Neuroscience - Smell/taste Flashcards
what is olfaction
detection of airborne molecules
what is gustation
information about ingested substances
chemical and physical qualities
where are sensory receptors located
olfactory epithelium
where do the olfactory afferent fibres project to
directly to the olfactory bulb in the CNS
what are olfactory neurones
bipolar
name structural features of the olfactory epithelium
unmyelinated sensory afferent
mucus layer
specialised cilia embedded in the mucus layer
how long does olfactory neurone damage last for
6-8 weeks
what produces the mucus in the olfactory lobe and what is its function
bowman’s gland
concentrates the chemicals and brings them into contact with the cilia
what is the function of dividing stem cells in the olfactory epithelium
allow replacement of damaged olfactory neurones
what are the G-proteins within olfactory cilia
G-olf
what does odorant transduction lead to
cascade of chemical reactions leading to influx of Na+ and Ca2+ leading to depolarisation
what does the olfactory receptor processes pass through
cribriform plate and enter the olfactory lobe
how are different olfactory receptors selective for different odors
some GCPR’s are more receptive to some airborne chemicals than to others
may or not produce an action potential
how are airborne chemicals distinguished from eachother
the pattern of of different types of olfactory neurones that do and don’t produce an action potential in the presence of the odor
what is the olfactory bulb composed of
mitral cells - olfactory tract
glomeruli - convergence and amplification
where do the axons of the mitral cell project
from the olfactory bulb to accessory olfactory nuclei
the relationship between one odorant neurone and one glomeruli enables what
allows specific regions of the olfactory bulb to respond to different chemicals
what is the major target of the lateral olfactory tract
piriform cortex
what are the neurones in the pyriphorm cortex
pyramidal neurones - glutamatergic
what are taste papilae
specialised invaginations on the surface of the tounge
what are the different types of taste papilae
filiform papillae
fungiform papillae
circumvallate
follate papillae
which taste papillae hast no taste buds associated with it
filiform papillae
how many taste buds does the fungiform and circumvallate contain
fungiform - 3 on the apical side
circumvallate - 250 in the trench
how are follate papillae organised and how many taste buds do the contain
into parallel ridges
600
what is the function of microvilli on the tips of taste cells
increase the surface area that molecules can interact with that taste cells
at the apical microvilli, what protein receptors detect what
ion channels - salt and sour/acids
GPCR - sweet, bitter and umami
where do the taste efferent neurones project to
the facial (VII)
glossopharyngeal (IX)
vagus (X)
what are the transmitters involved in taste
serotonin and ATP
what detects sweet and umami
T1 receptors
what is the key secondary messenger in signalling for sucrose, glutamate and quinine
phospholipase beta 2
outline the basic transduction of sweetness
detected by T1R2/T1R3
activation of PLC beta 2
outline the basic transduction of umami
detected by T1R1/T1R3
activation of PLC beta 2
what is the half maximal concentration of glutamate
0.3mM/L
outline the basic signalling pathway for biterness
detected by T2R receptors
expresses alpha-gustducin
activation of PLC beta 2
what nerves project from the tongue
cranial nerve VII - facial nerve and chorda tympani
what nerves project from the back of the tongue
cranial nerve IX - lingual branch of the glossopharyngeal nerve
what nerves project from the epiglottis and oesophagus
cranial nerve X - superior laryngeal branch of the vagus nerve
where does cranial nerve VII project to
the rostral part of the gustatory nucleus
where does cranial nerve IX project to
the mid region of the gustatory nucleus
where does cranial nerve X project to
caudal region of the gustatory nucleus
what is 2nd order signalling of gustation
from the gustatory nucleus to the ventral posterior medial nucleus (VPM)
what is 3rd order signalling of gustation
signalling from the VPM to the gustatory cortex - insular and orbitofrontal cortex
where in the higher centres of the brain is salt detected
insular cortex
what is the function of the orbitofrontal cortex
gives us our perception of food
involved in signalling for satiety
