Skin Senses
Pressure, Temperature & Pain
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
• Only pressure has identifiable neural receptors –
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)
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 "itchsensitive" neurons that respond
to histamines.
Gate-control Theory of Pain
• Pain is registered by free
nerve endings
• 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 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
Activates
(located in skin, muscles, &
internal organs)
Carries Message To…
3. Spinal Cord
1. Intense Stimulus
(which releases substance P)
(too much pressure, heat,
tissue damge)
causes
Pain is reduced
Pain is intensified
Closes the Gates
Leaves Gates
Open
4. Other Neurons to activate
& send pain message to the
Thalamus through open
Spinal Gates. Brain then…
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.
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–
–
–
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 “gateclosing” 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
Virtual Reality Distracts the Brain
• The burn victim’s brain is less responsive
to painful stimulation, as shown by these
MRI scans
An Acupuncturist's Nightmare
Watch Video Clip
Pain and Phantom Pain
• The brain comes prepared to anticipate that it will be
getting information from the limbs of the body. This is
why amputees may experience sensations in a phantom
limb.
• Phantom limb sensations – the brain is misinterpreting
central nervous system activity that occurs in absence of
the normal sensory input from that limb. This can be true
of the other senses as well.
• Play “Phantom Limb Pain: Fooling
the Mind” (4:29) Segment #20 from
The Mind: Psychology Teaching
Modules (2nd edition).