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The concept of the regulation of the internal environment was described by French physiologist Claude Bernard in 1849, and the word homeostasis was coined by Walter Bradford Cannon in 1926. [10] [11] In 1932, Joseph Barcroft a British physiologist, was the first to say that higher brain function required the most stable internal environment.
The regulation of glucose levels through Homeostasis This tight regulation is referred to as glucose homeostasis . Insulin , which lowers blood sugar, and glucagon , which raises it, are the most well known of the hormones involved, but more recent discoveries of other glucoregulatory hormones have expanded the understanding of this process.
Biological processes are regulated by many means; examples include the control of gene expression, protein modification or interaction with a protein or substrate molecule. Homeostasis: regulation of the internal environment to maintain a constant state; for example, sweating to reduce temperature
An example of downregulation is the cellular decrease in the expression of a specific receptor in response to its increased activation by a molecule, such as a hormone or neurotransmitter, which reduces the cell's sensitivity to the molecule. This is an example of a locally acting (negative feedback) mechanism.
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.
This places homeostasis as a function within allostasis; however, some argue it is a larger paradigm altogether. [14] Allostasis redefines health and disease beyond the stable measures from lab tests or blood pressure, for example; and expands it to define health as the flexibility of these values.
An example is a system in which a protein P that is a product of gene G "positively regulates its own production by binding to a regulatory element of the gene coding for it," [14] and the protein gets used or lost at a rate that increases as its concentration increases. This feedback loop creates two possible states "on" and "off".
Energy intake is measured by the amount of calories consumed from food and fluids. [1] Energy intake is modulated by hunger, which is primarily regulated by the hypothalamus, [1] and choice, which is determined by the sets of brain structures that are responsible for stimulus control (i.e., operant conditioning and classical conditioning) and cognitive control of eating behavior.