DSA 1: Neuroanatomy of Gustation and Olfaction Flashcards
What are the four basic tastes?
Sweet
Salty
Sour
Bitter
How do we recognize many different tastes other than the basics?
Few taste receptors in different combinations result in different taste sensations.
Where are olfactory bulbs found?
Cribiform plate of ethmoid bone
What does the olfactory tract do?
Transmit sensory information from the environment to the brain
doesnt pass thru thalamus
Where are olfactory receptor neurons (ORN) found?
Roof of nasal cavity
Inferior surface of cribiform plate along the nasal septum and medial wall of superior turbinate
How many dendritic processes does the olfactory receptor neuron (CN 1) have?
SINGLE dendritic process
What type of receptors are odorant receptors?
GPCR
what are the components of olfactory histology
- lamina propria
- basal cells
- olfactory receptor neurons
- supporting cells
- brush cells
- cilia
7 mucosa
what does the lamina propria contain
CT w/ immune cells
= exposed to the outside
what are basal cells
layer underneath basement mem
=stem cells & supporting cells
-continuous turnover (30-60 days)
what is the histological representation of brush cells
ciliated columnar epithelial cilia
what are cilia of the epithelium
= nonmotile
contain GPCR odorant receptors that signal to bulbs
what does the mucosa do
hold ORNs
made & secreted by glands & ducts
how many receptors do ORNs project to?
only 1 odorant receptor
but a receptor can get multiple inputs
why are ORNs sensitive to damage with facial trauma
bc of thin bone
how do you sense so many different smells
- ORN able to recognize over 1,000 odorants at small concentrations
- diff combinations of activation –> sense diff smells
what do the olfactory bulbs contain
receptor maps
what is olfactory epithelium
gland & ducts for nasal moisture
-carry info to specific areas of the bulb (receptor map)
what are the layers of the olfactory bulb
- olfactory N layer: axons of ORN
- glomerular layer: ORN synapse on mitral/tuft cells
- external plexiform layer: dendrites of mitral/tuft/granule cells
- mitral cell layer: mitral cell bodies & tuft axons
- granule cell layer: granule cells, principle interneurons of bulbs
what are the steps of olfaction
- odorant contact mucosa & bind GPCR –> adenylyl cyclase –> cAMP –> bind ion channels –> increase Na & Ca influx –> depol/AP –> use ORN to go to bulb
- ORN synapse w/ mitral/tuft cells
- lateral olfactory tract use mitral/tuft cells to get to olfactory cortex (fibers of ant limb of ant commissure)
what are centrifugal fibers
reach bulb via ant commissure
stimulate granule cellls –> (indirectly) decrease mitral/tuft w/ GABA
what are periglomerular cells
inhibit mitral/tuft cells
-help adjust to smell
what does the olfactory cortex do
project to other areas of brain
-paleocortex
how do thalamic nuclei affect smell
help discriminate & identify smell
what is the purpose of the orbitofrontal cortex in olfaction
integrate olfaction, taste & other food cues to help experience flavor
where do olfactory tract fibers project to
- hippo : learn/mem
- lat. hypothal: feeding behavior
- amydgala: identify danger/fear
- ant olfactory nuclei: send info back to bulb & other areas of cortex
- dorsomedial thalamic nuclei: further processing (NOT REQUIRED)
what is anosmia
loss of smell
hyposomia (olfactory hypesthesia)
decrease sensitivity to odorants
ex: nasal polyps in nasal cavity/sinus
ageusia
complete loss of taste
hypoguesia
decrease taste sensitivity
paraguesia/dysgeusia
alter taste perception
could be from drug use
tumor of internal acoustic meatus
loss of ipsi 2/3 of ant tongue
distal genticulate ganaglion
may/may not affect taste
-ipsi paralysis
what are taste buds
sensory organs all throughout oral cavity/pharynx
located in soft palate (innervated by greater superficial petrosal N)
which taste buds are innervated by CN 9
villate papillae
posterior foliate papillae
which taste buds are innervated by CN 10
epiglottis
esophagus
what is taste reception
soluble chemicals that diffuse through taste pores
-chemicals bind on apical microvilli
what is the significance of the pontomedullary jxn for gustation
afferent CN 7 carry chorda tympani
- innervate ant 2/3 of tongue (ant. foliate papillae & fungiform papillae)
what is the path for gustation sensation
sensory cell bodies in geniculate ganglia (CN 7 afferents) –>
carry taste via solitary tract to rostral solitary nucleus –>
2nd order neuron via IPSI central tegmental tract to paricellular VPM –>
3rd order neuron thru IPSI post limb of IC to frontal operculum & ant. insular cortex –> then to rostral Broadmann area 3b (in post central gyrus)
