2. The perception of pain; any painful sensation.
Pain exists beyond a simple touch
Beyond the pleasures and assurances of touch, there is always the looming possibility of pain. As a survival mechanism, pain warns our brains of danger and tells us to act to correct the situation, or to avoid whatever caused the pain.
Is there anyone who does not have vivid memories of burning one's hand on a hot stove and quickly withdrawing it? Pain is a powerful reminder and so we learn to be very careful and to avoid whatever caused it.
Pain does not always warn us of danger. It comes too late for us to avoid a bad sunburn, and a tumor in the brain can grow unnoticed because the tissue within our skulls has no pain receptors.
Pain receptors, or free nerve endings, are spread over a larger area than any of the other sensor receptors. They completely ignore light contact, and only fire up if the stimuli threaten to damage the tissue.
There are more pain receptors in the skin than other types of skin sensors, but they are not evenly distributed; for example, the neck and eyelids are densely covered, but there are few receptors on the soles of the feet and on the balls of the thumb, which is why a needle prick for a blood sample is often done on one of the thumbs.
Unlike touch receptors, pain receptors usually do not adapt; or barely adapt in some cases, so the nerve continues to transmit as long as there is pain.
After damage to the tissue has been done; however, the warning function is over and the pain falls off.