olfaction and gustation(theory)

Question 1

what is the purpose of the olfactory glands?

Answer 1

to secrete mucous to dissolve odorants in the air for the hair cells to receive

Question 1

what does the olfactory epithelium consist of?

Answer 1

1. olfactory receptors
2. supporting cells
3. basal cells
4. olfactory glands

Question 2

where does the olfactory nerve (CN I) end?

Answer 2

at the olfactory bulb

it contains mitral cell body neurons that run down the olfactory tract and are connected the olfactory epithelium (hair cells)

Question 3

what do the olfactory hair cells pass through?

Answer 3

they pass through the olfactory foramina of the cribriform plate of the ethmoid bone

Question 4

what can damage the olfactory neurons

Answer 4

some chemicals may damage olfactory neurons but they can regenerated by the basal cells

Question 5

olfactory cilia

Answer 5

part of epithelium and are extensions of the olfactory receptors cells

cilia extend into the mucous layer

Question 6

what can dryness do to olfaction?

Answer 6

dryness can affect our sense of smell

Question 7

olfactory pathway

Answer 7

1. odorant stimulates olfactory hair cell
2. axons of the olfactory epithelium pass through the cribriform plate
3. olfactory epithelium axon synapses on neurons of the olfactory bulbs
4. impulse travels up CN I
5. arrive at the cerebral cortex (insula)
6. hypothalamus
7. limbic system

Question 8

how many different smells can humans differentiate?
how is this possible?

Answer 8

humans can recognize over 1 trillion smells

this is possible because our olfactory receptors have varying sensitivity to different smells

Question 9

what is the main muscle involved with gustation (taste)

Answer 9

the tongue, it has papillae which is made up of taste buds

Question 10

what are the 3 types of taste buds

Answer 10

1. filifrom
2. fungiform
3. circumvallate

taste buds are classified by shape and distribution across the tongue

Question 11

what cranial nerves supply the tongue?

Answer 11

1. CN VII
2. CN IX

Question 12

where are the filiform taste buds?

Answer 12

the tip of the tongue

Question 13

where are the fungiform taste buds?

Answer 13

the sides of the tongue

Question 14

where are the circumvallate taste buds?

Answer 14

towards the back of the tongue

Question 15

what are the 4 (sometimes 6) kinds of taste the tongue can perceive?

Answer 15

1. sour
2. sweet
3. bitter
4. salty
5. umami
6. water

Question 16

what are taste buds made of?

Answer 16

they are made of gustatory cells

gustatory cells have microvilli which pick up the dissolved chemicals of the stimulant

gustatory cells fire an impulse to the CNS to interpretation of the taste

Question 17

what cranial nerves do the gustatory cells fire on?

Answer 17

1. CN VII –> facial
2. CN IX –> glossopharyngeal
3. CN X –> vagus

Question 18

what gets synapsed onto by the cranial nerves? (order of synapse series)

Answer 18

1. nucleus solitarius of the medulla
2. medial lemniscus
3. thalamus

there is cross over at the medial lemniscus of the medulla

Question 19

where does sensory info from the gustatory cells end up?

Answer 19

in the gustatory cortex of the insula

Question 20

do we have taste buds of the epiglottis?

Answer 20

yes we do, this is so the epiglottis can sense if food is trying to make its way into the larynx and therefore it closes

Question 21

gustatory discrimination

Answer 21

• 10,000 taste buds
• can be regenerated but we still lose them as we age
• low threshold for unpleasant stimuli
• high threshold for pleasant stimuli