Gustatory and Olfactory Receptors and Pathways Flashcards
What are the three types of papillae which contain taste buds? The one that is used for friction?
- Fungiform - mushroom shaped ~4 buds
- Vallate - moat-shaped
- Foliate - folds on side of tongue
Friction - filiform
What are the four cell types of the taste bud and what do they do?
- Parietal cells - give rise to sustentacular + basal cells
- Basal cells - give rise to gustatory cells
- Gustatory cells - chemoreceptor cells on apical membrane
- Sustentacular cells - supporting cells
Why do old people lose their sense of taste?
Lose taste buds throughout life at a rate of 1% per year
What types of synapses do nerve fibers make with gustatory cells?
Chemical synapses
What type of receptor does each taste sense use?
Sweet - GPCR Sour - ionic Salty - ionic Bitter - GPCR Umami - GPCR
What nerve innervates the taste buds on the epiglottis?
CNX
What are the relevant ganglia for taste perception? Where do their roots enter?
Anterior 2/3 - Geniculate ganglion of 7 - cerebellopontine angle
Posterior 1/3 - Petrosal ganglion of 9 - postolivary sulcus, rostral medulla
Epiglottis - Nodose ganglion of 10 - postolivary sulcus, mid medulla
What is the gustatory nucleus?
Rostral 1/2 of solitary nucleus, where 7, 9, 10 central processes synapse for taste.
What are the reflex pathways for gustation?
Rostral solitary nucleus gives second order taste fibers which synapse bilaterally to inferior salivatory nucleus and superior salivatory nucleus.
What is the superior salivatory nucleus?
Nucleus which controls salivation for submandibular, sublingual, and lacrimal glands
What is the inferior salivatory nucleus?
Nucleus receiving bilateral contributions for salivation from the parotid gland
What is the course of the second order neurons of the taste pathway?
Ascend from the rostral solitary nucleus through the central tegmental tract to the most medial part of the VPM thalamus, where they synapse on tertiary taste neurons
What is the course of the third order neurons of the taste pathway?
Axons from VPM thalamus go through internal capsule + corona radiata. There are two primary cortical taste centers.
- Parietal operculum - ventral aspect of postcentral gyrus
- Anterior portion of insular cortex
Where does crude awareness of taste vs fine discrimination occur?
Crude awareness = thalamus
Discrimination = cortical levels
What is the general function of the insular cortex for olfaction and taste?
It is the place where both oolfactory and taste sensation are integrated
What is the word for distorted sense of taste?
Dysgeusia
What is the primary olfactory neuron called and where is it located?
The olfactory bipolar neuron. Located in the superior nasal concha and adjacent nasal septum.
What is the turnover rate of gustatory cells and olfactory bipolar neurons? Where do they come from?
Gustatory - 7-10 days
Olfactory bipolar - 30-60 days
They are derived from basal cells
Where do the bipolar neurons processes go?
Dendrites - to apical epithelial surface, forming dendritic bulb
Axons - joins the olfactory nerves
What does the dendritic bulb do?
Has ciliary projections which project into the covering film of watery mucus
What is the receptor type of olfaction and how do we detect such a wide range of smells?
There are over 1000 different receptor types, and each cell only expresses one, so there is a wide diversity.
Receptor type = G-protein coupled receptor.
What is an olfactory filum? Where do they terminate?
A collection of 10-100 unmyelinated axons of olfactory bipolar neurons which are organized by Schwann cells. They project through the cribriform plate of ethmoid bone and terminate in olfactory bulb.
What is the olfactory tract vs olfactory nerve?
Nerve - prior to reaching olfactory bulb, the collection of all olfactory fila
Tract- collection of axons from the olfactory bulb (second order olfaction neurons)
What is the neuron type of the olfactory bulb?
Mitral cell - receives input at glomeruli from olfactory bipolar neurons at apical dendrites
