physiology of smell and taste

Question 1

what causes taste and smell

Answer 1

chemoreceptors stimulated by binding to a particular chemical

Question 2

what does stimulation of taste and smell cause

Answer 2

• checkpoint for quality control
• influences the flow of digestive juice
• taste influenced by smell

Question 3

where are the sensory receptor cells of taste

Answer 3

in taste buds

Question 4

what do taste buds consist of

Answer 4

sensory receptor cells and support cells

Question 5

where are majority of taste buds

Answer 5

papillae of tongue

Question 6

what are the four types of papillae

Answer 6

• filliform (no taste buds)
• fungiform
• vallate
• foliate

Question 7

what is the physiology of taste

Answer 7

• binding of taste provoking chemical to receptor cells produces depolarising receptor potential
• receptor potential initiates action potentials in afferent nerve fibres which synapse with receptor cells
• signals conveyed by cranial nerves to cortical gustatory areas in brain

Question 8

which cranial nerves do the afferent taste fibres reach the brain stem via

Answer 8

• VII (chorda tympani branch of facial nerve)
• IX (glossopharyngeal)
• X (vagus)

Question 9

what is ageusia

Answer 9

loss of taste function

-can be caused by nerve damage, inflammation, endocrine disorders

Question 10

what is hypogeusia

Answer 10

reduced taste function

Question 11

what is dysgeusia

Answer 11

distortion of taste function

-caused by glossitis, gum infections, resp problems etc

Question 12

what are the four neural systems in the nose

Answer 12

• main olfactory system (cranial nerve I)
• trigeminal somatosensory (CN V)
• accessory olfactory
• nervus terminalis (CN 0)

Question 13

what must a substance be to be smelled

Answer 13

• sufficiently volatile

- sufficiently water soluble (can dissolve in mucus coating of olfactory mucosa)

Question 14

how do we smell

Answer 14

• odour must enter nose
• pass to olfactory cleft
• move from air phase to aqueous phase
• bi-polar sensory neuron extends odourant receptor-containing cilia into mucus
• supporting cells insulates and protects
• duct cell of bowmans glands secretes mucus
• basal cells

Question 15

how does smell reach brain

Answer 15

olfactory nerves pierce through cribriform plate and enter the olfactory bulbs
-from olfactory bulb neurons pass along the olfactory transmit to reach the temporal lobe and olfactory areas

Question 16

abnormalities in smell

Answer 16

anosmia - inability to smell
hyposmia - reduced ability to smell
dysosmia - altered sense of smell
phantosmia - smell perceived in teh absence of stimulus

Question 17

conductive causes of abnormality in smell

Answer 17

• nasal polyps
• rhinitis
• nasal mass

Question 18

sensironeural causes of abnormal smell

Answer 18

• viral
• head trauma
• neurological conditions
• brain tumours
• medications