Module 1.6d�Skin Senses�Pressure, Temperature & Pain

Learning Targets

• LT 1.6-12

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• LT 1.6-13

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Explain the four basic touch sensations, and explain how we sense touch.

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Compare and contrast the biological, psychological, and social-cultural influences that affect our experience of pain, and explain how placebos and distraction help control pain.

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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 other sensations evoked by different combinations and intensity (e.g., tickling, hot, itching, etc.)

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 both warm 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)

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Cold + Warm Receptors = HOT!!!

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.

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Biopsychosocial Perspective

• Our experience of pain is much more than neural messages sent to the brain.

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Gate-control Theory of Pain

• Pain is registered by Nociceptors:
• a type of free nerve ending that 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.

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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

1. Intense Stimulus�(too much pressure, heat, tissue damge)

Activates

2. Free Nerve Endings

(located in skin, muscles, & internal organs)

Carries Message To…

3. Spinal Cord

(which releases substance P)

causes

4. Other Neurons to activate & send pain message to the Thalamus through open Spinal Gates. Brain then…

Leaves Gates Open

Closes the Gates

Pain is reduced

Pain is intensified

Psychological & Cultural Influences on Pain

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

Controlling Pain

• Pain control therapies may include
• Drugs
• Surgery
• Acupuncture
• Electrical Stimulation
• Massage
• Exercise
• Hypnosis
• Relaxation Training
• Meditation
• Thought Distraction
• Placebos have also been found to be helpful in controlling pain (simply because people believe in their power)

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

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• The burn victim’s brain is less responsive to painful stimulation, as shown by these MRI scans

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An Acupuncturist's Nightmare

Watch Video Clip