Piri Lecture 2 Olfactory

Hyposmia

Decreased ability to smell

Humans are sensitive to odors and our ability to detect different odorants depends on the odor at we are trying to detect, give some examples of this.

Detection of ozone can be detected by higher amount of parts per billion compared to D-limonene which can be detected with smaller amounts.

How do we identify which odorant is present?

Different neurons respond to different types of odorants thus we get 3 neurons and have 3 different odorants and see how membrane current and time respond to these neurons. We can also study the adaptation rate and identification rate of how quick we can identify odorant.

What can we see in population coding scheme for olfactory?

Each receptor cell expresses one olfactory receptor protein Different cell respond to different odors with different preferences Deifferent receptor cells are scattered within olfactory epithelium

T/F Most olfactory fibers end in the amygdala and the hippocampus where they are processed.

False Most olfactory fibers are sent to the amygdala and the the cortex.

T/F There is topographic mapping in the perform cortex for olfactory response like other stimuli such as taste, and hearing.

False Puriform cortex we dont see tomographical graph. no geographical localization, same for different odorants.

T/F Dysosmia is the lack of the ability to smell some odorants.

False The distorted sense of smell

T/F The olfactory impulses are only sent to parts where no other sensory information is received such as vision,taste,etc.

False The olfactory cortex and the amygdala forward olfactory impulses to other parts of the brain to integrate olfactory with other sensory information

T/F Mammalian genes have introns in the odorant receptor protein.

False they Don't have introns

T/F Olfactory receptors cannot be renewed over life time.

False they can, they are the only type of neurons

T/F The sex of the human does not matter in response to the activation of the brain, meaning that both sex have the same area of activation in the brain.

False, Men and women have different activation areas. An example is for men you have the posterior hypothalamus while and women the anterior hypothalamus

T/F Information is sent to the thalamus first and then to other areas of the brain such as the cortex.

False, the information sent to the cortex is not sent via the thalamus.

T/F Olfactory epithelium and respiratory epithelium are the same tissue

False, they do not express the same proteins.the picture on the left shows that Forkhead 1 (transcription factor) is highly expressed in respiratory epithelial cells whereas not expressed in olfactory cells.

What is the name of the structure when the olfactory receptor cell and second-order olfactory neuron synapse together?

Glomerulus/Glomeruli

Fill in the blank In glomerulus about __ axons of olfactory receptors converge and synapse upon dendrites of about __ second-order olfactory neurons which send axons to the brain

In glomerulus about 25000 axons of olfactory receptors converge and synapse upon dendrites of about 100 second-order olfactory neurons which send axons to the brain.

How does dysosmia occur?

Infected nasal sinuses and damage to the olfactory bulbs can cause dysosmia.

Another way that phantosmia can be induced.

It can also be induced by epilepsy affecting the olfactory cortex.

What other mental conditions can be accompanied by dysosmia.

Mental conditions such as depression and schizophrenia may be accompanied by dysosmia.

Do we think about odor to be pleasant because two areas are activated instead of one or its a chemical structure which leads to activation of the cingulate and orbitofrontal cortex and tells us is pleasant or unpleasant.

Might be on test. Think about it. (ANSWER IF YOU CAN AMOR)

Which is the main cell that connected with olfactory receptor neurons?

Mitral cell is the main cell.Most projections to the olfactory tract are provided by mitrals cells.

What are the most common odors?

Most unpleasant

What is the stimulus for olfaction

Oderants

How does olfactory transduction occur when odorant molecules are present?

Odorant molecules bind to odorant receptor protein which are bind to G olfactory-coupled receptor protein which activate Adenylyl cyclase. This AC convert ATP to cAMP. AMP activates cation channels to open up and let influx of Na+ and Ca2+ to come in. Ca2+ then bind to Chloride channels to open and Cl- go out of the cell which depolarizes membrane and send the signal to the olfactory nerve axon and to the olfactory bulb and into the CNS.

