DSA Neuroanat. Of Gustation And Olfaction Flashcards

1
Q

What makes olfactory receptor neurons very sensitive?

A

Thin nasal bones

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2
Q

What do olfactory receptor neurons recognize?

Allows for role in what?

A

Recognize 1000s of airborne odors

Role in pleasure assoc. w/ eating and in recognizing environments

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3
Q

What are the 4 basic tastes?

Fifth?

A

Sweet
Salty
Sour
Bitter

Umami

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4
Q

What recognizes a wider variety of sensations?

Nose or tongue?

A

Nose

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5
Q

What is the sensation of Umami important for?

A

ID of Amino Acids

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6
Q

How do we perceive different tastes?

A

Different combos of taste receptors

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7
Q

How does smell get transmitted to brain?

A

Smell —> filtered thru nostrils —> back of nose —> Olfactory epithelium —> olfactory receptor cells —> olfactory tract —> brain

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8
Q

What is unique about the olfactory epithelium?

A

Pigmented and we don’t know why

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9
Q

What is the only neuron that gets replaced regularly?

A

Olfactory receptor neurons

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10
Q

Where will the olfactory tracts make stops in the Brain?

A

Amygdala
Thalamus
Neocortex

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11
Q

What is the olfactory bulb for?

Where is it?

A

Helps humans smell

Lies in cribriform plate of ethmoid bone

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12
Q

What is the olfactory tract for?

A

Helps transmit sensory info from environment to the brain

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13
Q

Where is the cribriform plate?

A

Rostral end of olfactory sulcus and anterior cranial fossa

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14
Q

What helps keep the nasal cavity moist?

A

Ducts and gland of the olfactory epithelium

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15
Q

Where are the dendrites and receptors of the olfactory nerves?

A

Extended into the olfactory epithelium for good exposure to smell molecules

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16
Q

What are the layers of the olfactory epithelium, histologically?

A
Lamina propria
Basal cells
Olfactory receptor neurons
Supporting/sustentacular cellls
Brush cells
Cilia
Mucus
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17
Q

In the Olfactory Epithelium,

What is the lamina propria?
Role?

A

Layer of ct

Holds immune cells - important bc mucosa is directly exposed to external environment

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18
Q

In the Olfactory Epithelium,

What is the basal cell layer?
Role?

A

Cells next to basement membrane

Act as stem cells for ORNs and supporting cells
Will continuously turn over
Life span of 30-60 days

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19
Q

In the Olfactory Epithelium,

What is the Olfactory Receptor Neuron layer?
Role?

A

Cell bodies of nerve

Single dendrite will extend to mucus layer

Axons to olfactory bulb thru the lamina propria

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20
Q

In the Olfactory Epithelium,

What is the Supporting/Sustentacular Cell layer?
Role?

A

Cells that offer physical and metabolic support to surrounding cells

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21
Q

In the Olfactory Epithelium,

What are the brush cells?

A

Ciliated columnar epithelial cells

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22
Q

In the Olfactory Epithelium,

How would you describe the layer of cilia?

A

Non-motile

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23
Q

In the Olfactory Epithelium,

How is the mucus made?

A

Made and secreted by glands and ducts in OE

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24
Q

Where are olfactory receptor neurons located?

A

On roof of nasal cavity
Inferior surface of cribriform plate
Along nasal septum
On medial wall of superior turbinate

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25
Q

How many dendrites does CN1 have?

What does it do?

Where is its receptor?

A

Single dendritic process per neuron that receives info from environment

Receptor is in olfactory mucus of superior portion of nasal cavity

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26
Q

What is the purpose of the Cilia of Olfactory receptor Neurons?

A

Non-motile

Have odorant receptors (GPCRS-Golf) that will send signal to olfactory bulb

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27
Q

How is smell transmitted? (4 steps)

A
  1. Smell molecule —> mucus layer covering OE —> odorant binding proteins in mucus
  2. Binds GPCR (Golf) —> Adenyl cyclase —> increased cAMP
  3. Increased cAMP —> opens ion channels, allows influx of Na and Ca into cell
  4. Depolarization, AP —> neurons in Olfactory bulb
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28
Q

How is the olfactory epithelium organized?

A

In a receptor map, with different regions lining up and carrying info to specific areas of olfactory bulb

= initial step for olfactory discrimination

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29
Q

How are odors perceived?

A

Encoded by several different receptors are varying magnitudes

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30
Q

How does the Olfactory Epithelium make a Receptor map?

A

By preferentially distributed receptors int he olfactory epithelium

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31
Q

How many odor molecules can bind an olfacotry receptor neuron?

A

Only 1 type bc only 1 type of odorant receptor

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32
Q

What do the axons of the olfactory receptor neurons extend upwards thru?

In order to do what?

