Lecture 23: Chemical senses Flashcards

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1
Q

Olfactory epithelium are actually…Where do these cells project?

A

The olfactory nerve cells; sends rootlets (axons) through the cribiform plate to the olfactory bulb

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2
Q

Where is the first synapse in the olfactory system?

A

Between the olfactory bulb and the axons of the olfactory epithelium

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3
Q

The olfactory bulb is considered part of the…

A

CNS

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4
Q

What does the olfactory system lack?

A

Thalamic relay

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5
Q

Where does the olfactory tract travel to?

A

Directly into olfactory cortex (piriform cortex: uncus, amygdala, parahippocampal gyrus)

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6
Q

Where does the olfactory cortex project?

A

Orbitofrontal cortex, thalamus, hypothalamus; entorhinal –> hippocampus

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7
Q

About half of the nasal cavity is what? What’s the other half?

A

Respiratory and olfactory epithelium

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8
Q

Odorants bind to…this gets turned into?

A

Receptors on olfactory epithelium cilia –> AP

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9
Q

What is a basal cell?

A

Stem cells to make new olfactory receptor neurons

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10
Q

In olfactory epithelium, you find…(4)

A

Receptor cells, basal cells, supporting cells, Bowman’s glands (make protective mucus)

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11
Q

Olfactory receptors and odor discrimination

A

In general, individual olfactory neurons express only one type of odorant receptor and specific subtypes of odorant receptors preferentially distribute within one of four bilaterally symmetric zones of the olfactory epithelium

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12
Q

Olfactory nerve is mostly ipsi/contralateral

A

Ipsilateral

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13
Q

First layer of olfactory bulb contains the (what happens here?)…What’s the name of the second cell? What’s it’s function?

A

Glomerulus (first synapse); mitral cells; principal projection neurons

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14
Q

T/F: There is top-down processing in olfactory bulb. What type of cell?

A

True! Suppresses background smells; granule cell

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15
Q

What things do olfactory cortex projections do? (3)

A

Hippocampus: Olfactory-guided memory; Hypothalamus: feeding behavior, ANS responses; Cortex: discrimination/identification of odors

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16
Q

Unique attributes of olfactory system (4)

A
  1. Somas of parimry afferent neurons occupy surface epithelium; 2. Axons enter cortex directly; 3. Primary afferent neurons undergo continuous turnover; 4. Pathway to cortical centers is ipsilateral
17
Q

What are two physical responses to odorants?

A
  1. Visceral motor responses to food; 2. Reproductive/endocrine functions (menstrual cycles, mother-child interactions, pheromones)
18
Q

Olfactory agnosia

A

Aware of smell but not of name

19
Q

Cacosmia

A

Formation of repugnant/disagreeable olfactory auras

20
Q

Parosmia/Dysosmia

A

Distortion in a smell

21
Q

Causes of anosmia, hyposmia

A

URI (mucus blocks access of odorants), trauma (cribiform plate: ethmoid bone, look for Raccoon Eyes or CSF Rhinorrhea), tumors (neuroblastomas, meningiomas), aging (normal)/neurodegenerative (early clue to Alzheimer’s, Parkinson’s), toxins/medications/drugs/smoking

22
Q

Causes of hallucinations, cacosmia, parosmia

A

Epilepsy, psychiatric disorder

23
Q

Causes of hyperosmia

A

Migraine, psychosis, substance use

24
Q

Where does taste information go from solitary nucleus? Where from here?

A

VPM of thalamus –> insula (gustatory cortex) and frontal cortex (interprets what you’re eating)

25
Q

Solitary nucleus also projects to…

A

Hypothalamus (regulation of eating), amygdala (emotional response to food)

26
Q

Taste _____ are located within taste ________

A

Buds; papillae

27
Q

How are taste buds replaced?

A

Basal cells

28
Q

What is a common misconception of the tongue taste system?

A

All tastes can be detected over the entire surface of the tongue but regions have varying thresholds for each taste

29
Q

How do we distinguish types of taste?

A

Each tastant category corresponds to a distinct class of receptor molecules expressed in subsets of taste cells which are also maintained in the representation of taste information in the CNS

30
Q

Transduction of taste information starts where on the taste bud? Then what? First synapse?

A

Apical domain; electrical signals are generated at basal domain via graded receptor potentials and NT release; synapses on primary afferent axons of CNs

31
Q

Primary gustatory cortex includes which two brain regions…(2)

A

Anterior insula and frontal operculum

32
Q

Ageusia

A

Complete loss of taste (rare)

33
Q

Hypogeusia

A

Decreased taste (normal aging)

34
Q

Parageusia/dysgeusia

A

Unpleasant perception of taste when it normally taste good (common after chemotherapy or in elderly)

35
Q

Cacogeusia

A

Perception of an unpleasant taste (often seizure in insula/operculum)

36
Q

Gustatory hallucinations

A

Tasting when no taste present (migraines, seizures, psychiatric: though rare)

37
Q

A tumor where could cause taste disturbance? These often lead to taste loss on one/both sides?

A

Internal auditory meatus (compressing CN VII), oropharyngeal tumors; ipsilateral tumor

38
Q

Some other causes of taste problems (4)

A

Bell’s palsy, head trauma, radiation therapy, diabetes