Lecture 36 - Chemical senses Flashcards by Raegan Chambers

Where is the olfactory mucosa?

Roof of the nasal cavity

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What two things does flavor perception drive?

Olfactory, taste, and somatosensory cues

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What is within the olfactory mucosa?

Mucus layer with odorant-binding proteins, olfactory, epithelium, underlying basal lamina (Bowman’s gland)

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What is mucus secreted from in the olfactory mucosa?

Supporting cells
– and –
Bowman’s gland

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What cell types are within the olfactory epithelium?

Olfactory receptor neurons
Supporting/sustentacular cells
Basal cells

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What is the function of the basal cells in the olfactory epithelium?

Stem cells; give rise to new receptors

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What is the lifespan of the olfactory receptors?

30-60 days

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What is the function of the supporting cells in the olfactory epithelium?

Columnar cells - contribute to mucus production

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What kind of neuron are the olfactory receptor neurons?

Bipolar neurons

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What are the two regions of the olfactory bipolar neurons?

Apical dendrite
– and –
basal unmyelinated axon

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What is occurring at the dendritic end of the olfactory neurons?

Terminates in the olfactory vesicle

Protrude into the mucous layer and contain receptors

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What happens at the basal end of the olfactory receptors?

Projects through the Cribriform plate with other axons as bundles (Olfactory fila)

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What does the basal end of the olfactory receptor neurons synapse on?

Glomeruli of the olfactory bulb

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How do the odorants in the air reach the olfactory receptor?

Cross the mucosa via binding to odorant binding proteins

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How many odorant receptors does each olfactory receptor get?

One

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What are the two transduction mechanisms that occur in olfactory transduction?

One cation
– and –
One calcium

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What happens to the olfactory neuron when transduction occurs?

Depolarization

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What is receptor cycling?

Once odorant receptor becomes saturated it retreats into the cell

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What type of receptor is a olfactory receptor?

G-protein coupled

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What type of system is the olfactory system? (in regards to how it works)

Change detector system - detects new odorants and ignores old ones

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What is the central olfactory pathway? (basic)

Olfactory bulb - Tract - Cortex

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How many layers are within the olfactory bulb?

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What happens with the axons of the olfactory receptor?

Pass through the cribriform plate

Terminate in the olfactory bulb

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What are the five layers of the olfactory bulb?

Olfactory nerve 
Glomerular 
External plexiform 
Mitral cell 
Granule cell

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What is within the olfactory nerve layer?

AXONS of the olfactory receptor neurons

What is within the glomerular layer?

Synapses of olfactory receptor neurons on mitral and tufted cells Periglomerular cells Tonography of odors

What types of neurons are periglomerular cells?

Interneurons

How are glomerular synapses organized?

Each synapse receives same odorant information

What synapses on the glomeruli after the olfactory receptors?

Mitral cells

What is contained within the external plexiform layer?

Cell bodies of tufted cells

What is contained within the mitral layer?

Cell bodies of mitral cells

What are the three cell layers of the olfactory cortex?

Periamygdaloid - Piriform - Enorhinal

What is the path of olfactory information through the olfactory cortex?

``` anterior olfactory nucleus olfactory tubercle piriform cortex amygdala periamygdaloid cortex entorhinal cortex ```

What is the main output for the association fiber system?

Lateral hypothalamus

What are other, besides lateral hippocampus, regions that the association fiber system projects to?

Ipsilateral olfactory bulb Contralateral olfactory bulb/cortex Hippocampus

What projects to the hipocampus?

Lateral entorhinal cortex

What does the anterior olfactory nucleus project to?

Ipislateral/Contralateral olfactory bulb

What is important for feeding behavior?

Olfactory cortex projecting to the lateral hypothalamus

What is important for learning behavior?

Entorhinal cortex neurons projecting to the hippocampus

What is responsible for odor discrimination and identification?

Orbitofrontal cortex and insula

What also goes to the Orbitofrontal and insula?

Taste input

What is disosmia?

Reduction/loss of sense of smell

What are three things that can cause disosmia?

Mucosal Obstruction Nerve/brain

What is the function of the vomeronasal organ?

Sexual activity - Flehman reaction - Emotional states - Illnesses

What are the three types of papillae on the tongue?

Vallate - Foliate - Fungiform

What part of the tongue do fungiform papillae cover?

Anterior 2/3

What part of the tongue does the vallate papillae cover?

8-12 in V-shape on posterior tongue

Where are the foliate papillae?

one on each side of lateral tongue

What are the characteristics of a supertaster?

Higher density of fungiform papillae Experience greater oral burn and oral touch Supersniffers as well

Where are taste buds located?

Tongue papillae

What is the structure of a taste bud?

Taste pore - opening | Innervated by afferent neurons

What is the lifespan of a taste bud?

10-14 days

What part of the taste bud does the supporting cell make/

The outside portion

How many taste receptors to a taste bud?

40-60

What is the apical end of the taste bud covered in?

Microvilli

How does salty transduction occur?

Sodium of salt taste molecules may eneter through cation channels

What does sour transduction occur?

Protons of the sour taste molecules may block potassium channels

How is sweet, bitter, and sour tasted?

G protein coupled receptors

What is the central taste pathway for the anterior 2/3 of the tongue?

Fungiform/Foliate papillae - taste afferents - chorda tympani of facial nerve - geniculate ganglion - ipsilateral rostral solitary nucleus

What is the central taste pathway of the posterior 1/3 of the tongue?

Vallate papillae/Foliate papillae - taste afferent neurons - glossopharyngeal n. - Inferior ganglion of CN IX - ipsilateral rostral solitary tract

What is the central pathway for the soft palate?

Extralingual taste buds - taste afferent neurons - greater petrosal branch of the Facial N. - Geniculate ganglion - Ipsilateral rostral solitary nucleus

What is the central taste pathway for the epiglottis/esophagus?

Extralingual taste buds - taste afferent neurons - superior laryngeal br. of vagus n. - inferior ganglion of CN X - ipsilateral rostral solitary nucleus

What are the three ganglia involved with taste?

Geniculate - Petrosal - Nodose

What CN is the geniculate n. related to?

Facial n.

What CN is the petrosal ganglia related to?

CN IX - Glossopharyngeal

What CN is the nodose ganglia related to?

Vagus n.