How does phantosmia occur?

Often results from damage to the nervous tissue in the olfactory system caused by viral infection, trauma, surgery, or exposure to toxins or drugs

Where are the cells that are sensitive to odor located?

Olfactory epithelia's

The Cilia is attached to what

Olfactory knob

Give an example based on the above question.

Olfactory receptor neuron Green is expressing receptor protein for green apple odorant, then all of the green receptor cells will converge to the same glomerulus. There will be 1 or 2 glomeruli that wil receive the same olfactory receptors (bind to the same types of receptors) Meaning there will be 1 or two glomeruli that will have the green olfactory receptor cells.

Fill in the blank. __________ and ________ cells (inhibitory interneurons) modulate the activity of the mitral and tufted cells.

Periglomerular and granule cells (inhibitory interneurons) modulate the activity of the mitral and tufted cells

"hallucinated smell"

Phastosmia --fantasma que no existe--

Based on the last two responses, and based on olfactory mechanisms that provide information about olfactory stimulus we can see that what type of coding is olfactory reception?

Population coding, different oderants stimulate different neurons, not just particular one

What is the cortex called that cortical regions in the temporal lobe that receive fibers from the olfactory bulb

Primary olfactory cortex

What are these different areas that the olfactory bulb sends

Pyriform cortex Olfactory tubercle Amygdala

Is the membrane protein conserved or non-conserved?

Som are areas are conserved and some are non-conserved. You need conserved areas because you need to respond to different chemicals.

How can concentration affect sensitivity to odors?Give an example.

Some odors at lower levels can be pleasant and in higher levels it can be unpleasant. An example is low level concentration of indole can be pleasant due to the smell of floral but in high amount concentration of indole can be unpleasant and can be putrid (rotting).

What is another method in which we can identify olfactory as a population coding.

Temporal Spiking Pattern, based on the degree of spiking such as time, if it was after or before the odorant came into contact.

What does the top answer mean in terms of connections?

That there is alot of convergence

Describe in a summary what happens when we breath chemicals?

The air contains different chemicals and once get into contact with cilla of olfactory receptors, theey can be activated and axons project to olfactory bulb and then neurons project to different areas

What is the importance of the glomerulus and the olfactory receptor neurons?

The important thing, those olfactory neurons that express certain olfactory receptors make connections with second order neurons in the same glomerulus.

Congenital anosmia

The lack of the sense of smell at birth. Usually due to genetic factors

Fill in the blank. The _____ and _____ cells are excited by the inputs from the olfactory sensory neurons.

The mitral and tufted cells are excited by the inputs from the olfactory sensory neurons

Why is the reason that animals have better smell than others?

The number of olfactory receptors neurons this sends more connections to the brain and have much larger brain area that analyzes that information.

What does the basal cell do?

They are dividing cells that contribute to the growth of the new olfactory receptors

What does the bowman's gland do?

They produce the mucus where the chemicals are dissolved in.

Where does the olfactory receptor cells send there axons to?

They send the axons to the olfactory bulb, which the olfactory bulb contain the secondary order olfactory neuron. When these two (olfactory receptor cell and the second order olfactory neuron) synapse together

T/F Anosmia may be an early sign of degenerative brain diseases such as Parkinson's and Alzheimer's.

True

T/F Olfactory neurons are true neurons

True

T/F Responses of chemically distinct odorant respond to individual glomeruli.

True 1 or 2 glomeruli activate based on the distinct odorant thus being CONCENTRATION DEPENDENT.

T/F Taste receptors are continuously renewed

True Every 4 weeks

What are the different cells found in the olfactory bulb that are attached to the glomeruli?

Tufted cell Mitral cell Granule cell Periglomerular cell

Based on the last question, discuss the diagram with your partner about how is figure is population coding.

