Homeostasis what it is and why the body does it.

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Homeostasis what it is and why the body does it

It is the process in which human body maintains a steady interior environment regardless of the exterior changes. The body organs can only maintain their functions powerfully within only a narrow range of conditions. For example body temperature, acidity, blood pressure, blood glucose levels, heart rate, respiratory rate and water balance.

When a condition changes from where its original point is for working optimally. Its automatic regulatory mechanisms are set to work to work against the annoyance and to re-establish its original point.

In order for homeostasis to occur regardless of which body system is involved receptors are needed to detect changes that are in the exterior environment. A control centre (mostly in the brain) to receive and to act on the information the receptors is giving. Effectors act to bring the system back to normal. This is called negative feedback.

Negative feedback is the most common type of homeostatic control.

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Positive feedback effects are rare because they stimulate greater deviations from the normal and then result in a bust situation. An example of positive feedback is childbirth or the explosion of the foetus because of the continuing stimulation of the uterine muscle. If a person breaths air with a high content of carbon dioxide this is sensed by receptors that cause the breathing rate to increase. Then the person breathes in faster taking in more carbon dioxide that stimulates the receptors more so they breathe even faster. Positive feedback cannot play a role in keeping things constant.

The homeostatic mechanisms involved in controlling breathing rate

The medulla of the brain contains clusters of neurones that represent the respiratory centre. One cluster is responsible for inspiration and the other for expiration. In normal quiet breathing the inspiratory system is active for approximately two second followed by the expiratory centre that is active for three seconds.

Above the medulla in a part of the brain called pons there are two more centres associated with respiration. They are: -

Pneumotaxic centre- inhibits the inspiratory centre as the lungs fill with air allowing expiration to occur.

Apneustic centre- sends ...

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The homeostatic mechanisms involved in controlling breathing rate

Above the medulla in a part of the brain called pons there are two more centres associated with respiration. They are: -

Pneumotaxic centre- inhibits the inspiratory centre as the lungs fill with air allowing expiration to occur.

Apneustic centre- sends impulses to the inspiratory centre to prolong inspiration to occur.

Muscular activity requires a lot of energy therefore cells must respire more rapidly for extra energy to be produced. More oxygen will be consumed as a result of more carbon dioxide and water waste manufacture.

Homeostatic mechanisms involved in controlling heart rate

When any form of excitement, fear, stress or exercise is taken out your brain acts as the control centre. It stimulates the release of adrenalin from the adrenal glands situated at the top of each kidney. It also sends impulses down the synaptic branch of the nervous system to the heart and other organs. These actions boot the heart making it beat harder and stronger. When the heart beats faster it sends more blood around the body. But the blood is distributed between organs and the muscles get the greater share. The skin and the digestive system receive small amounts of blood. This is the reason you will look pale and feel nauseous. This is called a primitive response that enables you to run away or stand and fight. Your blood pressure and breathing rate rise, secretions decrease making your mouth dry and it can be difficult to swallow. Adrenaline is destroyed once the emergency is over. Sympathetic nerve impulses did down and the parasympathetic impulses kick in and slow down the heart rate back to normal.

The sympathetic and parasympathetic branches collect from part of the automatic nervous system and act like a brake and accelerator to the internal organs. The sympathetic is not always an accelerator and the parasympathetic the break sometimes the work the opposite way round on organs.

When there are no emergencies the same two nerves tailor the heart to suit the circumstances. They are influenced by: -

Increase in blood pressure: receptors are sensitive to stretch in the walls of the major blood vessels like the aorta carotid artery are triggered when blood pressure increases they send impulses to the medulla. There is a cardio regulatory centre in the medulla.

Increase in venous return Baroreceptors (stretch receptors) monitor pressure, located in the walls of the aorta and carotid artery monitor the pressure of the blood by responding to stretching of the vessel wall. The stretch receptors are stimulated when more blood is flowing to the right atrium and therefore increase blood pressure. The degree of stretch is feed back to medullar control centres, which output through the nerve and sympathetic pathways modulating the power of the heart.

Low oxygen and increased carbon dioxide concentrations- chemoreceptors can be triggered by high and low concentrations of chemicals, like oxygen carbon dioxide hydrogen ions and ph levels.

Homeostatic mechanism involved in controlling temperature

In your brain is there is an area called the hypothalamus. The hypothalamus has a thermo-regulatory centre and this detects the temperature of your blood. You also have thermo-receptors in your skin and these detect the temperature outside. You can increase your temperature by doing exercise, or putting on extra layers of clothing. You can decrease your temperature by removing clothes, lying in a cool place, etc. At extreme internal body temperatures your body has to employ other strategies. Muscles are also sent messages when you are cold. They make you shiver, warming you up. Your Low Critical Temperature is about 27° C and at temperatures this low your metabolic rate changes. At your Lower Lethal Temperature (about 25° C) your system will collapse and you will probably die. Your High Critical Temperature is very high, but if it is reached your metabolic rate cannot decrease to lower it. It increases out of control. If your Upper Lethal Temperature of about 42°C is reached you will die.