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

Lecture 2: Olfaction and Taste Flashcards

(111 cards)

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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
Nonmotile cilia contain receptors for what?
Odorant molecules
26
Unmyelinated axons of an olfactory receptor neuron pass through the lamina proper and group together into bundles called ______ which collectively make ______
Olfactory fila Olfactory nerve (CN 1)
27
Olfactory file pass through ______ to terminate in the olfactory bulb
Cribriform plate
28
Location and attachment of olfactory bulb
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
29
Olfactory perception begins when
Volatile odor molecules are inhaled and contact the mucus layer of the olfactory epithelium
30
Odorants, like hydrophobic odorant musk, cross the mucus by
Interacting with small proteins called odorant-binding proteins
31
After crossing the mucus, odor molecules bind to
Odorant receptors on the cilia of the olfactory receptor neurons
32
What are odorant receptors?
Membrane proteins, GPCRs
33
Humans have as many as ______ types of odorant receptors
1000
34
Binding of the ligand generates depolarization in the ______ (though the adenylyl cyclase pathway (IP3 pathway) of the olfactory receptor neuron
dendrite
35
Axons of olfactory receptor neurons communicate with
2nd order neurons of the olfactory tract (mitral cells)
36
Axons of mitral cells emerge
From the caudal portion of the olfactory bulb to form the lateral olfactory tract
37
Where do axons of mitral cells terminate?
Areas on the ventral surface of the frontal lobe, the olfactory cortex
38
The olfactory system is the only system that bypasses the ______
thalamus
39
Olfactory system projects directly to the
Cortex
40
Lateral olfactory tract sends collaterals to the
Subcortical limbic structures
41
Olfactory cortex also sends projections to ______, which is important for what?
Orbitofrontal cortex and insula either directly or via a relay in the thalamus Discrimination and identification of odors
42
Lesions in the orbitofrontal cortex lead to
Loss of discrimination and identification of odors
43
Insular and orbitofrontal also receive what input
taste
44
Medial orbitofrontal cortex plays a role in
Integrating olfactory, taste, and other food-related cues that produce the experience of flavor
45
In addition to neocortical, the olfactory cortex also sends projections directly to
lateral hypothalamus and hippocampus
46
Lateral hypothalamus projections important for
Feeding behavior
47
Hippocampus projections important for
Centers concerned with learning and behavior
48
Conductive olfactory deficits
Can be caused by nasal polyps, septal deviation, and inflammation
49
Sensorineural olfactory deficits can be triggered by processes that damage
olfactory receptor neurons or parts of the olfactory CNS
50
Head injuries result in what type of deficit and why?
Sensorineural, the olfactory fila may be torn loose from the olfactory bulb as a consequence of head trauma
51
Neurodegenerative conditions result in what type of deficit?
Sensorineural
52
Severe upper respiratory infections result in what type of deficit and why?
Sensorineural, due to permanent damage to olfactory receptor neurons
53
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
Piriform cortex, in the vicinity of the uncus | Uncinate
54
Loss of smell is often associated with
Polyps
55
Causes of nasal polyps
Inflamed mucous membranes or allergic reactions and can obstruct the nasal cavities or extend into the nares
56
Rhinitis or sinusitis
Block the access of odorants to the olfactory epithelium
57
Head trauma deficits
Damage to the central olfactory pathways or olfactory receptor axons as they pass through the cribriform plate
58
Fractures along the anterior base of the skull may cause
Drainage of CSF into the paranasal sinuses and through the nose (CSF rhinorrhea)
59
Cocaine use
perforation of the nasal septum, but normal odor perception
60
Specific anosmia
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
Olfactory hallucination occurs in what conditions
Schizophrenia and Korsakoff psychosis
62
Chief complaint of patients with chemosensory disturbances
Loss or alteration of taste
63
Detection of an odorous substance indicates the integrity of the
Peripheral nerve and its pathway
64
Identification of odor reveals
Intact cortical function
65
If the patient is aware of a smell but cannot recall the name of the scent
Disorder is likely to reside at higher levels of the sensory system
66
Olfactory losses may be manifested _____ or _____
Unilaterally or bilaterally
67
