Smell and taste LO1

Question 1

Receptors

Answer 1

• mechanoreceptors – respond to stretch, bend or deformation (hearing
  and balance)
• photoreceptors - contain molecules that respond to light (vision)
• chemoreceptors – respond to chemicals (smell and taste)

Question 2

Olfaction

Answer 2

• olfactory sensory neurons have cilia surrounded by mucus
• odorant must be volatile (gaseous)
• odorants must reach olfactory epithelium and dissolve in mucus
• odorant then binds and opens gated channels to generate an action potential

Question 3

The Olfactory Pathway

Answer 3

• olfactory sensory neurons form olfactory nerve (CN I)
• action potentials travel to olfactory cortex of temporal lobe
• information takes 2 pathways:
  1. to frontal lobe: smell consciously interpreted and identified
  2. to hypothalamus and other regions of limbic system:
  emotional responses to odour elicited

Question 4

Role of nose and smel

Answer 4

• nociceptors: detect pain
• thermoreceptors: detect temperature
• smells can also signal danger such as smoke or gas
• trigger a fight or flight response via sympathetic NS
• smell can offer protection by triggering sneezing and choking in
  response to unpleasant odours
• appetising smells can stimulate salivation and digestive system

Question 5

Gustation (Taste)

Answer 5

• provided by the gustatory epithelial cells in taste buds
• gustatory epithelial cells have microvilli called gustatory hairs
• food chemical must be dissolved in saliva
• food chemical binds to the receptor of the hair cells
• action potential is generated

Question 6

Gustatory Pathway

Answer 6

• Facial (VII), Glossopharyngeal
  (IX) and Vagus (X) carry action potentials
  from taste buds to
• gustatory cortex of the insula
• hypothalamus and limbic system (appreciation of
  taste)

Question 7

Role of mouth and taste

Answer 7

• taste sensations
• nociceptors: detect pain
• thermoreceptors: detect temperature
• triggers reflexes involved in digestion
• increase secretion of saliva into mouth
• increase secretion of gastric juice into stomach
• may initiate protective reactions
• gagging
• reflexive vomiting