Special Senses: Smell and Taste Flashcards
Why is it that we can smell natural gas?
Mercaptan is added to the natural gas into order to alert us to the presence of natural gas.
**** Natural Gas does not normally have an odor!
How many odorant receptors do Humans express?
350 different odorant receptors
(Tend to be in different classes)
Describe the signal transduction process of Smell.
What happens if a smell persists for a few minutes?
- Odorant will bind to a G-PROTEIN COUPLED RECEPTOR
- Golf (Gs protein that is specific to olfactory receptors) will bind to Adenylyl Cyclase which will activate cAMP
- cAMP will bind to a channel and cause it to OPEN!
- Na+ and Ca2+ will come INTO the cell
**** If an odorant persists for more than a few minutes, the sensitivity of the channel to cAMP is REDUCED!!!! You will not get as many action potentials. This is due to the Olfactory CORTEX sending signals BACK to the Olfactory Receptors!
**** Odorant Receptors are expressed on EVERY cilia on a SPECIFIC Olfactory Neuron
Why do things smell differently when you have a cold?
Some smells are going to be preserved but you will not get ALL of the odorant receptors activated like you normally would without a cold.
**** Different Odorant Receptors are distributed throughout the Olfactory Epithelium
Describe how we can perceive different smells.
Each odorant activates a DIFFERENT COMBINATION of odorant receptors to produce its characteristic odor!
*** Odorant concentration changes the perceived smell! (At HIGHER concentrations, the odorant starts to bind to receptors with a lower affinity for the odorant in addtion to the receptors with a higher affinity)
Describe the Trace Amine-Associated Receptors (TAARs).
Second but smaller set of odorant receptors
Activation of these does not necessarily lead to conscious awareness of an odor and seem, instead, to produce physiologic/endocrine responses to PHEROMONES
Through which structure do the olfactory neurons pass in order to get to the Olfactory Epithelium?
Cribriform Plate
List the different cells that are in the Olfactory Bulb
- *Cells:**
1. Granule Cell (Remain in olfactory bulb)
2. Mitral Cell
3. Tufted Cell
4. Periglomerular Cell
Describe the various Post-Synaptic neurons within the Olfactory Bulb.
*** Within the Olfactory Bulb, we find glomeruli, where the axon terminals from olfactory neurons synapse and release EAA on the dendritic trees of the post-synaptic neurons.
Post-Synpatic Neurons:
- Mitral Cells (Axons will go to Olfactory CORTEX)
- Tufted Cells (Axons will go to Olfactory CORTEX)
- Periglomerular Cells (Axons remain in the olfactory bulb) –> Work between the different Glomeruli!
What is the purpose of the Glomeruli in the Olfactory Bulb?
All the axons from the olfactory neurons expressing the same odorant receptor converge on two glomeruli located in the ipsilateral olfactory bulb.
Describe the different functions for axons from the Mitral, Tufted, Periglomerular, and Granule Cells.
- Mitral and Tufted Cells –> Join the Olfactory Tract and relay Olfactory information to the Brain
- Periglomerular Cells –> Release GABA at their synaptic contacts with other glomeruli and inhibit the activity from those glomeruli. Help DISTINGUISH between different smells!
- Granular Cells –> Release GABA at their synapse with mitral and tufted cells. Their job is to INCREASE the specificity of the the message going to the Olfactory Cortex
What is the first possible synapse in the Olfactory Cortex?
Anterior Olfactory Nucleus
What are the different components of the Olfactory Cortex?
- Anterior Olfactory Nucleus
- Piriform Cortex –> Determining how we interpret smells
- Anterior Cortical Amygdaloid Nucleus –> Emotional connections
- Periamygdaloid Cortex
- Lateral Entorhinal cortex
What is the purpose of the Entorhinal Cortex?
Entorhinal Cortex: Branches that send axons from the Olfactory Neurons into the HIPPOCAMPUS which is crucial in memory formation and memory recall
Describe the purpose of the Piriform Cortex.
Piriform Cortex: Projects to the LATERAL HYPOTHALAMUS, which is important in control of appetite!
- Also projects to MEDIAL ORBITOFRONTAL CORTEX to provide information that will be used to identify the FLAVOR of foods
Describe the various synapses involved in the Gustatory pathway to the brain.
Syanpse in:
1. Nucleus tractus solitarius –> Axons from Tongue will come and synapse here! Part is devoted to Gustation and other part is devoted to Respiration (lungs)
- Thalamus –> From the Thalamus, axons go to the CORTEX AND to the LATERAL HYPOTHALAMUS (has a significant impact on appetite)
- Gustatory Cortex –> Involved in identifying the basic taste and innate responses such as attraction to sweet tastes or aversion to bitter tastes