Unilateral deficiencies are typically observed subsequent to ______ or after ______
Nasal cavity disease | Tumor-associated compression of one olfactory bulb or tract
68
Bilateral anosmia is usually sustained in response to
Head trauma or common cold
69
Age related declines in olfaction are common or uncommon?
Common
70
Does age related decline in olfaction occur gradually or suddenly?
Gradually
71
Olfactory dysfunction is encountered in the early stages of what diseases?
Alzheimer's, Parkinson's, Huntington chorea
72
The sense of taste results from an interaction between ______ and ______ located in sensory organs called taste buds
Gustatory stimuli | Receptor cells
73
Taste buds are most obvious where? But are found where?
Tongue | Throughout the oral cavity
74
Fungiform papillae
2-4 dorsally, anterior 2/3 of tongue
75
Foliate papillae
2-9 clefts, taste buds in clefts, posterior margin of tongue
76
Circumvallate papillae
8-12, taste buds in cleft
77
Where are extra-lingual taste buds found
``` Epithelia, NOT papillae Soft palate (junction of soft and hard palate), pharynx, epiglottis and aryepiglottal folds ```
78
Why are there taste buds in the pharynx and epiglottis?
Detection of food and suppression of aspiration into trachea
79
Type 1 taste bud cells
mainly perform supportive functions
80
Type 2 taste bud cells
Receptor cells, posses G-protein coupled receptors for bitter, sweet, and umami compounds
81
Type 3 taste bud cells
Type III: secrete neurotransmitters
82
Type 4 taste bud cells
Basal cells, are progenitor cells
83
Taste cells extend from
basal lamina to surface of epithelium
84
Apical ends of taste cells are covered with
Microvilli of various lengths that extend into a taste pore
85
The taste pore forms a pocket to
Permit contact between the microvilli of the taste cell and the external milieu
86
Taste pore is filled with
Protein rich substance though which substances must pass to reach the taste cell microvilli
87
Life span of taste cell
10-14 days
88
New taste cells arise from
Basal cells
89
In response to taste stimulation, receptor cells secrete
ATP
90
ATP does what in taste?
Excited adjacent type 3 cells, which form synapses with the afferent fibers of the sensory neuron
91
Afferent taste fibers penetrate the basement membrane and form
Sensory nerve fibers
92
Taste transduction is initiated when
soluble chemicals diffuse through taste pore and interact with receptors located on the apical microvilli of the taste cells
93
Interaction between ligand and receptor of the taste cells causes
Increase in intracellular calcium, either by release of calcium from internal stores or activation of voltage-gated calcium channels
94
Calcium release in the taste transduction pathway results in
A release of chemical transmitters (serotonin) at the afferent synapse, which leads to AP in afferent fiber
95
Facial nerve (CN 7)
Chorda tympani = anterior 2/3 of tongue | Greater superficial petrosal nerve innervates soft palate
96
Glossopharyngeal nerve (CN IX)
Posterior 1/3 of tongue
97
Vagus nerve (CN X)
Small area around the epiglottis
98
General sensation detecting (hot, etc.) is carried through what nerve?
Trigeminal (CN V)
99
TASTE PATHWAY
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
Is taste ipsilateral or contralateral?
Ipsilateral
101
Principal visceral afferent nucleus of the brainstem is
Solitary nucleus
102
Divisions of solitary nucleus
Rostral (gustatory) and caudal (visceral or cardiorespiratory)
103
What terminates in rostral SN
Taste fibers traveling in CN VII, IX, and X
104
Axons arising from 2nd order taste neurons in the gustatory nucleus ascend in the ipsilateral central tegmental tract and terminate in the
VPM (ventral posteromedial nucleus) of the thalamus
105
Axons from the VPM travel through the ipsilateral posterior limb of the internal capsule to terminate in
The inner portion of the anterior insular cortex and on the lateral frontal operculum convexity of the post central gyrus
106
What pathway is responsible for discriminative aspects of taste and is exclusively ipsilateral?
Solitary nucleus -> VPM -> cortex
107
Sensation we perceive when eating and drinking is the combination of what 3 different kinds of input?
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
Ageusia
Loss of taste sense (rare, would require injury to tongue or CN VII, IX, or X afferent fibers)
109
Hypoguesia
Decreased taste sensitivity
110
Paraguesia/dysguesia
Distortions in taste perceptions
111
Clinical scenarios for decreased taste perception/sensitivity
Radiation/chemotherapy, head/brain trauma, surgical injury, or medications

Neuro Block 7 (8 decks)

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