Chemical Senses 2 (Olfaction) Flashcards
G-protein linked 7 transmembrane proteins
Olfactory receptor proteins
Are GPCRs and expressed in the olfactory epithelium
Odorant receptors
Communicates with the accessory olfactory bulb
Vomeronasal organ
What are the three types of cells in the olfactory epithelium
- olfactory receptor cells
- supporting cells
- basal cells
Each one of these receives input from broad area of olfactory epithelium
Glomerulus
Odors produce this in the olfactory bulb
They produce region specific neural activity
Olfactory epithelium cells that are neurons (unlike taste receptors) with a 4-8 week life cycle
Olfactory receptor cells
There are about 400 of these and 200 of these
400 olfactory receptor cells and 200 glomeruli
Animals use accessary olfactory system, vomeronasal organ to accessary olfactory bulb to hypothalamus to detect these
Pheromones
Olfactory epithelium cells that produce more olfactory receptor cells (like stem cells)
basal cells
Connect to correct before the thalamus, this is different than for other systems
Olfactory tracts
These exhibit population coding, receptors broadly tuned, amount of odorant influences response (each one responds to multiple odorants)
Olfactory receptor proteins
Humans may detect these using main olfactory epithelium using trace amine associated receptors (TAARs)
Pheromones
There are many of these (1200-1400) with 2/3 functional in rats and half function in humans
Olfactory receptor genes
Olfactory receptors have 7 of these regions
Transmembrane regions
Expresses its own receptors (300 in mice, 5 in humans), different from nasal odorant receptor proteins
Vomeronasal organ
Communicates with the main olfactory bulb to detect odorants
Olfactory epithelium
Opening of CNG channels allows these to enter the cell
Ca and Na
Receptor genes are expressed in this way in the brain
Spread out in zones. Different genes expressed in different zones
Higher brain areas connect to these to help modify info and maybe focus on most important info
Olfactory bulbs
Each cell expresses only one of these, also expressed on axons and may help guidance
Olfactory receptor genes
Contain one dendrite and an unmyelinated axon
Olfactory receptor neuron
These are spread out in zones but not clustered within a zone (they all don’t need to be next to each other)
Olfactory receptor proteins
Second order olfactory neurons in each glomerulus
Mitral cells
Taste and smell integration occurs here
Orbitofrontal cortex
Each receives input from only one receptor cell expressing the same receptor gene (red to red, green to green, etc)
Glomerulus
Activated adenylyl cyclase leads to increased this
cAMP
Ca causes these to open
Ca activated Cl channels (Cl leaves the cell)
Humans can detect 100,000’s of different ones of these
Smells of different substances
Synapse on glomeruli in the olfactory bulbs (2000)
Olfactory receptor neurons
Different glomerului respond to different these
Different odors
These receptors are called V1 and V2 receptors and are expressed in the vomeronasal organ
Pheromone receptors
These located in olfactory bulbs communicate and modify input to brain
Glomeruli
How many olfactory cells in humans?
About 400
How many mechanisms are there for smell detection?
One
Olfactory epithelium cells that are like glia
Supporting cells
2nd order neurons leaving the glomeruli
Olfactory tracts
This type of neuron firing pattern may represent odor qualities
Temporal patterns
General pathway of info for olfactory info
olfactory bulb to olfactory tract to olfactory cortex
This creates a map of genes (map of odor info)
Array of glomeruli
These connect to the olfactory bulb through bony plate and has fragile axons that can be easily damaged to produce anosmia
Olfactory receptor neuron
Olfactory connections go to forebrain areas involved in these
Memory, motivation, and emotion (trigger memories/emotions)
The stimulation of Golf activates this
Adenylyl cyclase
25k neurons converge onto 100 second order olfactory neurons (mitral cells ) in each of these
Glomeruli
Tufted cells, periglomerular cells, and granule cells do this in central olfaction pathways
Modify communication
Olfactory receptors on cilia stimulate this
G protein (Golf, only in olfactory cells)
Odorants get dissolved in this
Mucus layer
Spatial representations of odors, common in sensory systems
Olfactory maps
Often requires contact while odorants are more volatile
Pheromone detection
Increased cAMP opens these
cAMP-gated channel (CNG)
All 5 vomeronasal organ receptor genes in humans are this
Pseudogenes - they don’t code for functional proteins
Representation of olfactory info involves this, the combination of responses from many cells
Population coding
A complex mixture of antibodies, proteins, and odorant binding proteins which concentrate odorants to allow us to get a signal
Mucus layer
These two things determine sensitivity, dogs are superior to humans in both areas
Size of olfactory epithelium and number of receptors
These receptors look like taste receptors while these look different
Pheromone receptors look like taste receptors and olfactory receptors look different
How is the cell depolarized in smell detection?
Ca and Na enter and then Cl leaves
These contain axons from the olfactory nerve (cranial nerve I)
Olfactory receptor neuron
This contains three types of cell and is not to be confused with the nose
Olfactory epithelium
Does the smell signal fade quickly? Adaptation?
It fades quickly. Adapt to ignore smell the longer we are in it
Odorants bind to these
Olfactory receptor on cilia