Positive and Negative Feedback Mechanisms

[Jezza]

Can someone please give me a simple definition for both the feedbacks and an example if they can.

I just don't seem to understand it despite reading about it numerous times.

[Starlight]

Think of specific examples:

negative feedback- you want to counteract something

So there is some 'condition' in the body that has causes the 'set point' to change. For example, this might be that you are cold.

So the hypothalamus (control centre) detects this and 'tells' the effectors, that the body is not at it's normal 37 degrees, but in fact below. The effectors here, decrease heat loss and try to generate heat (for example the formation of goosebumps- create an insulation of hair).

Then you'll get the response, hopefully that the person is warmer.

Positive feedback is the opposite, the feedback signal increases, leading to more modification.

So for example, birth

http://www.google.com.au/imgres?q=birth+positive+feedback&um=1&hl=en&biw=1366&bih=576&tbm=isch&tbnid=0P_xzX33CIFVRM:&imgrefurl=http://biologyfiles.fieldofscience.com/2011_01_01_archive.html&docid=h4qD63lHLLtQnM&imgurl=http://www.mattk.com/images_mk/homeostasis-pregnancy-positive-feedback.jpg&w=800&h=402&ei=3fKXT4CCIoWZiAf78qzjBQ&zoom=1&iact=hc&vpx=208&vpy=157&dur=775&hovh=159&hovw=317&tx=209&ty=92&sig=113943409112138570985&page=1&tbnh=75&tbnw=149&start=0&ndsp=24&ved=1t:429,r:1,s:0,i:67

So here, the stimulus (i.e. the baby is coming has been detected) and rather than aim to reverse this change, the body wants to amplify this process (to get the baby out and the mum out of excruciating pain )

haha hope this sort of helped