PY460: Physiological Psychology

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Transcript PY460: Physiological Psychology

Chapter Seven- modules 2 & 3
7.2: The Mechanical Senses
7.3: The Chemical Senses
Slide 2: The Mechanical Senses
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The Mechanical Senses
 senses responsive to change in pressure, bending, or other structural
change in a receptor
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Past Chapter on movementstretch receptors & stretch reflexes
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This Chapter
somatosensation: touch, pain, temperature
vestibular sensation: position and movement of head (leads to
corresponding adjustments in posture, eye movements)
Slide 3: Vestibular Sensation
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TRY IT: “Jiggle head and read, Then Jiggle Book”
Why is it easier to read when you jiggle head?
Vestibular Organs- adjusts for direction, tilt of head
3 semicircular canals- 3 planes, sends APs to cerebellum &
brain stem via crainial nerve
2 otolith organs- sensitive hairs on H & V axis
Slide 4: Somatosensation: Sensation of the body
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Somatosensation- sensation of body and its movements
 light touch, deep pressure, shape, temperature, pain & position of joints
Location of many SS
receptors- Skin-the body’s
largest organ.
Free nerve endings- Pain
Pacinian Corpuscle- Sudden
compressions/vibration
 nerve surrounded by onion
like exterior
 decr. NA+ resistance
when bent… effect?
 Meissner- responds to
low frequency vibes
Ruffini-
stretch of skin..
Krause’s end bulbs- soft
touch, lips? Genital?
Slide 5: Spinal Nerves: Sending SS to brain
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Touch info below head enters brain
through spinal nerves (above head
through the crainial nerves)
31 set of Spinal nerves
Each set corresponds to a skin
sensory area called “Dermatomes”
As nerve info enters brain, heads
toward the SS cortex it divides into
specific paths handling different
sensory info (deep pressure,
touch.)
 recall laminae of the cortex (particularly
layer IV for sensory info)
Slide 6: PAIN- a healthy signal!
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Pain- multiple sensations
Carried by unmyelinated or thinly myelinated
axons to spinal cord (dull- thin axons, sharp- fat)
 what does this anatomic difference tell you about the nature of the
neural transmission of pain signals?
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Release the NTR: Substance P & glutamate
 moderate-glutamate
 intense-glutamate and substance P
– prolonged exposure-- tends to desensitize
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Capsaicin- mimics substance P
 “Ben Gay-like” applications
 These are not really painful applications, so how are they working?
Gate Theory of Pain- Melzack & Wall (1965)
Why do we rub the “boo-boo” to make it better
because it works!! But why does it work though
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Gate Theory- why non-pain stimuli reduce pain.
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The spinal cord is an area of congregation of multiple
sensory signals, but can only handle limited number
simultaneously-- after that… THE GATE CLOSES.
Transcutaneous Electrical Nerve Stimulation (TENS)
 example of TENS unit
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Accupuncture? (w/ Electrical Stimulation or heat stimulation)
Slide 8: Reducing Pain- Physiology
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Analgesic drugs - reduce pain- (“analgesia”)
e.g., Opiates like morphine-decrease substance P activity
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Regulation of pain through opioid systems
periaqueductal grey
endorphins inhibit substance-P release
 enkephalin & leuenkephalin
opiate systems share space in brain with areas that release
substance P.
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Dull pain vs. Sharp Pain
larger cell bodies (sharp) apparently less affected by
endorphin activity than smaller cell bodies (dull).
Slide 9: Chemical Senses
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Chemical Sensitivity- The most basic sensory system
primitive/single celled organisms to make critical survival
“decisions” about
 eating (poisonous or not); mating (finding, signaling)
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In humans, major chemical sensitivities refer to
Taste & Smell (Olfaction)
Experiencing change in the Chemical Senses
Label-line principle- receptors respond to a limited range of stimuli
and send direct line to brain.
Across-fiber pattern principle- receptors respond to range of stimuli
and contribute toward an overall experience. Combined pattern of
response = our experience (most vertebrate experience sense most
stimuli in this manner)
Slide 10: TASTY!
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Taste buds- areas in the papillae containing 2050 taste receptors sensitive to certain chemical
information (taste qualities).
[exper]
 Short life- 10-14 days.
 Aggregated in tip, back, & sides (not middle).
Slide 11: Taste Receptors
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Strong evidence for presence
of 4 distinct dimensions of taste
located somewhat discrete
locations.
1) taste adaptation
 adaptation to one taste (e.g., sour)
leads to decreased sensations of later
sourness.
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2) No cross-adaptation
 adaptation of one taste (sweet) does
not affect another (salty).
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Taste- carried by 3 crainial
nerves to NTS in brain
 helps to code meaning of taste
(function,need).
 Gatorade after workout.
Chemical Senses-Coding Taste
Mechanisms & Patterning
INOTROPIC EFFECTS
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Saltiness- receptor membrane salty receptors permeable to sodium
(NA+) leading to excess positive ions in neuron and subsequent AP.
Sourness- receptor at sour receptors prevent K+ release when an
acidic substance binds to the receptor leading to excess positive ions
in cell and subsequent AP.
METABOTROPIC EFFECTS
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Sweetness & Bitterness- effect G-Protein action when substance
binds to the receptor.
 Absence of this protein, absence of these tastes.
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KEY POINT: Buds sensitive to non-primary tastes ALSO, not
completely discrete. Supports patterned principle.
Chemical Senses
OLFACTION- Structure
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Olfactory Bulb
Olfactory Nerve
Olfactory Nerve Axons
Nasal Cavity
Olfactory receptor cell
Supporting cells
Olfactory Cilia
Chemical Senses
Many Olfactory Receptors
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Hundreds (Thousands?) of olfactory receptor types
may exist.
Many similar receptor “families” with slightly different amino acid
compositions
 therefore responsive to different odorant molecules.
Effect, we smell with greater precision
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Why so many? Not that way with sight (3 receptors)
Independence of chemistry of smell
 light - change in wave length, smell, completely different
particles
 space- receptor take up space, more types more room
needed.
The Chemical Senses
Vomeronasal Sensation and Pheromones
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Pheromones are chemicals
released by an animal that affect
the behavior of other members of
the same species
Human body secretions have
subtle pheromone effects
The human vomeronasal organ
This organ detects certain chemicals, especially
those found on the human skin, but produces no
conscious experience. Perhaps for that reason,
researchers were slow to discover this organ.
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