We can identify that each receptor can identify different odorants like the green cell has different receptors that can be activated based on the odarant of citrus, floral, peppermint, but not almond. We can also see the degree of stimulus the green cell has on the different odarants, timing, and adaptation. They respond to multiple stimuli (odorants) at the same time.

Based on the last answer describe what is happening in this figure.

We can see that for neuron 1, it is stimulated by all three odarants (cineole, isoamyl acetate, acetophenone) but it has a different degree of response and adaption. For neuron 2 we have only stimulated by cineole but affected in time. Neuron 3 is stimulated by isoamyl acetate and acetophenone. This is an example of different neurons respond to different odorants.

Can glomeruli be activated in a higher or lower response based on the percent of odorant? Give an example.

Yes, they can be activated higher or lower response. When exposed with 1% of acetophenone- (sweatness), some glomeruli light up and with higher percentge respond more stronger response by the glomeruli. Thus being concentration dependent.

What does this image show?

activity in the cells is diminished in age but geographically the same place is still seen

Give an experiment where it shows that cilia are responsible for stimulation of olfactory cells.

apply odorant to the cilia and see that the membrane potential is changing but when you add odorant to the cell you dont witness a change—proof it's the cilia

Loss of olfactory sensitivity can be seen in what type of group age in humans? Give an example of how it affected.

by age 70 about 30 percent cannot identiy the correct smell

On brain scan, how can we notice which odor is pleasant or unpleasant?

different areas light up for pleasant versus unpleasant odors —for pleasant odors cingulate cortex and orbitofrontal cortex is activated. whereas for unpleasant odor,

What is the central olfactory pathways, start from the mitral cells and tufted cells all the way to the prefrontal cortex (neocortex)?

he axons of mitral and tufted cells form the olfactory tracts to form the LATERAL olfactory tract and enter several regions of the forebrain. Some are sent to the puriform cortex which then go across the thalamus and into the neocortex. There are others that are sent instead of the piriform into the amygdala or entorhinal cortex to the neocortex.

Give a brief summary of stimulation of olfactory neurons

odorant is dissolved in mucus when it is in contact with the cilia and then sends info to the dendrite and then the cell body. Next the olfactory nerve and then the bulb.Then is sent to different areas of the brain

Give two examples where some medication affect the sense of smell?

1930s 500 children tested zinc sulfate for polio was discovered to kill olfactory senses 1900s Zicam for rhinovirus (regular cold) and can kill olfactory senses, more than 10 years to ban drug, zicam gel was banned This shows that two different studies; polio=zinc and cold (flu)=zicam have the same response kills olfactory receptors

How many glomeruli are there in a bulb?

2000 glomeruli

How many are psedogenes?

60 percent of 950 are psedogenes.

How many proteins does the are there in the olfactory receptor?

7 transmembrane proteins and has 7 domains

How many receptor genes that can detect different odors?

950 genes

What causes permanent loss of smell.

A permanent loss of smell may be caused by death of olfactory receptor neurons, olfactory nerve or brain areas that process smell.

Stuffy nose causes

A temporary loss of smell can be caused by a stuffy nose or infection

Lack of ability to smell

Anosmia

Give a brief summary how anosmic are affected by odor?

Anosmics-people cant detect smell compared to normal subjects, present 7 different odors, most people normal can detect the smell. most than 50 percent with anosmic cannot.

As seen in this figure, describe how temporal spiking pattern can be distinguish for population coding for olfactory

Based on this figure, it shown that the odorant is the stimulus is the apple odor and we see that different cells have a different pattern of spike. Some spike right after they get the stimulus but stop very quickly, some stop responding when the neuron is in contact and some keep on firing even when the stimulus (apple odor) is not present. This plays important role when the brain is tring to distiguish different odorants based on the spiking activity and timing it comes up with certain answer. This is why population coding is seen in this system.

What is another way of changing the odor of the chemical?

By changing the chemistry we can change the odor. An example is a chemical can smell like spearmint but change molecule and get caraway.