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An endocrine hormone is released by a specific gland and travels throughout the body in the bloodstream to reach its target cell, where it will exert a certain effect. Each hormone recognizes their target cells from the many other cells in the body by means of the receptors that exist on the cell, which they are able to bind to.
The receptor then initiates a series of chemical reactions within the cell to produce the intended effect of the hormone. For example, many endocrine hormones may stimulate the release of a chemical that induces or prevents the production of a certain gene.
After the action of the hormone, the release of the
hormone from the endocrine gland must be regulated by a negative feedback loop to control the process and prevent the continuous and excessive activation of receptors.
Hormonal Regulation
Various processes in the endocrine system help to regulate the secretion of hormones and the resulting actions. This is essential for the body to maintain control over the action of the hormones. In other words, regulation is required to allow a hormone to initiate the intended reaction when needed and bring it to an end once the action has been completed.
For example, when the body is stressed the hypothalamus gland begins to
secrete the
corticotropin-
releasing hormone (CRH) into the blood. This travels to the anterior pituitary gland to stimulate the release of adrenocorticotrophic hormone (ACTH). ACTH then travels in the blood to the adrenal glands, to stimulate the adrenal cortex cells which secrete the hormone cortisol.
Cortisol is responsible for stimulating the liver and skeletal muscles to increase the metabolism of glycogen (a storage form of glucose) so as to increase the blood glucose levels. The aim is to provide more energy as a response to the initial stimulus of stress.