Chapter Seven modules 2

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Chapter Seven- modules 2 37.2 The Mechanical
Senses7.3 The Chemical Senses
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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 movement-
• stretch receptors stretch reflexes
• This Chapter
• somatosensation touch, pain, temperature
• vestibular sensation position and movement of
  head (leads to corresponding adjustments in
  posture, eye movements)

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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

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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 bodys
  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..
• Krauses end bulbs- soft touch, lips? Genital?

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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)

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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?

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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)

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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).

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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)

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Slide 10 TASTY!

• Taste buds- areas in the papillae containing
  20-50 taste receptors sensitive to certain
  chemical information (taste qualities).
  exper
• Short life- 10-14 days.
• Aggregated in tip, back, sides (not middle).

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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.

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Chemical Senses-Coding TasteMechanisms
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.

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Chemical SensesOLFACTION- Structure

• Olfactory Bulb
• Olfactory Nerve
• Olfactory Nerve Axons
• Nasal Cavity
• Olfactory receptor cell
• Supporting cells
• Olfactory Cilia

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Chemical SensesMany 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.

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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.
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Slide 16
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Phantom Limb SensationSomatosensory Cortexs
Trick

• Intact Cortex, but loss of peripheral part
• amputation- often report feeling limb, an itch,
  even pain.
• After loss, cortex reorganizes connections
  association with new peripheral areas, often old
  connection remain
• stimulation of new area feel as if old
  (amputated) area is affected.
• Novel treament mirror images
• visual experience, plus presumed tactile
  reorganization. manipulating hand in mirror
  leads to experience of relief