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67 Cards in this Set

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  • Back
Why when presented with a mixture of red and green do we see yellow?
Because red causes LATERAL INHIBITION of green, and green causes LATERAL INHIBITION of red and so we see yellow.
Do we have yellow photoreceptors?
No; only blue/green/red
where are our olfactory receptors located?
In olfactory epithelium (mucosa)
how many olfactory receptors in humans?
10 million
What are olfactory receptors?
Bipolar brain cells - neurons - unique because they are the only part of the brain that actually comes in contact w/ the outside world.
What are olfactory receptors related to?
Highly differentiated epithelial cells.
What makes up the receptor component of bipolar epithelial olfactory neurons?
An apical dendrite extending to the epithelial surface, expanded into a knob.
Where are the actual receptor molecules for olfactory neurons?
In cilia extending up out of the knob.
How are bipolar olfactory receptor neurons connected to the brain?
By a basal axon extending thru the cribiform plate to synapse with the olfactory bulb.
What are the receptor molecules in olfactory cilia?
a large gene family of oderant receptor molecules - 1 type is expressed per neuron.
What type of receptors are the oderant receptors?
7 transmembrane Gprotein coupled
4 different celltypes contained in the olfactory mucosa/epithelium:
1. Receptor cells (bipolars)
2. Free nerve endings
3. Support cells
4. Basal cells
What do the free nerve endings do?
Detect sensations like tingling of menthol/ozone in mountain air
What do support cells do?
Secrete mucus
What do basal cells do?
Cell turnover
Lifespan of olfactory neurons:
1-2 months
What happens if you have a severe blow to the head?
It can shear off all olfactory receptors, but b/c you have basal cells you can regain sense of smell within 1-2 months.
Axons of the olfactory bipolar cells project to:
The olfactory bulb
What 4 cells are in the olfactory bulb? Functions?
1. Periglomerial (local lateral inhibition)
2. Granule (local lat inhib)
3. Tufted cells - output
4. Mitral cells - output
How do the olfactory axons of bipolar cells get to the olfactory bulb?
By penetrating the cribiform plate
First layer of cells in the olf bulb (after penetrating crib pt)
Periglomerular cells
What cells are just interior to the periglomerular cells?
Tufted and Mitral
What lies below the mitral layer?
Granule cells in the granule layer
What are Tufted and Mitral cells?
Output cells form bulb to olfactory tract.
What is the function of mitral cells?
MAJOR OUTPUT of olfactory bulb into the olfactory tract
-Recieve signal from incoming olfactory nerve fibers - synpse at glomeruli
How many areas of the brain receive olfactory messages? What are they?
-Anterior olfactory nucleus
-Olf tubercle (ant perf subst)
-Pyriform cortex
-Amygdaloid complex
-Enterorhinal Cortex
How are smells localized?
By communication of the two olfactory bulbs via their projections to the cortex
What 2 major components of smell make this sensation distinct?
Function of the anterior olfactory nucleus:
Communication between the two bulbs - allows LOCALIZATION of particular smells by comparison
Where is the anterior olfactory nucleus?
In the anterior commissure
Function of the olfactory tubercle:
Conscious perception of smell
Another name for olfactory tubercle:
Anterior perforated substance
Where is the olfactory tubercle located? What does it project to?
-Located behind olf tract
-Projects to Medial dorsal nucleus of thalamus
-Then to orbital frontal cortex
What does the pyriform cortex consist of?
Anterior uncus
Anterior parahippocampal gyrus
Function of pyriform cortex:
Olfactory discrimination
Function of amygdaloid complex:
-Emotional component of smell
-Autonomic activity
-Endocrine activity
Where is the entorhinal cortex?
The parahippocampal gyrus
What is the main olfactory cortex?
What is secondary?
Main: Pyriform (uncus/ant PHC)
2ndry: Entorhinal
Where does the entorhinal cortex project to?
The hippocampus
Function of hippocampus in olfaction:
Memory function
Function of pyriform cortex:
smell discrimination
Function of hippocampus:
Memory of smells
Function of orbital frontal cortex and the thalamic component of olfaction:
Conscious awareness of smells
What is the nature of all molecules that you can smell?
They must be fat soluble to penetrate the submucosa and bind trnasmembrane gprotein receptors.
What determines which oderant receptor will be bound by a stimulant?
-Chemical properties of the oderant stimulus
What encodes stimulus quality of olfaction?
Labeled line codes - specific for individual smells.
How does smell sensation differ from vision?
There isn't cancelling out of smells - smell cookies and pizza baking both.
Where are taste buds located?
-Upper 1/3 of esophagus
4 Cell types in the taste bud:
-Support (glial)
-Receptor cells
-Basal (regenerative)
-Afferent fiber
What is the major difference of taste receptors compared to smell?
Taste receptors have no apical dendrite to take info to a bipolar cell; rather they need an afferent fiber
Where does the afferent fiber for taste sensation go?
to the CNS
5 types of taste sensation
-Umami (msg)
Nerve for Taste from anterior tongue:
Facial VII - chorda tympani
Nerve for Taste from posterior tongue:
Glossopharyngeal - IX - via lingual branch
Nerve for Taste from epiglottis / upper 1/3 esophagus:
Vagus - X - laryngeal branch
Where do the nerve fibers carrying taste sensation from the buds go?
Solitary nucleus of medulla
Where does the STN of medulla project?
VPM nucleus of the Thalamus
Where does taste input travel from the thalamus VPM?
Two places:
1. Gustatory region of Postcentral gyrus
2. Insula
Function of the insula:
Conscious taste perception - you become very concious of it as you carefully pry open the insula and WHAM out pops the tongue sticking out at you.
What is the specific Gprotein for taste?
3 features of taste encoding:
-Broadly tuned receptors
-Labeled lines
-Taste modification / adaptation
What is taste adaptation?
The change in sourness of lemonade as sugar is added
What is taste modification?
Brushing your teeth right after eating orange juice - makes the OJ seem more sour.
What is sour?
Acid - HCl
What is Salt?
What is bitter?
How do we get taste adaptation and modification?
By lateral inhibition.