How Do We Feel Pressure, Temperature and Pain?
The cutaneous or skin senses are composed of the sense of touch, the sense of temperature and the sense of pain. Pressure, temperature and pain are different features of tactile sensation, requiring different kinds of receptors.
Touch, or Pressure, is a form of mechanical energy. Around 500,000 sensory receptors that detect pressure are located in the skin. Sensory information detected by these mechano-receptors travel from the skin to the spinal cord, the brain stem, the thalamus, and finally, to the somatosensory areas in the frontal and parietal lobes. Research findings support that women are significantly more sensitive to touch than men. In an experiment by Susan Lederman and Roberta Klatsky (1998, 2003), they found that index fingers covered with fiber glass sheath are 73% weaker in detecting thin nylon hair, and 32% weaker in distinguishing one object from another by means of texture.
Temperature is detected by thermoreceptors located just below the skin. There are around 16,000 warm thermoreceptors scattered around the body, and about 150,000 cold thermoreceptors. Thermoreceptors not only warn us to avoid skin damage, they also provide the body information to keep its temperature at 98.6 F. A sense of "hotness" is felt when both the warm and cold thermoreceptors are simultaneously and proximally stimulated, and it takes a maximum of 2 seconds to endure the pain.
Sensing Pain is important because it warns the body of possible damage. Presumably because pain can virtually come from all forms of energy - mechanical, thermal and chemical - and because of its important role for keeping the body safe, there are around 4 million pain receptors distributed throughout the body. Pain receptors are anatomically similar to touch receptors, but they require higher thresholds and they respond to a different type of stimuli. Pain receptors are chemoreceptors; they respond particularly to prostaglandins that are released by disrupted tissues.
Painful signals reach the brain in two ways. The Fast Pathway directly connects with the thalamus, providing immediate information about the pain. The Slow Pathway, on the other hand, goes to the limbic system first before it reaches the thalamus, reminding us of the painful feeling. To illustrate how the fast and slow pathways work, imagine that you accidentally dipped your finger in boiling water. The quick reflex to immediately withdraw your finger went through the fast pathway, while the nagging painful feeling of the swollen finger went through the slow pathway.
Sensing pain varies across individuals. Physiological differences, like sensitivity and low endocrine production, and socio-cultural differences involving motivation, attention and expectations, result to varying degree of pain perception. For example, some Indians participate in a hook-swinging ceremony, where a person dangles by a hook pierced onto his back, after blessing all the children and farm fields in a certain area. These Indians report feeling no pain while doing the ceremony. Plus, childbirth is not even considered painful in some cultures.
Pain can also be controlled or reduced. Medically, aspirins can reduce pain by blocking the release of prostaglandins in the body. Because attention can magnify the perception of pain, distraction can be a good way to reduce the feeling of pain. For example, you may opt to look away while being injected with drug. Focused breathing or panting can also help reduce pain. This is because it helps the body relax, stay focused, and keep attention away from pain. The Lamaze Method uses this approach to help pregnant women control and reduce pain during labor. Lastly, counterstimulation may be used to stop sudden or continuous pain. You may pinch your skin after a bad cut, or apply ice to a sprained or swollen area.
Acupuncture is the process of inserting thin needles to various points in the body to produce different effects, mostly therapeutic effects. Although acupuncture is far from being established as a valid medical procedure for promoting health, the practice raised significant speculations on the nature of pain. According to the Gate-Control Theory by Ronald Melzack and Patricia Wall (1965), the spinal column acts as a pain gateway, and the needles in acupuncture close the gate-holes in the spinal column, allowing the person to feel no pain. Some neuroscientists, however, believe otherwise. They claim that very few pain signals originate from the spinal column, and that endorphins are more likely to be responsible for it. These neuroscientists propose that acupuncture releases endorphins in the slow pathway, eliminating painful feeling.