Hormones
Endocrinology is the study of chemical communication systems that provide the means to control a huge number of physiologic processes. Like other communication networks, endocrine systems contain transmitters, signals and receivers that are called, respectively hormone producing cells, hormones and receptors. What exactly are hormones and how are they different from "non-hormones"? Hormones are chemical messengers secreted into blood or extracellular fluid by one cell that affect the functioning of other cells. Most hormones circulate in blood, coming into contact with essentially all cells. However, a given hormone usually affects only a limited number of cells, which are called target cells. A target cell responds to a hormone because it bears receptors for the hormone. In other words, a particular cell is a target cell for a hormone if it contains functional receptors for that hormone, and cells which do not have such a receptor cannot be influenced directly by that hormone. Reception of a radio broadcast provides a good analogy. Everyone within range of a transmitter for National Public Radio is exposed to that signal (even if they don't contribute!). However, in order to be a NPR target and thus influenced directly by t
A stalk links the pituitary to the hypothalamus, which controls release of pituitary hormones. The Thyroid GlandThe thyroid gland is located in the neck. In other words, they act like the "normal" hormone, although perhaps more or less potently. The "stalk" is a long duct which runs down the center of the pancreas and the "grapes" are clusters of cells which flow into this duct and later into the duodenum for digestion of proteins, fats and carbohydrates. The "head" (the right-hand end which is the broadest part of it) lies within the curve of the duodenum. They take instruction from the pituitary glands and have important effects on physical characteristics, development and growth. In some parts of the world, iodine is so scarce that most of the population have goiters. " The female, unlike the male, does not manufacture the sex cells. Most of the pancreas consists of tissues which are embedded in "nested" cells. The PancreasThe pancreas contains exocrine cells that secrete digestive enzymes into the small intestine and clusters of endocrine cells (the pancreatic islets). These glands are about one to two inches in length and weigh only a fraction of an ounce each while secreting more than three dozen hormones. After a meal, blood glucose levels rise, prompting the release of insulin, which causes cells to take up glucose, and liver and skeletal muscle cells to form the carbohydrate glycogen. · Rate of degradation and elimination: Hormones, like all biomolecules, have characteristic rates of decay, and are metabolized and excreted from the body through several routes. In addition to producing eggs or "ova," the ovaries produce female sex hormones called estrogen and progesterone.
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Acceptance Essays
