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. Oxytocin causes stronger contractions of the smooth muscles in of the uterus the effectors , pushing the baby further down the birth canal.
This causes even greater stretching of the cervix. The cycle of stretching, oxytocin release, and increasingly more forceful contractions stops only when the baby is born.
At this point, the stretching of the cervix halts, stopping the release of oxytocin. A second example of positive feedback centers on reversing extreme damage to the body. Following a penetrating wound, the most immediate threat is excessive blood loss. This command can cause several responses. If you are too hot, the skin makes sweat and blood vessels near the skin surface dilate. This response helps decrease body temperature. Another example of negative feedback has to do with blood glucose levels.
When glucose sugar levels in the blood are too high, the pancreas secretes insulin to stimulate the absorption of glucose and the conversion of glucose into glycogen, which is stored in the liver.
As blood glucose levels decrease, less insulin is produced. When glucose levels are too low, another hormone called glucagon is produced, which causes the liver to convert glycogen back to glucose. Feedback Regulation. If a raise in body temperature stimulus is detected receptor , a signal will cause the brain to maintain homeostasis response. Once the body temperature returns to normal, negative feedback will cause the response to end. This sequence of stimulus-receptor-signal-response is used throughout the body to maintain homeostasis.
Some processes in the body are regulated by positive feedback. Positive feedback is when a response to an event increases the likelihood of the event to continue. An example of positive feedback is milk production in nursing mothers. As the baby drinks her mother's milk, the hormone prolactin, a chemical signal, is released. Muscles contract and relax rapidly, which generates heat to keep you warm. The hair on your skin rises, trapping more air, which is a good insulator, near your skin.
So what happens when you have a fever? Does this mean your body is unable to maintain its homeostasis, in the same way your house will get too hot if your air conditioner is broken? In extreme cases, a fever can be a medical emergency; but fever is an adaptive physiological response of our body to certain infectious agents. Certain chemicals called pyrogens will trigger your hypothalamus to shift the set point to a higher value.
This is more like you programming the thermostat in your house to a higher temperature to save energy on a hot day when you are not going to be home during the day. These pyrogens can come from microorganisms that infect you, or they can be produced by your body cells in response to an infection of some sort.
The increased temperature may actually impair the replication of infecting bacteria and viruses that are adapted to survive best at your normal homeostatic body temperature range.
This can give your immune cells a chance to destroy the microorganisms before they can rapidly multiply and spread in the body. There is also some indirect evidence that increased body temperature slightly modifies several metabolic reactions in ways that also allow the immune system to function more efficiently.
As long as the pyrogen levels continue to increase and decrease you will feel like you are swinging back and forth. Body functions such as regulation of the heartbeat, contraction of muscles, activation of enzymes, and cellular communication require tightly regulated calcium levels. Normally, we get a lot of calcium from our diet. The small intestine absorbs calcium from digested food. The endocrine system is the control center for regulating blood calcium homeostasis.
The parathyroid and thyroid glands contain receptors that respond to levels of calcium in the blood. In this feedback system, blood calcium level is the variable, because it changes in response to the environment. Changes in blood calcium level have the following effects:.
Calcium imbalance in the blood can lead to disease or even death. A number of organs are involved in homeostasis, and these include the lungs, pancreas, kidneys and skin. Homeostasis is the process that the body uses to maintain stability. The lungs are involved in respiration, exchanging carbon dioxide in the bloodstream for oxygen from the air.
The pancreas regulates blood-glucose levels with the release of insulin or glucagon. The hypothalamus detects how much water is present in the blood, and controls how much water the kidneys hold or excrete in urine. The skin controls body temperature in two ways. It releases sweat to cool the body when its temperature is too high, and it flattens or stands up body hairs to release heat or insulate the body, depending on what the body needs.
Respiration is a process that uses glucose to create energy. It is the most important reaction taking place within the human body. Critical to the respiration process is the regulation of oxygen levels within the blood, which is carried out by the lungs. In addition to energy, respiration creates carbon dioxide from the broken down glucose.
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