Touch – The Skin Senses
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Role in development
Role in human interaction (see elephants on acid – “touching strangers”)
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Pressure
Warmth
Cold
Pain
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Most sensitive to stimulation not expected
Touch sensitivity varies depending on where it is on the body.
o Two-point threshold.
Pain
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Purpose – tells your body when something has gone wrong
Quick attention to change your behavior
Imagine life without pain – typically don’t make it to adulthood
Imagine life with chronic pain – backaches, headaches, arthritis, cancer-related
What is Pain?
 Pain is in the brain
o Phantom limbs
o True of all senses – it is just as much brain as senses (tinnitus, phantom
smells, nerve-damaged taste buds can create phantom tastes…)
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Gate-Control Theory
o Spinal cord contains a neurological “gate” that blocks pain signals or
allows them to pass to the brain.
o Basis = the same fibers that send signals of warmth, cold, rough, smooth
conduct pain, so you can send mixed messages to close the “gate.”
 Rub area around your stubbed toe.
 Ice on a bruise (also relieves swelling)
 Some with arthritis where electronic stimulation unit to feel
vibration instead of pain.
o Also – the brain has influence over this “gate.”
 Sports players not noticing injury during intense game.
Memory of pain
o Not dependant on the “net pain” (full duration), but we remember the
worst part.
 Painfully cold water for 60 sec = 30 reg. Cold preferred over 60
painfully cold.
 Physicians know – let the pain last longer and don’t make any
memories.
Pain Control
 If pain is physical + psychological, we should be able to treat it at both ends.
 Lamaze
 Nurse talking to you while giving you a shot.
Taste (Gustation)
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Chemical sense (Chemoreception – gustation and olfaction)
Sweet, sour, salty, bitter (savory - umami)
o All other tastes are mixtures of these
Tough to find specific nerve fibers for each, but we do recognize some regions
o Show tongue overhead
Each bump on top and sides has 200 taste buds (approx. 10,000 total)
o Each taste bud contains a pore that collects taste chemicals
o Each pore has approx. 50 taste receptor cells that are like antennae
o Taste buds reproduce receptor cells (burning your tongue)
Taste buds # and sensitivity decrease over time
Supertasters (25%), tasters (50%), nontasters (25%) – determined by # papilla
(fungiform, filliform)
 Ability to recognize taste with the tongue is to avoid poison.
Smell and Taste
 Starburst experiment
 Eating when you have a cold
o Demonstrated the importance of smell in “taste.”
 Anosmia (inability to smell) – inability to taste well
Sensory Interaction
 Principle that one sense may influence another, mostly smell and taste.
o Another example is seeing a person helps us correctly perceive a voice as
directly in front of us.
Smell (Olfaction)
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Chemical sense
Only sense not processed through the thalamus
5 million receptor cells at the top of each nasal cavity
o Olfactory receptor cells are like anemones in the reef.
Detect approx. 10,000 odors through these receptors that work together. (Not one
molecule for each odor.)
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Very primitive structure and process
o Original purpose – sniff for food and predators
o Animals use this for biological purposes – salmon to breeding ground,
moths to mates, sharks to food, etc
o Humans have other senses that are now far more accurate/helpful
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Strong at triggering memories
o State-dependency (learn while smelling chocolate, better memory w choc)
o Mood congruency (smelling something pleasant evokes good memories)
Body Position and Movement
Kinethesis – system for sensing the position and movement of individual body parts.
 Wake up in the middle of the night, how your body is positioned
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Every little twist or turn is sent to brain.
Book discusses a man who loses this sense – he cannot walk or eat without the
assistance of his sense of sight.
Vestibular Sense – sense of body movement and position; including balance
 Semicircular canals (above cochlea)
 Vestibular sacs (connect canals with cochlea)
o These contain fluid that moves when the head rotates or tilts
o Send information to brain, allowing you to sense your (full) body position
 Spinning around – doesn’t go back to normal too fast, resulting in
the perception that you are still spinning.
Sensory Restriction (Deprivation)
 Bad: solitary confinement, participants in a 1957 study on sensory deprivation
(hallucinations, depression, disoriented, and suggestible).
o But what is causing this – could be stress of confinement
 Good: meditative state, no stimulation can help focus the mind