Lecture #17 Flashcards
what are the there systems that allow for the interaction and recognition of airborne signals?
olfactory, vomero-nasal, and gustatory
what does the olfactory system apply to?
deals with odorants
what does the vomero-nasal organ apply to?
designed to detect pheromones shared by many species (not humans)
what is the goal of the olfactory system?
to manage airborne molecules (odorants) that are fundamental to give information about other animal / plants and to detect noxious substances
what is the goal of the voter-nasal system?
to recognize predators
what the main nerves of the olfactory system?
olfactory receptor neurons (ORNs)
describe the localization of ORNs:
the cell body is located in the periphery (especially in the nose mucosa) while the axons forth nerve 1 (olfactory nerve) and move from the periphery to the CNS through the cribriform plate
what protects the ORNs?
a huge amount of mucus produced by the mucosal cells - others the nerves would be directly exposed to the neural cavity
where is the first synapse of the olfactory bulb?
in the glomerular region
where does the information travel first from the olfactory division?
directly contacts regions of the cerebral cortex, such as the piriform cortex, olfactory cortex, and the amygdala
does the olfactory stimulation reach the thalamus?
the input signal goes directly to the brain and then it can be transmitted to the thalamus
what is a unique characteristic of this sensory system?
the absence of a topographic map
what is a lack of olfactory sensation called?
anosmia
what can cause anosmia?
elicited by specific mutations involved in signal transduction and in the generation of trains of action potential
what diseases can trigger an alteration of our sense of smell?
- Alzheimers
- early sign of Parkinsons
- schizophrenia or bipolar disorders can experience olfactory hallucinations
what are the accessory and supporting cells in the mucosa?
form the Bowman glads releasing mucus and supporting cells are also present both on the slide of the ORNs and on the basolateral part of the epithelium
what is unique about the sensory system in the CNS?
these neurons can regenerate
what is different between mice and humans in regards to the olfactory system?
some cells are locally generated, so when dealing with olfactory receptors that are between the cribriform plate and the olfactory mucosal region, were are not dealing with neural stem cells derived from the SVZ - they are regenerated ORNs → can grow and send their axons to the cribriform plate and are unmyelinated
in humans regeneration is debated
describe ORNs:
transmembrane proteins that are classical G-coupled protein receptors containing several variable domains in both the N-terminal region, extracellular loop, and intermembrane domains
in mammals, what is unique about the ordorant receptor gene family?
it is the largest known single gene family representing 3-5% of the genome
describe the molecular mechanism of odorant transduction:
molecular cascade starts with the interaction of the odorant with the G-coupled protein receptor G(olf)
activation leads to the activation of adenylyl cyclase III localized on the inner side of the pm (responsible for the conversion of ATP to cAMP)
conversion activates the cAMP-gated ion channels allowing the entry of sodium and calcium inside the cell leading to the depolarization of the membrane
what is the olfactory receptor in the CNS?
glomeruli - regions receive axons of individual ORNs
describer the mitral cells of the olfactory bulb:
extend a short cytoplasmic dendrite tot the glomerulus and a long axon to contact the piriform cortex, amygdala, or other cortical nuclei
in this case the crossing of the midline does not occur, these cells start from the olfactory bulb and sent axons to the ipsilateral side
what cells flank the mitral cells?
tufted cells
what are the function of tufted cells?
involved olfactory perception (although the mitral cells are still the main cells involved)
how do the granule cells interact with the mitral cells?
they are di-dentritic cells that only express dendrites and they flank the mitral cells
inhibitory → constitute the innermost layer of the vertebrate olfactory bulb and synapse primarily on the basal dendrites of the mitral cells in the external plexiform layer
what cells flank the glomerulus?
periglomerular cells
describe the activation of the glomeruli in response to complex odors?
there is thee activation of few glomeruli but the reason is unknown
where is the vomeronasal organ located?
laterally under the gumline
what is another name for the vomeronasal organ (VNO)?
Jacobson’s organ
what do mammals use the VNO for?
can sense the odorants of predators and extert homeostatic or aggressive responses when that odor is perceived
what is detected by the VNO?
pheromones → called kairomones in animals
do humans have the VNO?
no → we can somehow still detect pheromones but is is unsure how
describe the vomeronasal receptors:
g-couples protein transmembrane receptors called V1R and V2R
TRP is one of the ion channel involved in the perception of pheromones (also involved in the detection of temperature)
