special senses (taste and olfaction) Flashcards

1
Q

what is olfaction

A
  • chemoreceptors respond to smell similar to taste

- chemicals dissolve in mucous of nasal passages before binding to chemo. and registered as ‘smell’ by brain

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2
Q

how does olfaction differ between humans and domestic animals

A
  • superior olfactory ability

- greater SA of nasal cavity lining and size of olfactory region in brain

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3
Q

what is the pathway of the olfactory nerves

A
  1. nasal mucosa - olfactory epithelium
  2. through cribriform plate of ethmoid bones
  3. synapse at glomeruli from olfactory bulbs to mitral cells
  4. olfactory tract to limbic system / primary olfactory cortex
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4
Q

describe the anatomy of the nasal cavity

A
  • ciliated pseudo stratified epithelium
  • 3cm^2, olfactory cilia located on dendrites of sensory neurons
  • nocic and temp receptors (ammonia, chilli)
  • 1000 smell genes in nose (super sensitive)
  • stronger smell = more odour molecules
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5
Q

how are AP generated in the nasal cavity

A
  1. odourant molecules dissolve and cross mucosal layer
  2. bind to receptor coupled with G protein
  3. activates G protein, cascade of events
  4. influx of Ca and Na = depolarisation (decreases potential from -55 to -30)
  5. AP
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6
Q

describe the anatomy of papillae and tastebuds

A
  • P: rounded protuberance on tongue, contain tastebuds

- TB: most respond to 2-4 taste qualities, bitter = most sensitive (protection), sugar / slat = pleasurable

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7
Q

describe the receptors present in the mouth and pathways

A
  • adapt quickly
  • localisation = some regions more sensitive to certain tastes than others
    1. selectively bind to chemicals in food
    2. opening / closing of ion channels
    3. changes in electrical potential
    4. increase in Ca = neurotransmitter
    5. afferent nerve stimulated
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8
Q

briefly describe the gustatory pathway to the brain

A
  1. release of neurotransmitter AP
  2. facial nerve (anterior 2/3 tongue) or glossopharyngeal nerve (posterior 1/3 tongue) or vagus nerve (back of mouth)
  3. all travel to solitary nucleus of medulla
  4. initiates PsNS reflexes (saliva / gastric secretion)
  5. thalamic nucleus to gustatory cortex (parietal lobe) and limbic system
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