Introduction to HOMEOSTASIS
Doc Brown's Biology Revision Notes
Suitable for GCSE/IGCSE/O level Biology/Science courses or equivalent
1. What is homeostasis? What is its function?
Negative feedback systems explained
Homeostasis is the maintenance of a stable and constant internal environment in an organism. Homeostasis is crucial to the regulation of an internal environments and enables organisms to adapt to change, both internally and externally. Internal temperature, blood sugar levels, water level and osmotic balance are regulated by a number of organs and systems working together.
The conditions inside your body need to be kept as steady as possible even if the external conditions change. This 'steadiness' or 'regulation' of the 'right conditions' is vitally important for your cells to function properly eg the action of enzymes which control most of your bodies chemistry.
The body controls itself by means of negative feedback systems which constantly help keep conditions right for healthy sustainable life for what you might call 'normal conditions'. Basically if something in the changes beyond a certain limit, then the change is detected and the body automatically responds to balance things up again.
Cells in the body can only survive within narrow physical and chemical limits. They require a constant temperature and pH as well as a constant supply of dissolved food and water. This is why the body requires control systems that constantly monitor and adjust the composition of the blood. These control systems include receptors which sense changes and effectors that bring about changes.
2. How do negative feedback systems work?
There are many automatic control systems in your body that control and regulate your internal environment eg the nervous system, hormone molecule communication. Other control systems 'monitor' things such as your body temperature, water content and blood glucose levels.
The table below illustrates the general principles of maintaining the ideal 'level' of something e.g. temperature, blood glucose, and water via three 'components' working in conjunction with one another to keep conditions steady. These are ...
Note: The coordination centre = control centre, just different phrases meaning the same thing!
This negative feedback detection system process is continuous so that there is always a small fluctuation from the 'NORMAL', illustrated by the graph below (green line ~normal).
The graph shows several decreases and increases as the negative feedback system clicks into action.
Our negative feedback systems work well if external or internal changes are small, i.e. within certain limits, BUT, if the environment (ambient conditions) change too much, then our body might not be able to counteract the enforced change.
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