![]() After you have eaten a meal, the blood glucose levels will begin to rise because the carbohydrates in the fo The hormones responsible for regulating blood glucose are produced in the pancreas in particular areas called islets of Langerhans. The amount of glucose in your blood is carefully controlled. Changes in temperature bring about nerve impulses from the brain to the muscles and glands which will bring about changes depending on whether it is hot or cold. ![]() The temperature in mammals is detected by thermoreceptors in the skin and the hypothalamus which is in the brain. There are two types of heat regulation: endothermic where the species controls their own temperature (mammals, birds), and ectothermic where temperature reflects the environmental temperature (lizards, fish). It is important to maintain a constant temperature so that living organisms can maintain metabolism. ![]() Note that the opposite change takes the level too far below the normal, therefore a negative response backup will occur, and the process repeats itself, so that over time the temperature oscillates about the normal, within small limits. The diagram below helps to explain this using the example of body temperature. The body will do this by opposing a change that deviates from the normal. Negative feedback is the mechanism by which the body maintains conditions within particular limits. A specific hormone will fit a specific receptor protein, and this brings about a change in that cell. Hormones are made of proteins, they are released by glands into the bloodstream, where they reach target cells. Hormones have an important role in this system. Homeostasis: Negative Feedback, Body Temperature, Blood Glucoseħ Parts: Homeostasis is the maintenance of a constant internal environment in response to a changing external environment. When the furnace produces enough heat to elevate temperature above the set point of the thermostat, the thermostat is triggered and shuts off the furnace (heat is feeding back negatively on the source of heat) The heating system in your home is a simple negative feedback circuit. Negative feedback is seen when the output of a pathway inhibits inputs to the pathway. Instances of positive feedback certainly occur, but negative feedback is much more common. Feedback Control of Hormone Production Feedback circuits are at the root of most control mechanisms in physiology, and are particularly prominent in the endocrine system. Shutting off secretion of a hormone that has a very short halflife causes circulating hormone concentration to plummet, but if a hormone's biological halflife is long, effective concentrations persist for some time after secretion ceases. 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. Rate of delivery: An example of this effect is blood flow to a target organ or group of target cells - high blood flow delivers more hormone than low blood flow. Such control is mediated by positive and negative feedback circuits, as described below in more detail. The concentration of hormone as seen by target cells is determined by three factors: Rate of production: Synthesis and secretion of hormones are the most highly regulated aspect of endocrine control. Almost inevitably, disease results when hormone concentrations are either too high or too low, and precise control over circulating concentrations of hormones is therefore crucial. The physiologic effects of hormones depend largely on their concentration in blood and extracellular fluid.
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