DSA 1: Neuroanatomy of Gustation and Olfaction

Question 1

What are the four basic tastes?

Answer 1

Sweet
Salty
Sour
Bitter

Question 2

How do we recognize many different tastes other than the basics?

Answer 2

Few taste receptors in different combinations result in different taste sensations.

Question 3

Where are olfactory bulbs found?

Answer 3

Cribiform plate of ethmoid bone

Question 4

What does the olfactory tract do?

Answer 4

Transmit sensory information from the environment to the brain

doesnt pass thru thalamus

Question 5

Where are olfactory receptor neurons (ORN) found?

Answer 5

Roof of nasal cavity

Inferior surface of cribiform plate along the nasal septum and medial wall of superior turbinate

Question 6

How many dendritic processes does the olfactory receptor neuron (CN 1) have?

Answer 6

SINGLE dendritic process

Question 7

What type of receptors are odorant receptors?

Answer 7

GPCR

Question 8

what are the components of olfactory histology

Answer 8

1. lamina propria
2. basal cells
3. olfactory receptor neurons
4. supporting cells
5. brush cells
6. cilia
   7 mucosa

Question 9

what does the lamina propria contain

Answer 9

CT w/ immune cells

= exposed to the outside

Question 10

what are basal cells

Answer 10

layer underneath basement mem
=stem cells & supporting cells

-continuous turnover (30-60 days)

Question 11

what is the histological representation of brush cells

Answer 11

ciliated columnar epithelial cilia

Question 12

what are cilia of the epithelium

Answer 12

= nonmotile

contain GPCR odorant receptors that signal to bulbs

Question 13

what does the mucosa do

Answer 13

hold ORNs

made & secreted by glands & ducts

Question 14

how many receptors do ORNs project to?

Answer 14

only 1 odorant receptor

but a receptor can get multiple inputs

Question 15

why are ORNs sensitive to damage with facial trauma

Answer 15

bc of thin bone

Question 16

how do you sense so many different smells

Answer 16

• ORN able to recognize over 1,000 odorants at small concentrations
• diff combinations of activation –> sense diff smells

Question 17

what do the olfactory bulbs contain

Answer 17

receptor maps

Question 18

what is olfactory epithelium

Answer 18

gland & ducts for nasal moisture

-carry info to specific areas of the bulb (receptor map)

Question 19

what are the layers of the olfactory bulb

Answer 19

1. olfactory N layer: axons of ORN
2. glomerular layer: ORN synapse on mitral/tuft cells
3. external plexiform layer: dendrites of mitral/tuft/granule cells
4. mitral cell layer: mitral cell bodies & tuft axons
5. granule cell layer: granule cells, principle interneurons of bulbs

Question 20

what are the steps of olfaction

Answer 20

1. odorant contact mucosa & bind GPCR –> adenylyl cyclase –> cAMP –> bind ion channels –> increase Na & Ca influx –> depol/AP –> use ORN to go to bulb
2. ORN synapse w/ mitral/tuft cells
3. lateral olfactory tract use mitral/tuft cells to get to olfactory cortex (fibers of ant limb of ant commissure)

Question 21

what are centrifugal fibers

Answer 21

reach bulb via ant commissure

stimulate granule cellls –> (indirectly) decrease mitral/tuft w/ GABA

Question 22

what are periglomerular cells

Answer 22

inhibit mitral/tuft cells

-help adjust to smell

Question 23

what does the olfactory cortex do

Answer 23

project to other areas of brain

-paleocortex

Question 24

how do thalamic nuclei affect smell

Answer 24

help discriminate & identify smell

Question 25

what is the purpose of the orbitofrontal cortex in olfaction

Answer 25

integrate olfaction, taste & other food cues to help experience flavor

Question 26

where do olfactory tract fibers project to

Answer 26

1. hippo : learn/mem
2. lat. hypothal: feeding behavior
3. amydgala: identify danger/fear
4. ant olfactory nuclei: send info back to bulb & other areas of cortex
5. dorsomedial thalamic nuclei: further processing (NOT REQUIRED)

Question 27

what is anosmia

Answer 27

loss of smell

Question 28

hyposomia (olfactory hypesthesia)

Answer 28

decrease sensitivity to odorants

ex: nasal polyps in nasal cavity/sinus

Question 29

ageusia

Answer 29

complete loss of taste

Question 30

hypoguesia

Answer 30

decrease taste sensitivity

Question 31

paraguesia/dysgeusia

Answer 31

alter taste perception

could be from drug use

Question 32

tumor of internal acoustic meatus

Answer 32

loss of ipsi 2/3 of ant tongue

Question 33

distal genticulate ganaglion

Answer 33

may/may not affect taste

-ipsi paralysis

Question 34

what are taste buds

Answer 34

sensory organs all throughout oral cavity/pharynx

located in soft palate (innervated by greater superficial petrosal N)

Question 35

which taste buds are innervated by CN 9

Answer 35

villate papillae

posterior foliate papillae

Question 36

which taste buds are innervated by CN 10

Answer 36

epiglottis

esophagus

Question 37

what is taste reception

Answer 37

soluble chemicals that diffuse through taste pores

-chemicals bind on apical microvilli

Question 38

what is the significance of the pontomedullary jxn for gustation

Answer 38

afferent CN 7 carry chorda tympani

• innervate ant 2/3 of tongue (ant. foliate papillae & fungiform papillae)

Question 39

what is the path for gustation sensation

Answer 39

sensory cell bodies in geniculate ganglia (CN 7 afferents) –>

carry taste via solitary tract to rostral solitary nucleus –>

2nd order neuron via IPSI central tegmental tract to paricellular VPM –>

3rd order neuron thru IPSI post limb of IC to frontal operculum & ant. insular cortex –> then to rostral Broadmann area 3b (in post central gyrus)