GA: Taste + Olfaction Flashcards
What is umami taste for?
Amino acids
What are odorant receptors?
GPCRs
When they are deploarized, that AP travels to the olfactory bulb
How does the smell signal go out?
Olfactory receptro neuron –> through lamina propria –> olfactory fila –> cribiform plate –> olfactory bulb
What cells are found in the olfactory glomerular layer?
mitral + tufted cells –> make up the efferent output of the olfactory bulb
Periglomerular cells (small interneurons
What are the 5 layers of the olfactory bulb?
Glomerular Layer
External plexiform layer
Mitral cell layer
Granular cell layer –> contains granule cells –> The principal interneuron of the olfactory bulb
How do granule cells modulate olfactory bulb activity?
Via an inhibitory feedback loop that decreases activtity of mitral + tufted cells
In the olfactory bulb, which cells are inhibitory and which cells are excitatory?
Inhibitory = Periglomerular cell + Granule cell
Excitatory = Mitral + Tufted cells
What is the hallmark of the olfactory bulb?
It projects directly to cortex and DOES NOT relay via thalamus
What forms the lateral olfactory tract?
Mitral + tufted cells
IMPORTANT: the olfactory cortex (on the ventral surface of the telencephalon) includes which areas:
Anterior olfactory nucleus
Olfactory tubercle
Piriform cortex
Anterior cortical amygdaloid nucleus
Periamygdaloid cortex
Lateral entorhinal cortex
PAPA OL(D)
The lateral hypothalamus + hippocampus are important for what?
feeding behavior + learning + taste
What is anosmia?
Loss of smell
What is hyposomia or olfactory hypesthesia?
WHAT YOU HAVE :)
Decreased sensitivity to odorants
-can be from nasal polyps
What type of pathway is the peripheral taste pathway?
General visceral afferent
How does the peripheral taste pathway work for facial N.?
Facial N (chorda tympani + greater petrosal N.) –> geniculate ganglion –> pontomedullary jxn (via intermediate N. –> solitary tract –> solitary nucleus –> gustatory nucleus (rostral portion)
How does the peripheral taste pathway work for the glossopharyngeal N.?
Lingual-tonsillar branch innervates taste buds in papilla –> inferior ganglia (petrosal + nodose) –> gustatory nucleus (rostral portion)
How does the peripheral taste pathway for the vagus N. work?
Superior laryngeal N. innervates taste buds of epiglottis –> inferior ganglia (petrosal + nodose) –> gustatory nucleus (rostral portion)
What is the hallmark of the central taste pathway?
Pathway is ipsilateral
What do taste afferents target?
Rostral (gustatory) nucleus
In the central taste pathway, how do 2nd order neurons and 3rd order neurons travel?
2nd = central tegmental tract –> VPMpc
3rd = Post. limb of IC –> frontal operculum + ant. insular cortex (Brodmann area 3b)
What pathway is responsible for the discrimitory aspects of taste?
solitary nucleus –> VPMpc –> cortex
What happens if you get a lesion of the root of CN 7 (or a tumor in the internal auditory meatus)?
Loss of tast to ant. 2/3 of tongue on Ips. side
Paralysis of Ips. facial muscles
Hyperacusis –> paralysis of stapedius M.
Impaired gland secretion
What happens if you damage the distal geniculate ganglion?
Ips. facial paralysis
maybe taste loss
A complete loss of taste (rare) =
Ageusia
Decreased taste sensitivity =
Hypogeusia
Distortions in the perception of taste (ex. from drug use) =
Parageusia (dysgeusia)