A

Cribriform plate (part of ethmoid bone) in order to synapse w/ the olfactory bulb

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33
Q

What are the 5 layers of the Olfactory bulb? (From olfactory tract to cribriform plate/OE)

(deep to superficial)

A
  1. Granule layer
  2. Mitral layer
  3. External Plexiform layer
  4. Glomerular Layer
  5. Olfactory Nerve Layer

“GRow My EGO”

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34
Q

How do centrifugal fibers reach the olfactory bulb?

What is their purpose?

A

Via anterior commissure

Help regulate feedback loops

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35
Q

What is the purpose of the olfactory tract?

A

Connects the bulb to the rest of the brain?

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36
Q

What are the components of the Olfactory tract?

A

Lateral olfactory tract

Cells of anterior olfactory nucleus

Fibers of anterior limb of anterior commissure

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37
Q

Where do afferent projections from olfactory receptor neurons synapse?

A

W/ mitral and tufted cells in olfactory glomerulus

38
Q

How many glomeruli can an Olfacotory Receptor neuron synapse in?

A

Just one

39
Q

How many Olfactory Receptor neurons can 1 glomerulus have synapsing with it?

A

Multiple

40
Q

What is the Glomerulus of the Olfactory bulb?

A

Receives axons from ORNs expressing SAME odor molecule specific receptors

41
Q

How many types of GPCRs will a glomerulus receive input from?

A

ONE TYPE

Bc receives info from multiple ORN axons for SAME odor (=SAME GPCR Type)

42
Q

What regulates the activity in the Glomerulus ?

A

Olfactory neurons receptors

Periglomerular cells

Mitral/Tufted Cells

Centrifugal fibers

43
Q

What do olfactory neuron receptors regulated?

A

Mitral/tufted cells

Periglomerular cells

44
Q

What do periglomerular cells regulate?

What is their role?

What regulates it?

A

Antagonize Mitral/tufted and olfactory receptor neuron cells

Role in getting used to smells by receiving input from ONRs and shutting down Mitral/Tufted

Olfactory receptor neurons

45
Q

What are mitral/tufted cells regulated by?

Role?

A

By olfactory receptor neurons

Receives info from ORNs in Olfactory Glomeruli (in olfactory bulb) and carries it thru olfactory tract to olfacotry cortex in brain

46
Q

What will constant stimulation of mitral/tufted cells result in?

A

Positive effect on granular cells

active granular —> inhibit mitral/tufted —> halt spread of info to olfactory cortex

= forget smells

47
Q

Besides constant stimulation of Mitral and Tufted cells, what else will have a positive effect on granule cells?

A

Centrifugal fibers

48
Q

What effects will centrifugal fibers have?

A

Active granule —> inhibit mitral/tufted cell activity

49
Q

What is the role of centrifugal fibers?

A

Carries efferent info FROM brain to olfactory bulb to react w/ granular cells to regulate mitral and tufted cells to help forget smell

50
Q

What do granular cells release in olfactory bulbs?

A

GABA to inhibit mitral/tufted cells and play role in forgetting about smells

51
Q

What are the 1st, 2nd, and 3rd order neurons in the olfactory pathway?

A

1st: ORN CN1 (—> olfactory bulb)
2nd: Mitral/tufted cell (info to olfactory cortex of brain, processed PRIMITIVELY)

3rd neuron:
(—> info to olfactory cortex in paleocortex
—> neocortex (thalamus, hippocampus, etc.)

52
Q

How is information carried form the olfactory bulb to the olfacotry cortex?

What tract and what cells?

A

Lateral olfactory tract

Via Mitral/Tufted cells

53
Q

What do projections pass thru on way to olfactory cortex?

A

NOTHING

GOES DIRECTLY TO OLF. CORTEX

Smell = primitive sense, does not synapse on brains structures

54
Q

What do zones in the OE correlate with?

A

Zones in the olfactory bulb

55
Q

What do zones in the olfactory bulb correlate with?

A

Nothing.

Olfactory corticies do not have correlating zones bc info from different zones of olfactory bulb can go to any region of cortices

56
Q

What is the lateral olfactory tract made of?

A

Axons of mitral/tufted cells

57
Q

What part of the amygdala is involved in correlating smell and fear?

A

Anterior cortical amygdaloid nucleus

58
Q

What is the role of the Neocortex in Olfaction?

A

Helps discriminate and identify odors

59
Q

What is the role of the dorsomedial Thalamic nucleus?

A

Further processing of afferent projection Via a secondary projection

(Smell is not relayed here for initial processing)

60
Q

What is the role of the hippocampus in olfaction?

A

Smells are associated with a memory

Secondary projections to the hippocampus allow for Long term processing

61
Q

What is the role of Orbitofrontal cortex in olfaction?

