exam 2: Lecture 20 Chemical sense (smell and taste)

Question 1

what are the chemical senses?

Answer 1

taste and smell

Question 2

how does smell work?

Answer 2

cilia on the bottom of the mucosal layer send the signal to the dendrites of the olfactory sensory neuron and then their axons go to the olfactory bulb
- the olfactory bulb projects to the olfactory cortex and this projects to the orbitofrontal cortex

Question 3

what do odor receptors respond to?

Answer 3

only 1 type of molecule
- molecules may trigger many different receptors at one time

Question 4

how many odorant receptors do humans have?

Answer 4

only 400
- each type receptor is confined to confined to certain regions of the nasal epithelium

Question 5

what is the bone that the axons of the nasal cavity project through?

Answer 5

the cribriform plate

Question 6

glomeruli?

Answer 6

tangled bits of dendrites of relay neurons in the olfactory bulb which project to olfactory relay neurons going to the olfactory cortex

Question 7

olfactory relay neurons do what?

Answer 7

relay smell information to primary olfactory cortex right above the eyes and then the orbitofrontal cortex just behind primary olfactory cortex
- examples are turfed and mitral cells

Question 8

how many glomeruli are there in the olfactory bulb?

Answer 8

800 because there are 2 glomeruli for every odor receptor in the nasal epithelium

Question 9

what 2 places does the olfactory bulb project to?

Answer 9

1. the olfactory cortex project to orbitofrontal cortex just above the eyes and allows odor discrimination in humans
2. project to lateral hypothalamus involved with appetite

Question 10

pheromones

Answer 10

special class of odorants that can modulate levels of reproductive hormones
- Can elicit aggression or sexual behavior
- Often found in urine or glandular secretions
- not yet clear if humans have this

Question 11

general anosmia

Answer 11

inability to smell

Question 12

2 types of general anosmia?

Answer 12

traumatic from a blow to the head or transient from respiratory infections

Question 13

specific anosmia

Answer 13

inability to smell specific odorants
- common and genetic

Question 14

5 taste senses

Answer 14

• Sweet
• Umami ⇒ flavor of amino acids
• Salty
• Sour
• Bitter

Question 15

what taste senses are appealing and not appealing to people?

Answer 15

appealing: sweet and umami
aversive: sour and bitter

Question 16

taste

Answer 16

results from the activation of the 5 receptors

Question 17

flavor

Answer 17

complex sensation resulting from the mixing of taste with smell and somatosensation

Question 18

what 3 cranial nerves are involved with taste?

Answer 18

1. facial CN7 => anterior 2/3
2. glossopharyngeal CN9 => posterior 1/3
3. Vagus CN 10 ==> epiglottis and posterior oropharynx

Question 19

papillae and 3 types?

Answer 19

where most of the taste buds are located
- circumvallate
- foliate
- fungiform

Question 20

circumvallate taste buds

Answer 20

on the very back of your tongue relating to glossopharyngeal nerve

Question 21

foliate taste buds

Answer 21

on the posterior lateral part of your tongue relating to facial nerve

Question 22

fungiform taste buds

Answer 22

on the lateral middle and front of your tongue relating to the facial nerve

Question 23

what are taste buds innervated by?

Answer 23

gustatory afferent neurons have their terminal innervating the base of the tastebud
- leading to only one of the 3 cranial nerves

Question 24

what do taste receptors act like?

Answer 24

they act like neurons and can have action potentials + release a neurotransmitter onto the terminal of the nerves

Question 25

what do T1 receptors relate to?

Answer 25

sweet and umami taste receptors - these are a dimer with 2 proteins in them

Question 26

what do T2 receptors relate to?

Answer 26

bitter taste receptors

Question 27

what taste senses have gated ion channels for either sodium or sodium and hydrogen?

Answer 27

salt (Na+) and sour (Na+; H+)

Question 28

what kind of receptors do fungiform papillae have?

Answer 28

T1 receptors for umami taste

Question 29

what kind of receptors do circumvallate papillae have?

Answer 29

T1 receptors for sweet taste

Question 30

what kind of receptors do foliate papillae have?

Answer 30

T2 receptors for bitter taste

Question 31

does taste project contralateral or ipsilateral?

Answer 31

ipsilateral and everything else is contralateral

Question 32

what tract do taste sensations enter and where?

Answer 32

they enter the solitary tract in the rostral medulla

Question 33

what is the pathway for taste to the brain?

Answer 33

receptor --> solitary tract --> ventral posterior medial thalamus --> gustatory cortex (insula)

Question 34

ageusia and partial ageusia

Answer 34

loss of sense of taste and loss of a particular taste

Question 35

dyspepsia

Answer 35

constant unpleasant metallic taste in mouth

Question 36

how does loss of taste occur?

Answer 36

from damage to chorda tympani; branch of the facial nerve responsible for taste in anterior tongue