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Neuro Exam 3 > Neuroanatomy of Taste and Olfaction > Flashcards

Neuroanatomy of Taste and Olfaction Flashcards

1
Q

What are the 4 basic tastes?

A

Sweet
Sour
Salty
Bitter

Plus umami

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2
Q

Where is the olfactory bulb located?

A

Cribiform plate of ethmoid bone

Inferior to medial aspects of frontal lobe

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3
Q

Receptors for transduction of odor molecules are where?

A

Olfactory mucosa
Roof of nasal cavity on inferior surface of cribrifrom plate
Along nasal septum and medial wall of superior turbinate

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4
Q

Describe olfactory receptor cells.

A

Single dendritic process
Specialized non-motile cilia w/ odorant receptors
Odorant receptors = GPCRs
Ligand binding sends signal to olfactory bulb

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5
Q

What are basal cells?

A

Stem cells for olfactory receptor and supporting cells

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6
Q

What are brush cells?

A

Ciliated, columnar epithelial cells

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7
Q

What are supporting/sustentacular cells?

A

Provide mechanical and metabolic support to olfactory receptor cells

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8
Q

What are olfactory fila?

A

Multiple nerve fibers that make up the olfactory nerve

Pass through cribriform plate and terminate in olfactory bulb

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9
Q

How does olfactory perception occur?

A

Odor molecules are inhaled and contact mucus layer covering the epithelium

Aqueous solution of proteins, electrolytes, and odorant-binding proteins –> receptors –> transduction

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10
Q

Describe what happens when a ligand binds to the odorant receptor.

A

Activation of 2nd messenger pathway –> adenyl cyclase –> cAMP –> cation channels open –> depolarization

Sufficiently large depolarization initiates AP to olfactory bulb

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11
Q

The olfactory bulb is made of how many layers? What are they?

A 
5 layers:
Olfactory Nerve layer 
Glomerular layer 
External Plexiform layer 
Mitral Cell layer 
Granule Cell layer
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12
Q

What does the olfactory nerve layer contain?

A

Axons of ORNs (olfactory receptor neurons)

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13
Q

What does the glomerular layer contain?

A

ORNs synapsing on dendrites of mitral and tufted cells –> efferent output of bulb

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14
Q

What does the external plexiform layer contain?

A

Dendrites of tufted, mitral, and granule cells
Cross talk with granule cells
Moodulates tufted and mitral cell output

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15
Q

What does the mitral cell layer contain?

A

Mitral cells and axons of tufted/granule cells

Centrifugal fibers traverse this layer

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16
Q

What does the granule cell layer contain?

A

Granule cells = principle interneuron of olfactory bulb

Output = dendrodendritic GABA (decreased activity of mitral and tufted cells)

Layer contains axons of mitral and tufted cells and centrifugal afferents

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17
Q

What runs through the olfactory tract?

A

Fibers of lateral olfactory tract

Cells of anterior olfactory nucleus

Fibers of anterior limb of anterior commissure

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18
Q

What is significant about the anterior commissure?

A

It’s how many centrifugal fibers reach olfactory bulb.

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19
Q

What are periglomerular cells?

A

Interneurons of the glomarular level, branch extensively

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20
Q

What do centrifugal afferents do?

A

They send input from other central nervous systems to the glomerular layer.

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21
Q

What makes up the lateral Olfactory tract?

A

Axons of mitral and tufted cells emerginign from caudal Olfactory bulb

22
Q

Where does the lateral Olfactory tract terminate?

A

Olfactory cortex

On ventral surface of telencephalon

23
Q

What structures make up the olfactory cortex?

A

Anterior Olfactory nucleus

Olfactory tubercle

Piriform cortex

Anterior cortical amygdaloid nucleus

Periamygdaloid cortex

Lateral entorhinal cortex

24
Q

Where does the lateral Olfactory tract send collaterals?

A

Anterior Olfactory nucleus

Other areas of olfactory cortex

Subcortical limbic structures

25
Q

What are the major targets of the anterior olfactory nucleus?

A

B/L olfactory bulbs

Contralateral anterior olfactory nucleus

26
Q

What is a hallmark of the olfactory bulb?

A

It project directly to cortex and does not relay via thalamus.

27
Q

To where does the olfactory cortex project its fibers?

A

Lateral hypothalamus

Dorsomedial thalamic nucleus

Insular and orbital cortex

Olfactory bulb

28
Q

To we here else does the lateral entorhinal cortex project its fibers?

A

Hippocampus

29
Q

Why is neocortical representation of olfaction important?

A

For discrimination and identification of odors

30
Q

What is significant about the orbitofrontal cortex in regards to olfaction?

A

It integrates olfactory, taste, and other food-related cues that produce experience of flavors.

31
Q

What is the lateral hypothalamus responsible for in regards to olfaction?

A

Gets input from the piriform cortex and anterior olfactory nucleus —> important for feeding behavior

32
Q

Why is hippocampal input important for olfaction?

A

Links Olfactory input to learning and behavior

33
Q

Define Anosmia.

A

Loss of smell

34
Q

Describe hyposmia or olfactory hypesthesia.

A

Decreased sensitivity to odorants

Can be associated with nasal polyps, non cancerous growths that occur in nasal cavity or within sinuses

35
Q

How is tast transduction initiated?

A

Soluble chemicals diffuse through contents of taste pore and bind to receptors on apical microvilli of taste cells

36
Q

What happens after taste transduction is initiated?

A

Interaction of stimulus with receptor can result in depolarization or hyperpolarization

Sufficient depol —> AP in taste cell —> afferent fibers of first order taste neurons

37
Q

What does the chorda tympani innervate?

A

Innervates fungiform papillae on anterior 2/3 of tongue and anterior foliage papillae

38
Q

What does the greater petrosal nerve innervate?

A

Innervates taste buds on soft palate

39
Q

Where are the cell bodies for CN 7 located?

A

Geniculate ganglion

40
Q

Walk through the tract of CN 7.

A

Enters brainstem at pontomedullary junction via intermediate nerve —> solitary tract —> target cells of solitary nucleus —> gustatory nucleus (rostral portion)

41
Q

What is the glossopharyngeal n significant for in regards to taste?

A

Lingual-tronsilar branch innervates taste buds in Vallate papillae and posterior foliate papillae

42
Q

What is the vagus n significant for in regards to taste?

A

Superior laryngeal n innervates taste buds of epiglottis and esophagus.

43
Q

Where are the cell bodies of the taste fibers in CN 9 & 10? Ultimate target?

A

Inferior ganglia:
Petrosal = CN 9
Nodose = CN 10

Ultimate target = gustatory nucleus (rostral portion)

44
Q

Describe the central taste pathway.

A

Pathway is ipsilateral

2nd order neurons travel via ipsilateral central tegmental tract —> ventral posteromedial nucleus —> posterior limb of internal capsule —> inner portion of frontal operculum and anterior insular cortex

End = Brodmann 3b (postcentral gyrus)

45
Q

Why is the central taste pathway significant?

A

Responsible for discriminative aspect of taste

46
Q

What happens with a lesion at CN 7 root or in internal auditory meatus (vestibular schwannoma)?

A

Loss of taste perception from ipsilateral anterior 2/3 of tongue

Paralysis of ipsilateral facial muscles

Hype racists = paralysis of stapedius m.

Impaired secretion of nasal, lacrimal, submandibular, and sublingual glands

47
Q

What happens when there is damage to the geniculate ganglion?

A

May or may not result in taste loss depending on origin of chorda tympani

Ipsilateral facial paralysis

48
Q

Describe ageusia.

A

Complete loss of taste, rare

49
Q

Describe hypogeusia.

A

Decreased taste sensitivity

50
Q

Describe parageusia.

A

Distortions in perception of taste

Causes: drug use or meds

Neuro Exam 3 (8 decks)

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