Olfactory- complete Flashcards
(30 cards)
Odorants
small, volatile, hydrophobic molecules that bind to olfactory receptor neurons, inhaled from air, travel into to nasal cavity.
Each nasal cavity contains
olfactory sensory epithelium.
odorants bind to olfactory receptor neurons in
OSE or Olfactory sensory Epithelium
What causes transduction of a signal in olf neurons?
odorants binding to olfactory receptor neurons cause transduction in these neuronal cells.
transduction
a physical stimulation is converted to an electrical signal
OSE = Olfactory Sensory Epithelium resembles
respiratory epithelium. nasal passage is anatomically connected to respiratory compartments.
OSE consists of what kind of cells?
- pseudo stratified columnar epithelium
- with a ciliated apical portion
The major difference between olfactory and respiratory epithelium
no neuronal component in respiratory; Cilia of OSE has receptors for odorants and the cilia processes extend into mucus layer
OSE contains these cells
support cells + basal cells (give rise to the olfaction cells)
location of OSE in relation to palate, olf bulb and plate
OSE is superior to the palate, olfactory bulb sits superior to the cribriform plate. cilia from the olfactory cells are embedded in the mucus layer
How are OSE cells connected to the higher neuron structures?
- Axons from olfactory receptor cells (in OSE) protrude through the cribriform plate of the ethmoid bone
- Then axons fasciculate/converge to form olfactory nerves
- Olf nerves travel to the olfactory bulb.
- Olf Bulb gives rise to olf tracts
Olfactory receptor cells/neurons
highly differentiated; each odorant receptor neuron (ORN) expresses 1 odorant receptor type, so only sensitive to a subset of odorants.
One odorant can activate
combination of different receptors
What gives olfaction its high degree of plasticity?
- 1 odorants can activate different receptors
- smells cause different degree of activation of certain receptor types.
Signal transduction in ORNs
** Mediated by GCPRs**
- Odorants bind G-alpha olf GCPR
- activates adenylyl cyclase –> activates cAMP-> intracellular cAMP inc
- cAMP binds + opens cyclic nucleotide gated (CNG) cation channels (nonselective: Na+ and Ca+ can flow in, Cl- can flow out).
- Cations in/ anions out = depolarization of ORN
What causes depolarization of ORNs? AP?
1) Odorant binding increases intracellular cAMP
2) cAMP gated cation channels open [nonselective ch, Na+ and Ca+ can flow in, Cl- can flow out].
3) Cations in/ anions out (negative leaving cell) = depolarization!
4) If depol reaches threshold, AP occurs in the olf cells, and is transmitted to the olfactory nerves.
*(cAMP gated ch = cyclic nucleotide gated = CNG)
Topography of the Olfactory Bulb
Within the bulb are glomeruli = specialized cluster of synapses. Convergence of 1 type of olfactory receptor cells/glomerulus.
Topography is preserved in _____ but not ___
preserved in amygdala, but not in the piriform cortex.
Also synapsing within the glomeruli are
mitral and tufted cells.
Which cells within the olf bulb gives rise to the lateral tracts?
Mitral and tufted cells give rise to lateral olfactory tracts that go the olfactory cortex.
bilateral symmetry means what?
The Olfactory bulb exhibits bilateral symmetry, so each side leads to a lateral tract. No crossing over, except the occasional mitral cell collateral.
periglomerular cells
support cells within the olfactory bulb
Info from Olfactory Bulb is sent to these targets:
1) piriform cortex- main target tissue.
2) amygdala- important for emotional memory and the limbic system.
3) hippocampus- major input, associated with memory, learning.
4) olfactory tubercle
5) Entorhinal cortex (–> hippo)
How does thalamus receive olfactory input?
indirect input from the olfactory bulb, via amygdala.
