How do we Stay Balanced?

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How do we Stay Balanced?

• The Vestibular System

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Vestibular System (Balance)
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Vestibular System (Balance)
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Vestibular System (Balance)
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Vestibular System (Balance)
Head accelerates this way
Fluid goes this way
Cupula gets pushed
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Vestibular System (Balance)
Fluid goes this way
Head accelerates this way
Cupula gets pushed
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Vestibular System (Balance)

• movement of the cupula is detected by hair cells
• hair cells in the vestibular system are more
  sensitive than hair cells on the basilar membrane!

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Vestibular, Visual, and Proprioceptive Systems
Work Together

• Try standing on one foot with your eyes closed!

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Fun Facts about The Vestibular System

• Seasickness arises when the vestibular system and
  the visual system send conflicting information

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Fun Facts about The Vestibular System

• Seasickness arises when the vestibular system and
  the visual system send conflicting information
• People can be knocked down by moving walls!

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Fun Facts about The Vestibular System

• Seasickness arises when the vestibular system and
  the visual system send conflicting information
• People can be knocked down by moving walls!
• Alcohol causes the spins by (among other things)
  changing the density of the fluid in the
  semicircular canals

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Sensory Systems

• Touch, temperature, taste, smell

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There are a variety of touch receptors
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• Touch receptors send signals to the somatosensory
  cortex via long axons in the spinal cord
• Signals are sent to the opposite (contralateral)
  side of the brain

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The Homunculus

• Wilder Penfield - Montreal Neurological Institue
  - 1940s
• Found somatotopic map by stimulating brain during
  surgery

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Thermoception

• Two classes of thermoreceptors warm and cold

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Taste (Gustation)
Taste buds contain chemical receptors
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Taste
What are the various tastes?
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Taste

• Multi-dimensional scaling reveals several
  varieties of tastes
• sweet
• salt
• bitter
• sour
• umami (MSG) - possibly a protein receptor
• there may also be a lipid (fat) receptor

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Smell

• Olfactory bulb receives input from olfactory
  receptors which contact mucus in nasal cavity

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Smell

• There are thousands of different receptors for
  different kinds of molecules

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Smell

• Olfactory receptors use a lock-and-key
  mechanism - only specific molecules will bind
  with a given receptor

Odor Molecules
Receptor
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Smell

• Odor recognition is excellent in humans
• but odor identification (naming) is very poor
• Women tend to be (slightly) better than men at
  naming smells

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Smell

• Smell is strongly influenced by top-down
  processes such as what you are expecting to smell

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Pheromones

• Pheromones are not smells
• Pheromones are chemical signals sent from one
  animal to another

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Pheromones

• Pheromones either induce a behavior in another
  animal or cause some physiological change
• Very common in insects...not so common in
  mammals...unclear role in humans

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Fun Facts about Pheromones

• For example Androstenone, found in male pig
  saliva, causes a female pig to allow the male to
  mate with her

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Fun Facts about Pheromones

• androstenone is also found in the sweat of human
  males!
• Does androstenone (or pheromones in general)
  affect humans?
• Design an (ethical) experiment

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Fun Facts about Pheromones

• Kirk-Smith Booth (1980) sprayed some of the
  seats in a dentists waiting room with
  androstenone
• Compared to a control condition, more women used
  the androstenone seat

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Fun Facts about Pheromones

• Fewer men used the androstenone seat !

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Pheromones

• Other possible ways in which pheromones influence
  humans
• synchronization of menstrual cycles
• mate selection - attraction to opposite major
  histocompatibility complex

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Pheromones

• Pheromones do not control behavior!
• Human behavior is largely under top-down
  influences, but may be affected subtly by
  pheromones
• It is unclear whether molecules such as
  androstenone even qualify as pheromones - they
  may be just like other odour molecules