for the control of salt concentration in both salty and fresh water. While in fresh water, euryhaline-teleost hormone triggers the gills and their membrane to be hypertonic in water and hence continuous diffusion into the blood stream. Kidneys also play a significant role in controlling water intake in fish in fresh water, as they excrete dilute urine that also consist some amount of salt that aid in regulating the osmotic balance. Corpuscels of stannnius is…