Olfactory System: Anatomy and Physiology, Pathways, Animation.
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- čas přidán 2. 08. 2024
- Physiology of Smell. Olfaction: A&P of special senses - sense of smell; loss of smell - anosmia; clinical significance.
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Voice by : Marty Henne
The olfactory system is responsible for the sense of smell, or olfaction. Basically, airborne molecules emitted by an odorant source are detected by olfactory sensory neurons located at the roof of the nasal cavity. These neurons convert chemical stimuli into electrical signals and send them via the olfactory nerve to the olfactory bulb, then to the brain, where they are interpreted as odors.
Odorant molecules are first dissolved in the mucus secreted by the olfactory epithelium, which guides them to the cilia of olfactory neurons. This is where odorant molecules bind to their receptors. Each neuron expresses a single type of protein receptor. There are only about 400 different receptors in humans, but they are used in a combinatorial way such that one odorant can bind several receptors, and one receptor can bind several odorants. This enables the olfactory system to recognize an enormous number of odorants.
Odorant receptors are G protein-coupled. Upon binding to the odorant, a signaling cascade is activated, leading to membrane depolarization. When the olfactory stimulus is strong enough, action potentials are generated and conducted along the axon to the olfactory bulb.
The axons of all olfactory sensory neurons form the olfactory nerve, also known as cranial nerve I. In the olfactory bulb, these axons synapse with second-order neurons - the mitral and tufted cells, within structures called glomeruli. Each glomerulus receives axons from sensory neurons that express the same protein receptor.
The second-order neurons are stimulated by sensory neurons, but they also receive inhibitory feedback from the cerebral cortex. This means an odor can be perceived differently under different circumstances. For example, the smell of food is more appealing when one is hungry, and is less so when one is full.
The axons of mitral and tufted cells form the olfactory tracts, which project directly to the primary olfactory cortex. The primary olfactory cortex is not one but several cortical areas located on the base of the frontal lobe and inferior surface of the temporal lobe. These primary regions then project further to some other areas of the brain, mediating different aspects of odor recognition and response.
Because olfactory neurons are exposed directly to the noxious external environment, they are replaced more often than other neurons. Stem cells in the epithelium differentiate into new olfactory neurons, whose axons grow along the existing axons to the olfactory bulb. Any factors that destroy all olfactory neurons at once would result in permanent loss of sense of smell, a condition known as anosmia. Illnesses that cause inflammation of the nasal mucosa may lead to transient anosmia. Loss of smell also affects the taste experience, as taste and smell are the 2 aspects of flavor.
The ability to smell decreases with normal aging, but anosmia is also an early sign of several neurodegenerative disorders.
Because epileptic seizures often originate from the brain area associated with the olfactory cortex, seizures are often preceded by hallucinations of disagreeable odors.
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Wow, subjects like these in medicine just blow my mind
Simple and straight to the pint . Thankyou man
Thank you this was so useful for study. Simple yet explamatory, perfect.
I've seen quite a few videos on olfactory subjects; this is one of the best!
really the best video for us , students who are going to be doctors 👍😊
Wonderful education! Many thanks!
All the best. Incredible view
Simple to follow and understand while still presenting enough infos. Thanks alot!
What a precise video ....thank you for this
Thank you so much, Doctor/Professor.
Very nice presentation. Definitely great quality. Thank You
Good review👍
Damn, not even my A&P instructor could explain as well and clear as this video. Again thank you so much for this!
same tbh we didn't even go this deep in my class, but its still helpful anyways.👌
Great video.! Really helpful:)
very well explained sir! thank u very much
Excellent video! Thanks.
thank you so much! This was very helpful!! c:
A very interesting video in my opinion.
I had the cauterisation done in the area when I was 15 to stop my nosebleeds.
Well done to you all 😊
Never thought about the fact that we have neurons in parts of the body other than the brain. Fascinating!
Fantastic video, very well and clearly explained
absolutely amazing. as USUAL
Thank you!
it is very well explation and easily got it.that is very helpfull..
Best revision 🥂
Yes yes I can understand ❤️❤️👍🏾
So brilliant explained! Thanku!
Most welcome!
Excellent
Thanks
Very usefule
Thank you sir 😊
Could someone lose their loss of taste after a stroke? If so would the nerves, if damaged be ever repaired or will the taste buds be forever? Thank you in advance.
Really thank ❤
Kya baat hai sir ji
Euuu model ❤️❤️❤️
Thank uu
So should I stop blowing my nose constantly then? My nose is dry
Whether it's a gpcr or even ionotropic receptor, the end result is the same - depolarisation, action potential and inhibitory or excitatory signal. So how does our brain "interprets" the difference between odours? That would be very interesting if we can find out.
Like you said, there are different types of gpcrs...maybe the speed or frequency in which they fire or rhythm or something that helps the brain to interpret? And of course interconnection with other brain areas.
Different receptors project to different glomeruli, so there is topographic mapping of different odors in the brain. There is also a theory about the timing of firing of different neurons but it's not yet proven.
@@Alilamedicalmedia 👍 Very interesting, thank you for this video and reply.
in accident my nose and forehead damaged recently some surgey's corrected my nose and forehead but smell is not coming how to recovery my smell??
Did your smell came back?
Well explained.why smell sense become poor in some people facing rhinitis
What can help with all the rancid rotten smells it's been 10 weeks and I can only eat toast jelly or Ritz crackers help me who can help reset it for me
I hope that you are okay now but you need to pay a visit to your GP and then you could be referred to a psychiatrist
@@kerolusmourad5795 I'm fine now
can we get the references please !
No thx, i feel like bob was exaggerating, i cant believe his ex girlfriend destroyed his paintings. What a shame. She was a sweet girl, idk why she did that. Hes a great artist, and when he dated her she always supported him, i cant get it. Whyd she destroy his art if she was the one that supported him throughout his career.
what is the connection between covid that makes the olfactory neurons not fire off, thus making taste/smell no active?
This seems to be not thoroughly investigated yet and is a subject of active research.
Tq
🦋🦋🦋🦋🦋🦋 beautiful
😮❤
That's what I am finding 👍
Can you help me with this sir /ma'am olfactory adaptation.. obtain some absorbent cotton and two of the following oil (oil of wintergreen peppermint, cloves. press one nostril or stuffs it with cotton. hold a bottle of oil under open nostril on exhale through mouth (for olfactory adaptation to occur) record the time. repeat the procedure with the other nostril recorded time immediately test the nostril that has just experienced olfactory adaptation with other oil record the result
This video taught me something... but remember if you smell a fart tiny poop pieces got up your nose.
😂😂
I m suffering from anosmiya last ten years, please anyone can help me🙏🙏🙏
Lako dilo ki dhadkan
Well
Head trauma caused me anosmia, it's about 2 years after the accident 😢
Thank you for this work, it is totally helpful in Police work always, including the war against drugs, & detecting illegal drugs.
And T.H.C (weed)?
It's very weird..I keep smelling toothpaste.
....and!....
We all know how it works but no one wants to tell us how the airborne molecules form…
I Love Jonna Napire 💜💚❤
March 23, 2024
Have people that have no sense of smell been studied to understand why they have no sense of smell?
Is it dmg of some sort? Is it like a birth defect issue?
As far as I can remember I've never been able to smell.
Vand re 😂😂😂😂
How do people discover this shit its crazy
Eucalyptus and rosemary have a floral scent now but cant smell farts or fire. This shit is confusing and annoying
How are u feeling now ? Did ur smell came back completely