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
The Mechanical Senses
senses responsive to change in pressure, bending, or other structural
change in a receptor
Past Chapter on movementstretch receptors & stretch reflexes
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
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
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
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!
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?
Release the NTR: Substance P & glutamate
moderate-glutamate
intense-glutamate and substance P
– prolonged exposure-- tends to desensitize
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
Gate Theory- why non-pain stimuli reduce pain.
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
Accupuncture? (w/ Electrical Stimulation or heat stimulation)
Slide 8: Reducing Pain- Physiology
Analgesic drugs - reduce pain- (“analgesia”)
e.g., Opiates like morphine-decrease substance P activity
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.
Dull pain vs. Sharp Pain
larger cell bodies (sharp) apparently less affected by
endorphin activity than smaller cell bodies (dull).
Slide 9: Chemical Senses
Chemical Sensitivity- The most basic sensory system
primitive/single celled organisms to make critical survival
“decisions” about
eating (poisonous or not); mating (finding, signaling)
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!
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
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.
2) No cross-adaptation
adaptation of one taste (sweet) does
not affect another (salty).
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
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
Sweetness & Bitterness- effect G-Protein action when substance
binds to the receptor.
Absence of this protein, absence of these tastes.
KEY POINT: Buds sensitive to non-primary tastes ALSO, not
completely discrete. Supports patterned principle.
Chemical Senses
OLFACTION- Structure
Olfactory Bulb
Olfactory Nerve
Olfactory Nerve Axons
Nasal Cavity
Olfactory receptor cell
Supporting cells
Olfactory Cilia
Chemical Senses
Many Olfactory Receptors
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
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
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.
Slide 16: