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Neuro Block 7 > Lecture 2: Olfaction and Taste > Flashcards

Lecture 2: Olfaction and Taste Flashcards

1
Q

The sensation of odors that results from the detection of odorous substances aerosolized in the environment

A

Olfaction

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2
Q

The sensation evoked by stimulation of taste receptors located in the oropharyngeal cavity

A

Taste (gustation)

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3
Q

How does the somatosensory system contribute to flavor?

A

Detecting irritating components in smells like ammonia or the “hot” in spicy foods like peppers, also thermal and texture perceptions through branches of the trigeminal nerve

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4
Q

Orexia

A

Appetite

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5
Q

Anorexia

A

LACK of appetite

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6
Q

Anosmia

A

Lack of smell

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7
Q

Are humans macrosmatic or microsmatic creatures?

A

Microsmatic - less dependent on smell than many other mammals

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8
Q

Through connections with _____ and _____ structures, the olfactory system plays a role in the pleasures associated with eating and with the many scents that make up our world

A

Cortical

Limbic

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9
Q

5 taste sensations

A

Salty, sweet, sour, bitter, umami

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10
Q

Umami is important for

A

identification of amino acids (tastes like MSG)

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11
Q

Taste, which originates from receptors in the oropharyngeal cavity, is important to determine ______. This information is relayed by neural pathways that underlie various ingestive and digestive functions

A

the acceptance or rejection of foods

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12
Q

Retronasal smell

A

Sensation of taste through smell, volatile odorants in food can travel through oropharyngeal cavity to reach the olfactory epithelium

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13
Q

What cells express products of the several hundred olfactory receptor cells?

A

Bipolar olfactory receptor neurons

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14
Q

A single odor molecule activates how many olfactory receptors?

A

Several hundred

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15
Q

Where is the olfactory bulb located?

A

Cribriform plate of the ethmoid bone, inferior to the medial aspects of the frontal bone

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16
Q

Olfactory structures are vulnerable to trauma of what areas?

A

Facial trauma, particularly of nasal bones, frontal bone, or concha of the nose

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17
Q

The receptors responsible for transduction of odor molecules are found where?

A

Olfactory mucosa

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18
Q

Where is the olfactory mucosa located?

A

Roof of the nasal cavity on the inferior surface of the cribriform plate and along the nasal septum and medial wall of the superior turbinate

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19
Q

Composition of olfactory mucosa

A

Superficial acellular layer of mucus that covers the olfactory epithelium and underlying lamina propria

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20
Q

How is the olfactory epithelium differentiated from respiratory epithelium?

A

Its faint yellowish color and greater thickness

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21
Q

Olfactory epithelium is pseudo stratified and contains what? (4)

A

Olfactory receptor neurons, supporting cells (sustentacular cells), basal cells (replacing receptor neurons), and the ducts of small glands (Bowman’s glands)

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22
Q

Bodies of bipolar olfactory neurons are found where?

A

Basal 2/3 of epithelium

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23
Q

Each bipolar olfactory neuron has a single thin apical dendrite and ______

A

A basally located unmyelinated axon

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24
Q

10-30 nonmotile cilia on the olfactory receptors arise and protrude into the overlying mucus layer. The apical dendrite of these cells extend to where?

A

Apical dendrite extends to the surface of the epithelium

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25
Q

Nonmotile cilia contain receptors for what?

A

Odorant molecules

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26
Q

Unmyelinated axons of an olfactory receptor neuron pass through the lamina proper and group together into bundles called ______ which collectively make ______

A

Olfactory fila

Olfactory nerve (CN 1)

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27
Q

Olfactory file pass through ______ to terminate in the olfactory bulb

A

Cribriform plate

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28
Q

Location and attachment of olfactory bulb

A

Forebrain structure located on the ventral surface of the frontal lobe in the olfactory sulcus and is attached to the rest of the brain by the olfactory tract

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29
Q

Olfactory perception begins when

A

Volatile odor molecules are inhaled and contact the mucus layer of the olfactory epithelium

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30
Q

Odorants, like hydrophobic odorant musk, cross the mucus by

A

Interacting with small proteins called odorant-binding proteins

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31
Q

After crossing the mucus, odor molecules bind to

A

Odorant receptors on the cilia of the olfactory receptor neurons

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32
Q

What are odorant receptors?

A

Membrane proteins, GPCRs

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33
Q

Humans have as many as ______ types of odorant receptors

A

1000

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34
Q

Binding of the ligand generates depolarization in the ______ (though the adenylyl cyclase pathway (IP3 pathway) of the olfactory receptor neuron

A

dendrite

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35
Q

Axons of olfactory receptor neurons communicate with

A

2nd order neurons of the olfactory tract (mitral cells)

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36
Q

Axons of mitral cells emerge

A

From the caudal portion of the olfactory bulb to form the lateral olfactory tract

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37
Q

Where do axons of mitral cells terminate?

A

Areas on the ventral surface of the frontal lobe, the olfactory cortex

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38
Q

The olfactory system is the only system that bypasses the ______

A

thalamus

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39
Q

Olfactory system projects directly to the

A

Cortex

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40
Q

Lateral olfactory tract sends collaterals to the

A

Subcortical limbic structures

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41
Q

Olfactory cortex also sends projections to ______, which is important for what?

A

Orbitofrontal cortex and insula either directly or via a relay in the thalamus
Discrimination and identification of odors

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42
Q

Lesions in the orbitofrontal cortex lead to

A

Loss of discrimination and identification of odors

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43
Q

Insular and orbitofrontal also receive what input

A

taste

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44
Q

Medial orbitofrontal cortex plays a role in

A

Integrating olfactory, taste, and other food-related cues that produce the experience of flavor

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45
Q

In addition to neocortical, the olfactory cortex also sends projections directly to

A

lateral hypothalamus and hippocampus

46
Q

Lateral hypothalamus projections important for

A

Feeding behavior

47
Q

Hippocampus projections important for

A

Centers concerned with learning and behavior

48
Q

Conductive olfactory deficits

A

Can be caused by nasal polyps, septal deviation, and inflammation

49
Q

Sensorineural olfactory deficits can be triggered by processes that damage

A

olfactory receptor neurons or parts of the olfactory CNS

50
Q

Head injuries result in what type of deficit and why?

A

Sensorineural, the olfactory fila may be torn loose from the olfactory bulb as a consequence of head trauma

51
Q

Neurodegenerative conditions result in what type of deficit?

A

Sensorineural

52
Q

Severe upper respiratory infections result in what type of deficit and why?

A

Sensorineural, due to permanent damage to olfactory receptor neurons

53
Q

Seizures originating in the ______ may begin with an illusion of smell or taste, most often an unpleasant one and can include motor phenomena such as chewing movements or smacking of the lips
These are called ______ seizures

A

Piriform cortex, in the vicinity of the uncus

Uncinate

54
Q

Loss of smell is often associated with

A

Polyps

55
Q

Causes of nasal polyps

A

Inflamed mucous membranes or allergic reactions and can obstruct the nasal cavities or extend into the nares

56
Q

Rhinitis or sinusitis

A

Block the access of odorants to the olfactory epithelium

57
Q

Head trauma deficits

A

Damage to the central olfactory pathways or olfactory receptor axons as they pass through the cribriform plate

58
Q

Fractures along the anterior base of the skull may cause

A

Drainage of CSF into the paranasal sinuses and through the nose (CSF rhinorrhea)

59
Q

Cocaine use

A

perforation of the nasal septum, but normal odor perception

60
Q

Specific anosmia

A

Autosomal recessive trait in which healthy individuals with otherwise normal olfactory acuity are unable to perceive the odor of a particular compound or class of compounds

61
Q

Olfactory hallucination occurs in what conditions

A

Schizophrenia and Korsakoff psychosis

62
Q

Chief complaint of patients with chemosensory disturbances

A

Loss or alteration of taste

63
Q

Detection of an odorous substance indicates the integrity of the

A

Peripheral nerve and its pathway

64
Q

Identification of odor reveals

A

Intact cortical function

65
Q

If the patient is aware of a smell but cannot recall the name of the scent

A

Disorder is likely to reside at higher levels of the sensory system

66
Q

Olfactory losses may be manifested _____ or _____

A

Unilaterally or bilaterally

67
Q

Unilateral deficiencies are typically observed subsequent to ______ or after ______

A

Nasal cavity disease

Tumor-associated compression of one olfactory bulb or tract

68
Q

Bilateral anosmia is usually sustained in response to

A

Head trauma or common cold

69
Q

Age related declines in olfaction are common or uncommon?

A

Common

70
Q

Does age related decline in olfaction occur gradually or suddenly?

A

Gradually

71
Q

Olfactory dysfunction is encountered in the early stages of what diseases?

A

Alzheimer’s, Parkinson’s, Huntington chorea

72
Q

The sense of taste results from an interaction between ______ and ______ located in sensory organs called taste buds

A

Gustatory stimuli

Receptor cells

73
Q

Taste buds are most obvious where? But are found where?

A

Tongue

Throughout the oral cavity

74
Q

Fungiform papillae

A

2-4 dorsally, anterior 2/3 of tongue

75
Q

Foliate papillae

A

2-9 clefts, taste buds in clefts, posterior margin of tongue

76
Q

Circumvallate papillae

A

8-12, taste buds in cleft

77
Q

Where are extra-lingual taste buds found

A 
Epithelia, NOT papillae 
Soft palate (junction of soft and hard palate), pharynx, epiglottis and aryepiglottal folds
78
Q

Why are there taste buds in the pharynx and epiglottis?

A

Detection of food and suppression of aspiration into trachea

79
Q

Type 1 taste bud cells

A

mainly perform supportive functions

80
Q

Type 2 taste bud cells

A

Receptor cells, posses G-protein coupled receptors for bitter, sweet, and umami compounds

81
Q

Type 3 taste bud cells

A

Type III: secrete neurotransmitters

82
Q

Type 4 taste bud cells

A

Basal cells, are progenitor cells

83
Q

Taste cells extend from

A

basal lamina to surface of epithelium

84
Q

Apical ends of taste cells are covered with

A

Microvilli of various lengths that extend into a taste pore

85
Q

The taste pore forms a pocket to

A

Permit contact between the microvilli of the taste cell and the external milieu

86
Q

Taste pore is filled with

A

Protein rich substance though which substances must pass to reach the taste cell microvilli

87
Q

Life span of taste cell

A

10-14 days

88
Q

New taste cells arise from

A

Basal cells

89
Q

In response to taste stimulation, receptor cells secrete

A

ATP

90
Q

ATP does what in taste?

A

Excited adjacent type 3 cells, which form synapses with the afferent fibers of the sensory neuron

91
Q

Afferent taste fibers penetrate the basement membrane and form

A

Sensory nerve fibers

92
Q

Taste transduction is initiated when

A

soluble chemicals diffuse through taste pore and interact with receptors located on the apical microvilli of the taste cells

93
Q

Interaction between ligand and receptor of the taste cells causes

A

Increase in intracellular calcium, either by release of calcium from internal stores or activation of voltage-gated calcium channels

94
Q

Calcium release in the taste transduction pathway results in

A

A release of chemical transmitters (serotonin) at the afferent synapse, which leads to AP in afferent fiber

95
Q

Facial nerve (CN 7)

A

Chorda tympani = anterior 2/3 of tongue

Greater superficial petrosal nerve innervates soft palate

96
Q

Glossopharyngeal nerve (CN IX)

A

Posterior 1/3 of tongue

97
Q

Vagus nerve (CN X)

A

Small area around the epiglottis

98
Q

General sensation detecting (hot, etc.) is carried through what nerve?

A

Trigeminal (CN V)

99
Q

TASTE PATHWAY

A

The cell bodies of facial nerve fibers serving taste are located in the geniculate ganglion, and their central processes enter the brainstem at the pontomedullary junction in the intermediate nerve, which is actually a part of the facial nerve.
These primary afferent taste fibers enter the solitary tract and synapse on cells of the rostral solitary nucleus.
Taste fibers in cranial nerves IX and X have their cell bodies of origin in the inferior ganglia (petrosal and nodose, respectively) of these cranial nerves.
The central processes of these fibers, enter the medulla, travel in the solitary tract, and terminate on neurons in the adjacent solitary nucleus.

100
Q

Is taste ipsilateral or contralateral?

A

Ipsilateral

101
Q

Principal visceral afferent nucleus of the brainstem is

A

Solitary nucleus

102
Q

Divisions of solitary nucleus

A

Rostral (gustatory) and caudal (visceral or cardiorespiratory)

103
Q

What terminates in rostral SN

A

Taste fibers traveling in CN VII, IX, and X

104
Q

Axons arising from 2nd order taste neurons in the gustatory nucleus ascend in the ipsilateral central tegmental tract and terminate in the

A

VPM (ventral posteromedial nucleus) of the thalamus

105
Q

Axons from the VPM travel through the ipsilateral posterior limb of the internal capsule to terminate in

A

The inner portion of the anterior insular cortex and on the lateral frontal operculum convexity of the post central gyrus

106
Q

What pathway is responsible for discriminative aspects of taste and is exclusively ipsilateral?

A

Solitary nucleus -> VPM -> cortex

107
Q

Sensation we perceive when eating and drinking is the combination of what 3 different kinds of input?

A

Direct chemical stimulation of taste buds, Stimulation of olfactory receptors by vapors from food, and stimulation of chemical-sensitive and somatosensory free nerve endings of the trigeminal and other nerves in the mucous membranes of the oral and nasal cavities

108
Q

Ageusia

A

Loss of taste sense (rare, would require injury to tongue or CN VII, IX, or X afferent fibers)

109
Q

Hypoguesia

A

Decreased taste sensitivity

110
Q

Paraguesia/dysguesia

A

Distortions in taste perceptions

111
Q

Clinical scenarios for decreased taste perception/sensitivity

A

Radiation/chemotherapy, head/brain trauma, surgical injury, or medications

Neuro Block 7 (8 decks)

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