Expert: Dana Krempels, Ph.D. - 8/31/2007

Question
Dear Dr. Krempels,
I know that many harmful stimuli can cause pain to humans (a cut, a headache, etc.)and therefore provoke a conscious self-preservation reaction to the damage. But I came to know that some other damaging stimuli, such as infection, do not necessarily involve suffering or a conscious reaction and that the body can defend itself automatically.

Could you just give me a few examples of automatic defense responses to harmful stimuli or stresses that do not involve both pain and conscious reactions in humans?

I swear this is not a homework...I've done political science but biology is a hobby :).

Thank you for your time and have a good day,

Regards.

Answer
Dear Jack,

The only other automatic defense response I can think of off the top of my head is the reflexive blink we do--even before we are conscious of an object approaching the eye--to avoid a flying foreign object from hitting the eye.  It's a good thing it's a reflex, because if we had to be conscious of the approaching object before we blinked, we'd probably all be walking around with ulcerated corneas!

If you consider other homeostatic mechanisms to count as responses to harmful stimuli, then I guess you could also include all the detoxification done by the liver when we unknowingly ingest toxins (alcohol, nicotine, etc.).  That poor liver is working away to undo our bad behavior, and it gets no respect.  :)

Hope that helps!

Dana