A

Helps integrate olfaction, taste and other food cues

Helps humans experience flavors and enjoy food

62
Q

What are the components of the olfactory cortex?

A

Anterior olfactory nucleus

Olfactory tubercle

Piriform cortex

Anterior cortical amygdaloid nucleus

Periamygdaloid cortex

Lateral entorhinal cortex (hippocampus)

63
Q

What is the result of this pathway?

Olfactory cortex —> lateral hypothalamus?

A

Body responds w/ appropriate feeding behavior

64
Q

What is the result of this pathway?

Olfactory cortex —> Hippocampus?

A

Input is linked to learning and behavior

65
Q

What are taste buds?

A

Sensory organs that can perceive experiences of sweet, salty, sour, bitter and umami

66
Q

Where are taste buds found?

A

Oropharyngeal cavity

Thru-out oral cavity and pharynx

67
Q

Where are taste buds most concentrated?

A

On tongue

68
Q

What does Chorda tympani innervate?

A

Fungiform papillae
Anterior foliate papillae

On anterior 2/3rds of tongue

69
Q

What is Chorda tympani a branch from? Where does it pass?

A

Cn 7

Thru middle ear

70
Q

How is the taste reception process initiated?

A

When soluble chemical diffuse thru taste pore and bind to receptors on apical microvilli of taste cells

71
Q

What does the Greater Superficial Petrosal N. Innervate?

A

Taste buds on soft palate

72
Q

If there is sufficient depolarization of taste receptors, what will occur?

A

AP to afferent fibers

Afferent fibers thru pontomedullary junction to brainstem

To Geniculate ganglia

73
Q

What comprises the Geniculate ganglia?

A

Sensory fiber cell bodies of CN 7

74
Q

Where will taste sensation go after the Geniculate ganglia?

A

Fibers of CN 7 carrying taste sensation synapse in Solitary Tract

& then to

Rostral Solitary nucleus

75
Q

What is another name for the Rostral Solitary nucleus?

A

Gustatory Nucleus

76
Q

What does CN 9 innervate in terms of Gustation?

A

Taste buds in vallate papillae and posterior foliate papillae

77
Q

What does CN10 innervate in terms of GUstation?

A

Taste buds of the epiglottis and esophagus

78
Q

How to fibers of CN 9 and 10 carry gustation info to brain?

A

Same pathways as CN 7

Afferent fibers —> pontomedullary junction
—> brainstem —> geniculate ganglia
—> solitary tract
—> rostral solitary nucleus (Gustatory Nucleus)

79
Q

What is Gustatory Sensory information responsible for?

A

Discriminating taste

80
Q

After reaching the Rostral Solitary nucleus, how does gustatory sensory info travel?

A

First synapse: in solitary tract/nucleus

2nd order neurons thru IPSILATERAL central tegmental tract

2nd Synapse: in VPMpc w/ 3rd order

3rd order neurons thru IPSILATERAL posterior limb of internal capsule

3rd synapse/Final Destination:
Anterior frontal operculum & Anterior Insular Cortex (AKA Rostral Area of Brodmann area 3b)

81
Q

Where do 2nd order neurons of the gustatory pathways synapse with 3rd order?

A

Parvicellular Ventral Posteromedial Nucleus (VPMpc)

82
Q

Where is the Rostral area of Brodmann area 3b?

A

In post-central gyrus

83
Q

Where can gustatory info go from Brodmann area 3b?

To do what?

A

Lateral posterior Orbitofrontal cortex

Take info and integrate it w/ vision
Gustation assoc. w/ Olfaction now

84
Q

What is anosmia?

A

Loss of smell

85
Q

What is hyposomia/olfactory hypesthesia?

Caused by?

A

Decreased sensitivity to odorants

Nasal polyps (non-cancerous growths in nasal cavity/sinuses)

86
Q

What is ageusia?

Why is this not commonly seen?

A

Complete loss of taste

Bc multiple nerves carry taste (CNs 7, 9, 10)

87
Q

What is Parageusia/Dysgeusia?

Due to?

A

Altered perception of taste

Drug use (prescription or recreational)

88
Q

What can cause lesions of CN 7 in the middle ear?

A

Tumor in IAM (vestibular schwannoma)

89
Q

What will a vestibular schwannoma do?

Causing?

A

Lesion CN 7 and bump Chorda Tympani

Loss of taste in ant. 2/3rds of tongue on IPSILATERAL side

Hearing loss (stapedius m. Paralyzed)

Impaired secretions of nasal, lacrimal, submand, and sublingual glands

90
Q

What results from damage to the Distal Geniculate Ganglion?

A

Taste may or may not be lost

Ipsilateral face paralysis

(First ganglion where facial nerve fibers carrying taste info synapses)