Homeostasis
What?
Homeostasis is all about balance. Looking at my unit outline, there is not much time spent specifically on this subject - but it reaches out is to many other fields, and the effects can be enormous.
Keeping balance is easy, you do it all the time. Stand up, and you will not fall down. You can balance on your two feet. No balance, you fall down, you hurt yourself. Same with pretty much every system in your body.
Take, for example, your body temperature. This should be 36.8 °C. If it drops below that point, your body will start shivering in order to produce heat, additionally goosebumps will appear on your skin to retain heat. If you get too hot, your blood vessels near your skin dilate to let of more heat.
“Keeping the internal body constant is called Homeostasis. It is a state of Dynamic Equilibrium.“
(Dynamic equilibrium: always being adjusted and tweaked to be in balance)
Other systems that are regulated by homeostasis include levels of salt, carbondioxide water and oxygen in your body.
A basic look at how this is achieved shows that there are three components required for a control system
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Receptors: Gather the required information, e.g. what is the current body temperature?
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Integrators: These decide what needs to be done, whether everything is fine or a correction is needed.
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Effectors: Enforcement of any necessary corrections
How?
There are two ways that homeostasis is regulated: Threough the nervous system (short term)and through the endocrine system (long term). Imagine yourself in minor car accident. The initial shock come from your nervous system, it acts quickly and does not last long. But does the feeling wear off half an hour later? Nope. Your endocrine system has kicked in and taken over that part for the nervous system.
Clever aye?
More How.
The body has two mechanisms:
Negative feedback - decreases the likelihood that the action would happen again
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Real World example: Telling a child off for bad behaviour: you don’t want that happening again.
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The mechanisms that is used in most regulatory systems in the body
An example would be the regulation of blood sugar levels in the bloodstream. The brain insists on blood sugar levels being at exactly 90mg of glucose per 100ml of blood. (to quote Dr Richard Brightwell: “The brain is lazy, selfish and tells you lies”).
In case your glucose levels rise above that, your pancreas releases insulin (making cells more permeable to glucose to help absorbtion) until an appropriate level is reached.
Same story if your glucose levels drop below the 90mg/100ml, your pancreas releases glucagon in to the blood stream
Positive feedback - increases the probability that the action will happen again
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Real world example: Praising a child for good behaviour: You want to encourage this to happen again.
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Not found very often in the body.
Childbirth is a great example: The soon-to-be born baby, just by being in the uterus, exerts pressure against the wall of the uterus, which acts as a trigger to release Oxytocin (which is a hormone that makes smooth/involuntary muscles contract. Females have more smooth muscles than males: in their uterus). Relesing oxytocin contracts the uterus, the baby exerts more pressure upon the uterus, more oxytocins is released - a cycle. These contractions are called – you guessed it – contractions, and stop after the stimulant (baby) has been removed (born). No need for the uterus to contract anymore!
Actually, that is not true. Apparently the mammary glands are another area of the body where one can stimulate the release of oxytocin. After childbirth, the uterus is not quite the size it used to be, still pretty stretched. More oxytocins equals more contraction equals a uterus that more represents it’s original state. An interesting fact that goes with this is the rising number of hysterectomies that occurred during the 1970’s, following the introduction of artificial mothers milk, so mums in the 1950’s did not have to breast feed (and apparently weren’t encouraged to do so). They did not receive enough oxytocins. Their uterus were left in a semi-stretched state, thinner and bigger that natural, an ideal breeding ground for bacteria.
Morale: Everything happens for a reason.
