Lecture 23: Chemical senses Flashcards Preview

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Flashcards in Lecture 23: Chemical senses Deck (38):
1

Olfactory epithelium are actually...Where do these cells project?

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

2

Where is the first synapse in the olfactory system?

Between the olfactory bulb and the axons of the olfactory epithelium

3

The olfactory bulb is considered part of the...

CNS

4

What does the olfactory system lack?

Thalamic relay

5

Where does the olfactory tract travel to?

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

6

Where does the olfactory cortex project?

Orbitofrontal cortex, thalamus, hypothalamus; entorhinal --> hippocampus

7

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

Respiratory and olfactory epithelium

8

Odorants bind to...this gets turned into?

Receptors on olfactory epithelium cilia --> AP

9

What is a basal cell?

Stem cells to make new olfactory receptor neurons

10

In olfactory epithelium, you find...(4)

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

11

Olfactory receptors and odor discrimination

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

12

Olfactory nerve is mostly ipsi/contralateral

Ipsilateral

13

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

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

14

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

True! Suppresses background smells; granule cell

15

What things do olfactory cortex projections do? (3)

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

16

Unique attributes of olfactory system (4)

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

What are two physical responses to odorants?

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

18

Olfactory agnosia

Aware of smell but not of name

19

Cacosmia

Formation of repugnant/disagreeable olfactory auras

20

Parosmia/Dysosmia

Distortion in a smell

21

Causes of anosmia, hyposmia

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

Causes of hallucinations, cacosmia, parosmia

Epilepsy, psychiatric disorder

23

Causes of hyperosmia

Migraine, psychosis, substance use

24

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

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

25

Solitary nucleus also projects to...

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

26

Taste _____ are located within taste ________

Buds; papillae

27

How are taste buds replaced?

Basal cells

28

What is a common misconception of the tongue taste system?

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

29

How do we distinguish types of taste?

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

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

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

31

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

Anterior insula and frontal operculum

32

Ageusia

Complete loss of taste (rare)

33

Hypogeusia

Decreased taste (normal aging)

34

Parageusia/dysgeusia

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

35

Cacogeusia

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

36

Gustatory hallucinations

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

37

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

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

38

Some other causes of taste problems (4)

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

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