http://www.ck12.org Chapter 1. Human Biology
1.48 Touch
- Outline how we sense pressure, temperature, and pain.
What if you felt no pain?
It might sound good to you to have a condition where you feel no pain. But actually this type of condition would be
very dangerous. What would happen if you strained your back but felt no pain? Instead of resting your back, you
might injure it further.
Touch
When you look at the prickly cactus pictured below (Figure1.95), does the word "ouch" come to mind? Touching
the cactus would be painful. Touchis the sense of pain, pressure, or temperature. Touch depends on sensory
neurons, or nerve cells, in the skin. The skin on the palms of the hands, soles of the feet, and face has the most
sensory neurons and is especially sensitive to touch. The tongue and lips are very sensitive to touch as well. Neurons
that sense pain are also found inside the body in muscles, joints, and organs. If you have a stomach ache or pain
from a sprained ankle, it’s because of these sensory neurons found inside of your body.
The following example shows how messages about touch travel from sensory neurons to the brain, as well as how
the brain responds to the messages. Suppose you wanted to test the temperature of the water in a lake before jumping
in. You might stick one bare foot in the water. Neurons in the skin on your foot would sense the temperature of the
water and send a message about it to your central nervous system. The frontal lobe of the cerebrum would process
the information. It might decide that the water is really cold and send a message to your muscles to pull your foot
out of the water.