Homeostasis refers to which of the following

One of the most obvious physical responses to overheating is sweating, which cools the body by making more moisture on the skin available for evaporation. On the other hand, the body reduces heat-loss in cold surroundings by sweating less and reducing blood circulation to the skin. Thus, any change that either raises or lowers the normal temperature automatically triggers a counteracting, opposite or negative feedback.

Here, negative merely means opposite, not bad; in fact, it operates for our well being in this example. Positive feedback is a response to change from the normal condition that increases the departure even more.

For example, if a person's temperature is raised to about degrees Fahrenheit, the negative feedback systems stop operating. A person with a high fever has hot, dry skin if they do sweat to help cool it.

Not only have the negative feedback systems shut down in such a case; the increased temperature speeds up the body chemistry, which causes the temperature to rise even more, which in turn speeds up the body chemistry even more, and so forth. This vicious cycle of positive feedback, a "runaway" process, can only end in death if not stopped. It is important to emphasize that homeostatic reactions are inevitable and automatic if the system is functioning properly, and that a steady state or homeostasis may be maintained by many systems operating together.

For example, flushing is another of the body's automatic responses to heating: the skin reddens because its small blood vessels automatically expand to bring more heated blood close to the surface where it can cool.

Shivering is another response to chilling: the involuntary movements burn body tissue to produce more body heat. This alternate model of homeostasis, known as allostasis, implies that the ideal set point for a particular variable can shift in response to transient environmental changes, according to a article in Psychological Review. The point may shift under the influence of circadian rhythms, menstrual cycles or daily fluctuations in body temperature.

Set points may also change in response to physiological phenomena, like fever, or to compensate for multiple homeostatic processes taking place at the same time, according to a review in Advances in Physiology Education.

For example, in anticipation of a meal, the body secretes extra insulin, ghrelin and other hormones, according to a review in Appetite. This preemptive measure readies the body for the incoming flood of calories , rather than wrestling to control blood sugar and energy stores in its wake. The ability to shift set points allows animals to adapt to short-term stressors, but they may fail in the face of long-term challenges, such as climate change. But they're not designed to last for long.

Homeostatic systems may have primarily evolved to help organisms maintain optimal function in different environments and situations. The th eory posits that homeostasis makes it easier for organisms to extract important information from the environment and shuttle signals between body parts.

Regardless of its evolutionary purpose, homeostasis has shaped research in the life sciences for nearly a century. Role of the kidneys in the regulation of intra- and extra-renal blood pressure. Ann Clin Hypertens. Pancreatic regulation of glucose homeostasis.

Exp Mol Med. Recent advances in thermoregulation. Advances in Physiology Education. Molnar C, Gair J. Homeostasis and osmoregulation. In: Concepts of Biology - 1st Canadian Editio n. BCcampus; Your Privacy Rights. To change or withdraw your consent choices for VerywellMind.

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I Accept Show Purposes. Table of Contents View All. Table of Contents. Maintaining Homeostasis. What Is Homeostasis? How Addiction Affects Homeostasis. Was this page helpful? Thanks for your feedback! Sign Up. As glucose concentration in the bloodstream drops, the decrease in concentration—the actual negative feedback—is detected by pancreatic alpha cells, and insulin release stops. This prevents blood sugar levels from continuing to drop below the normal range.

Humans have a similar temperature regulation feedback system that works by promoting either heat loss or heat gain Figure 1. This arrangement traps heat closer to the body core and restricts heat loss.

If heat loss is severe, the brain triggers an increase in random signals to skeletal muscles, causing them to contract and producing shivering. The muscle contractions of shivering release heat while using up ATP.

The brain triggers the thyroid gland in the endocrine system to release thyroid hormone, which increases metabolic activity and heat production in cells throughout the body.

The brain also signals the adrenal glands to release epinephrine adrenaline , a hormone that causes the breakdown of glycogen into glucose, which can be used as an energy source. The breakdown of glycogen into glucose also results in increased metabolism and heat production. Water concentration in the body is critical for proper functioning. Watch this video to learn more about water concentration in the body. Which organ has primary control over the amount of water in the body?

A deviation from the normal range results in more change, and the system moves farther away from the normal range. Positive feedback in the body is normal only when there is a definite end point.

Childbirth at full term is an example of a situation in which the maintenance of the existing body state is not desired. And the events of childbirth, once begun, must progress rapidly to a conclusion or the life of the mother and the baby are at risk. The extreme muscular work of labor and delivery are the result of a positive feedback system Figure 1. The first contractions of labor the stimulus push the baby toward the cervix the lowest part of the uterus.

The cervix contains stretch-sensitive nerve cells that monitor the degree of stretching the sensors. These nerve cells send messages to the brain, which in turn causes the pituitary gland at the base of the brain to release the hormone oxytocin into the bloodstream.