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Osmoregulation is the active regulation of the osmotic pressure of an organism's body fluids, detected by osmoreceptors, to maintain the homeostasis of the organism's water content; that is, it maintains the fluid balance and the concentration of electrolytes (salts in solution which in this case is represented by body fluid) to keep the body fluids from becoming too diluted or concentrated.
An osmoreceptor is a sensory receptor primarily found in the hypothalamus of most homeothermic organisms that detects changes in osmotic pressure.Osmoreceptors can be found in several structures, including two of the circumventricular organs – the vascular organ of the lamina terminalis, and the subfornical organ.
At an evolutionary level, this stabilization of oxygen levels, which also results in a more constant carbon dioxide concentration and pH, was important to manage oxygen flow in air-vs.-water breathing, sleep, and to maintain an ideal pH for protein structure, since fluctuations in pH can denature a cell's enzymes.
Blood levels of oxygen become important in hypoxia. These levels are sensed by central chemoreceptors on the surface of the medulla oblongata for decreased pH (indirectly from the increase of carbon dioxide in cerebrospinal fluid ), and the peripheral chemoreceptors in the arterial blood for oxygen and carbon dioxide.
The kidneys measure the oxygen content rather than the partial pressure of oxygen in the arterial blood. When the oxygen content of the blood is chronically low, oxygen-sensitive cells secrete erythropoietin (EPO) into the blood. [53] The effector tissue is the red bone marrow which produces red blood cells (RBCs, also called erythrocytes).
The aortic bodies measure partial gas pressures and the composition of arterial blood flowing past it. [7] These changes may include: oxygen partial pressure. [7] [8] carbon dioxide partial pressure. [7] [8] pH (indirectly affected by carbon dioxide concentration). [1] [8] They are particularly sensitive to changes in pH. [2]
Oxygen saturation is the fraction of oxygen-saturated haemoglobin relative to total haemoglobin (unsaturated + saturated) in the blood. The human body requires and regulates a very precise and specific balance of oxygen in the blood. Normal arterial blood oxygen saturation levels in humans are 96–100 percent. [1] If the level is below 90 ...
Homeostasis regulates, among others, the pH, sodium, potassium, and calcium concentrations in the ECF. The volume of body fluid, blood glucose, oxygen, and carbon dioxide levels are also tightly homeostatically maintained. The volume of extracellular fluid in a young adult male of 70 kg (154 lbs) is 20% of body weight – about fourteen liters.