Smell and Taste Flashcards
trigeminal nerve system in the mouth
100-1000x less sensitive than the olfactory system
protective- detect noxious or irritating compounds
capsaicin receptor
ion channel of TRP family (also opened by heat)
capsaicin opens the TRP channel, allowing Na and Ca ions flow into the cell, causing depolarization of noiciceptive fibers and the sensation of pain/heat
sensitivity and discremination of olfactory system
10e-12 to 10e-14 M
can discriminate at least a trillion smells
aging effects on smell
by 50-70, less than 50% of our original capabilities
adds to difficulties w/ appetite and nutrition
anosmia
deficit in the ability to detect specific classes of compounds
odorant based communication
detection of sex hormones elicits sex specific responses in hypothalamus
important in mother/infant recognition
steroid component in male sweat is a pheromone, influencing arousal and mood
vomeronasal organ
pheromone receptor in the roof of the mouth- regresses during development in humans
gross anatomoy of the nasal cavity
3 ridges- conchae
most epithelium is respiratory- ciliated
olfactory receptor cells limited to upper and middle conchae
3 cell types
basal- precursor of receptor cells. average lifespan is only 60 days and complete turnover occurs every 6-8 weeks
support- apical suface w/ microvilli that support receptors
receptors- dendrites projecting to epithelial surface and unmyelinated axon that forms fascicles that eventually become the olfactory nerve before passing through the cribiform plate
olfactory bulb
contains glomeruli- endings of receptor cell axons and mitral cell dendrites
mitral cells
principal projection neurons of the olfactory bulb, and are the only ones to project to other regions of the brain
how do olfactory receptor neurons respond to simulation
change in rate at which fire APs
change is d/t change in conductance of the receptor cell that leads to its depolarization to threshold
signal transduction occurs in cilia.
odorant receptors are g protein coupled receptors w/ 7 transmembrane, which modulate ion channels in cilia
what mechanisms have been implicated in ordorant transduction
change in adenylate cyclase activity and cAMP
production of IP3 and phospholipase C
unclear if they are separate or related mechanisms
there is discrimination and concentration determinatino at the level of individual receptor cells
an olfactory receptor cell may respond to one odorant or many, and thresholds of detection may differ
genes encoding receptor proteins
nearly 1000
largest family is g protein coupled receptors- 7 transmembrane spanning regions
sorting of odorants
among receptors, there are functional groups based off molecular shape organized into different domains of expression in the nasal cavity