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Smell and Taste


									Smell, Taste, and Touch
Smell and Taste
   Why do we study smell and taste
• SENSORY INTERACTION: the principle
  that one sense may influence another.
  How do we taste?
•Taste (and smell) are
chemical senses.

 What is the central muscle
 involved in taste?
• Chemical sense composed of 4 basic
  senses: sweet, salty, sour, bitter
• Taste receptors (taste buds) regenerate
  every 1-2 weeks
• Each “bump” on tongue contains 200 taste
• Those bumps on our
  tongue are called
• Papillae help grip
  food while your teeth
  are chewing. They
  also have another
  special job - they
  contain your taste
                     Taste Buds

Map out the tongue
              Taste cont.
• Each bud contains a pore that catches
  food chemicals
• Molecules sensed by taste receptors
• Age, smoking, alcohol will lower taste bud
  number and sensitivity
          Smell (Olfaction)
• Inhale and exhale 20,000 times per day
• Nostrils fill with scent laden molecules
• Smell is a chemical sense – molecules of
  a substance reach the 5 million receptor
  cells in nasal cavity
• Olfactory receptor cells respond
  selectively and alert the brain
                Smell cont.
• Information directly transmitted to our
  temporal lobe – only sense that doesn’t
  first go through thalamus
• “hotline” between olfactory cortex and
  limbic system (memory & emotion)
  – Smell is a primitive sense
               Smell cont.
• How olfactory receptors work is a mystery
  – no distinct receptors for each odor
  – Triggers combination of receptors that our
    olfactory cortex interprets
  – We can recognize 10,000 different odors
              Smell cont.
• Ability to identify scents peaks in early
• Very good at discriminating scents but not
  good at describing them
• Odors have the power to evoke memories
  and feelings
      Gender related odors
• Can you smell the difference between?

So can we smell the difference?
• Well….yes and no.
•Chemical messengers that are picked up
through our sense of smell.
•Founded in the early 1930’s by studying
•Jury is still out on whether they exist in
humans. Best evidence we have comes out
of the university of Chicago.
• Composed of 4 senses: warmth, pain,
  cold, pressure (the only sense with
  identifiable receptors)
• Combinations of these create amazing
  – warmth and cold = hot
  – cold and pressure = wet
  – pressure and pain = tickling itch
             Touch - Pain
• Gate-Control Theory – spinal cord has
  “gates” that open/close to transmit pain
• Spinal cord has small fibers (transmit pain
  messages) & large fibers (transmit most
  other sensory signals)
  – Small fibers OPEN gates = PAIN
  – Large fibers CLOSE gates = NO PAIN
              Touch - Pain
• Pain memories – people overlook pains
  – “snapshot” of peak pain and then pain at the
             Touch - Pain
• Pain is merely a physical and
  psychological interpretation
• Distraction methods – attention is focused
  elsewhere – can ease the pain felt -
  Lamaze Childbirth Method
• Acupuncture(gate-control), electrical
  stimulation, and exercise can relieve pain
          Kinesthetic Sense
• System for sensing the position and
  movement of individual body parts
• Relies on sensors in muscles, tendons
  and joints
• Ex. – body parts “falling asleep” – nerve
  temporarily stops transmitting kinesthetic
           Vestibular Sense
• System for sensing body orientation and
  balance, located in the fluid filled
  semicircular canals of the inner ear
• Ex. – spin in circles until dizzy – after you
  stop spinning the fluid continues to spin –
  you are dizzy until the fluid stops spinning

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