P5
Homeostasis is where the body keeps a constant internal environment. This involves all the metabolic processes taking place In the body as well as the blood, tissue fluid and all the contents in the body 's cells. There are a range of variables from heart rate to the blood glucose levels that the body will take into account.
Negative feedback will occur when something changes from its normal in the body. The body then will come back with a response to cancel out the difference to bring it back to its normal. An example of this is if blood glucose level falls the body will then convert the glycogen in the body to glucose which will bring back the energy in the cells to its normal amount. This system requires receptors so that they are able to detect the change in your body. As well as receptors it also needs a control centre so that the information that has just been received can be processed to then give the correct response of what the body should do. Most of the control centres can be found in the brain. It will also need effectors so that after the change has happened and the body is back to normal it can reverse the change to keep the body at its original state.
The brain and the central nervous system controls something called the homeostatic mechanisms. This is when they anticipate whether there may be a rise or a fall compared to that of the normal. An example of this is the feeling of being cold or tired this is a result of having not eaten for a sufficient period of time. This has then been sent as a message to the brain which your brain will then tell you to eat so that the energy you get from the nutrients in your food will counteract those feelings and make them disappear. As this is an anticipation from the central nervous system and the brain it is called feed forward as it hasn 't happened yet.
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Bibliography: Edexcel Level 3 Health and Social Care Book http://www.ehow.com/how-does_5101742_describe-regulation-blood-glucose-levels.html