Touch • Touch receptors are on the skin • Skin is the largest & heaviest organ • (20 sq. ft. & 6 lbs.) • Four basic skin senses are • Pain, warmth, cold, and pressure • All skin sensations are a combination of these four basic senses
Pressure • Pacinian Corpusle – located beneath the skin, it converts pressure stimulation into neural messages it sends to the brain. • Constant pressure causes sensory adaptation and it either reduces the number of signals or quits sending them all together. (like the clothes on your body) • Sensory receptors are located unevenly on the body so certain areas are more sensitive than others.
Temperature • Temperature is sensed by specific spots that produce either cold or warm sensations. • Cold spots can be triggered by cold or a hot stimulus. • Warm spots only respond to warm stimulus of about 105 degree Fahrenheit. • If bothwarm and cold spots are stimulated at the same time you will feel HOT. • Various combinations of skin sensations produce different results • Check out the Amazing Hypothermia Man (2 min) • Is it mind over matter/cold? Check out this YouTube Clip (2 min)
What purpose does pain serve? • Pain is your body’s way of telling you something is wrong. It tells you to change your behavior immediately. • Any external stimulus that can produce tissue damage can cause pain. • Internal stimuli like disease or infection can also cause pain. • Certain areas of the body are more sensitive than others • Itch is caused by "itch-sensitive" neurons that respond to histamines.
Gate-control Theory of Pain • Pain is registered by Nociceptors: • a type of free nerve endingthat detects hurtful temp, pressure or chemical • Pain messages travel on one set of nerve fibers containing pain gates. • The gates are open when pain is felt. • Other sensory messages go through another set of fibers. • The nonpain fibers, endorphins & distraction can close the pain gates to stop the sense of pain.
The Process of Gate-Control Theory • Intense stimulus activates small-diameter sensory fibers called free nerve endings. • Free nerve endings carry their messages to the spinal cord, releasing a neurotransmitter called substance P that activates other neurons to send their messages through the open spinal gates to the thalamus. • Thalamus sends pain signals to parietal, frontal lobes and limbic system. • Brain interprets pain and sends messages to the spinal cord to either close or open gates. If more gates open, pain gets worse. If gates close, less pain experienced. • Endorphins can be released which inhibit the release of substance P thus lessening pain. Acupuncture may work in this way. • Muscle Tension, psychological arousal and rapid heart beat can all produce or intensify pain.
The Pain Process 2. Free Nerve Endings (located in skin, muscles, & internal organs) Carries Message To… Activates 3. Spinal Cord (which releases substance P) • Intense Stimulus(too much pressure, heat, tissue damge) causes Closes the Gates Pain is reduced 4. Other Neurons to activate & send pain message to the Thalamus through open Spinal Gates. Brain then… Leaves Gates Open Pain is intensified
Biopsychosocial Perspective • Our experience of pain is much more than neural messages sent to the brain.
Can we distract ourselves from the pain? YES! • An athlete who is injured doesn’t realize it until after the game. • Emotions and cultural differences can influence the brain's decisions on opening or closing gates. • Person's mental state can influence one's experience of pain. • Distraction – focus on a nonpainful stimulus • Imagery – create a vivid mental image can help control pain. • Positive Self Talk – "It hurts, but I'm OK." Or redefine pain. • Counter irritation – create a strong competing sensations that's mildly stimulating or irritating. Rubbing a sore area. Stimulating the “gate-closing” nerve fibers can help lessen pain. Rubbing a stubbed toe creates a competing stimulation that will block some of the pain messages. Putting ice on a bruise sends cold messages to the brain which lessen the pain messages. • Relaxation – Deep breaths and relaxing deeply
Virtual Reality Pain Control • For burn victims undergoing painful skin repair, an illusory virtual reality can powerfully distract attention, thus reducing pain and the brain's response to painful stimulation • The burn victim’s brain is less responsive to painful stimulation, as shown by these MRI scans
An Acupuncturist's Nightmare Watch Video Clip