Olfaction - structure and function | Processing the Environment | MCAT | Khan Academy

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[@austinfrisbey5199]

Minor correction, but the G-protein doesn't bind to any ion channels. It binds to and activates Adenylate cyclase which converts ATP to cAMP. The cAMP then binds to cAMP-gated ion channels on the cell and causes them to open, allowing Na+ and Ca2+ to enter the cell. Na+ causes depolarization and Ca2+ causes Cl- channels to open. This causes Cl- to flow out of the cell, increasing depolarization and eventually triggering an action potential.

[@niiinjaaa3241]

Yep i noticed that too. There is also activation of the PLC (phospholipase) which produce IP3 (bind to Endoplasmique Reticulum Ca2+ channel, and plasmique membrane Ca2+ channel) et DAG (recruit PKC, which also can trigger the opening of cation channel)

[@trentwoodruff4308]

There is a G-protein signal cascade, namely, Gs activation. 1. The odorant will bind to GPCR. 2. Conformational change of GPCR causing separation of G-alpha and G-beta-gamma. 3. Now, the G-alpha will become activated with the help of GDP to GTP. 4. G-alpha will bind to Adenylyl Cyclase and cause cAMP production. 5. cAMP allows for cations, Na+ and Ca2+ to depolarize the cell.

[@trentwoodruff4308]

Cl- influx into the cell will cause hyper-polarization, not leading to an action potential. Thus if they came in through channels, this would not cause activation.

[@trentwoodruff4308]

No. This system uses the Gs pathway. You're thinking about the Gq pathway, which is also excitatory but not used in olfaction!

[@calimorales9880]

Ummm.... what?

[@AudreyVictoria]

Sensation and perception final exam in exactly one hour. Thank you for this!

[@sharieshok2627]

Audrey Victoria i

[@jayjansen9086]

Same

[@user-zb3pm8lh1p]

did you pass? (if you can remember lol)

[@nabeel1119]

@@user-zb3pm8lh1p do we still remember

[@lesslyjimenez3757]

Things I learned from this video: 1. Every olfactory sensory neuron is sensitive to cells that cause it to be sensitive to it and it causes synapses which then gets sent to the mitral cell which sends it to the brain. 2. Not all olfactory sensory cells synapse to the same they go to different mitral cells.

[@inteend]

got exam tomorrow and you saved my butt with your videos! ten times better than any lecture. thanks mate

[@sci_of_the_era7482]

thanks i want to learn english plz suggest me

[@Rjh_-mj9tl]

In this video, I learned that the cribriform plate is the bone that separates the olfactory epithelium from the brain. This is also the site at which the olfactory bulb sits and interprets the information from the dendrites in the olfactory epithelium. The cribriform plate also has holes that allow for the neurons to travel from the olfactory spilt to the olfactory bulb. I also learned that each glomerulus is the place where neurons for one specific type of molecule or smell meet up to send signals through the mitral cells. I learned that mitral cells are also called tufted cells. Lastly, I learned that the molecules responsible for smell bind to a G-protein coupled receptor, thereby triggering an action potential.

[@fnulnu13]

Thank you for the video, just FYI there is a type-o here. The correct spelling is "cribriform" plate; in this video the r is left out after the b.

[@dylansmd5072]

Agree with u... Threr should be "r" in between b and i..

[@Lucky_25]

That's exactly what i was going to say :)

[@krista1722]

For the MCAT do we have to know the names of the specifics such as the glomerulus or the mitral/tufted cells? Exactly how specific do you think the MCAT will be?

[@emeka3033]

wing it

[@byebye6828]

@@emeka3033 lol

[@suhaibsofi4154]

Big fan sir big fan ❤️

[@LSI_MGA]

Our lecturer said that the receptor for the smell does not fire action potentials, but it transfer the information to the ganglion via neurotransmitters due to receptor potential (which is different because it is continues - it does not have threshold etc). can you please elaborate on that?

[@lumbiwemwanangono8954]

It actually does fire action potential cause the receptors are on the neuron (cranial nerve I)

[@mohsinkashif3674]

you didnt explain its pathway to primary and secondary olfactory cortex

[@TheMajorshroom]

agreed, it would've been useful if you went on with the pathway into the higher processing centres in the brain, but apart from that useful thanks :)

[@mikoaryayenijad]

I am her becasue covid took my smell and tast 😢

[@plymouthlad38]

Kallmann syndrome is a congenital hormonal condition that causes absent or not fully completed puberty in addition to anosmia. The migration of the olfactory neurones through the cribriform plate into where the olfactory bulb should form is blocked. GnRH releasing neurones which should migrate into the hypothalamus during early development follow the same route and their progress is also blocked. This prevents the hypothalamus from being able to release GnRH which prevents puberty and the reproductive cycle occurring in both males and females.

[@brianpiper848]

The olfactory epithelium is 1 to 2 square cm so pretty small. The first 5 min showed it much larger but we get the general idea.

[@rushabhsheregar]

thanks for the video,really helpful for last min refrence keep on adding such helpful lessons

[@cipher0006]

Is an action potential more or less binary code?

[@SixTough]

sounds like you are implying 9 to 10 million different receptors solely in the nose. this is not the case

[@humnahabib6418]

Sir I closed my nose but the taste was same

[@budoor-km7jk]

Thank youuuuu

[@hippiegolucky8257]

You sound like blameitonjorge

[@katykh1800]

bravooo

[@rebeccabridges5227]

khan academy never lets me down.

[@arocks1234567]

Brain olfactory bulb cribiform plate, and olfactory bulb sensory projections in olfactory epithelium of mouth Benzene goes into nose, binds to olfactory nerve endings, Cribiform bulb has spaces that allow olfactory nerve to take signals to olfactory bulbs Each receptor for each scent Cascade of events till it reaches olfactory bulb, whole bunch of cells fire at one location called glomerulus- destination site for all cells sensitive to same molecules Glomerulus synapses and mitral/ tufted cells Blue cell will synapse at another glomerulus. Tufted cells go to brain Scents used g protein coupled receptors to cause cascade of events All similar places meet at their own glomerulus on the bulb and they have their own It has a different mitral/tufted cell that will go to brain

[@hmhross]

these videos help a lot for people in medical school. please keep making them!!

[@hamodale]

king

[@curiousminds8948]

Great work 👍👍👍👍

[@katna1799]

(Theoretical question beyond the scope of the MCAT) Is it possible for a neuron for a specific smell to synapse at a different glomerulus site? Meaning that a smell such as a fart could smell like a sweet rose? But then again, I guess each smell has hundreds of different neurons, so for the entire smell to be converted I guess they would all have to synapse at a different glomerulus site. Even if it is not possible for neurons to synapse at a different glomerulus site, I guess maybe it could be possible for receptors to become sensitive to a molecule they weren’t designed for, eliciting the same response as described above?

[@mohamedaslam9190]

you are saying that our nose has a epithelial cells for each oduor then there are more than trillion odours.. so our nose has that many cells??

[@calimorales9880]

Yes

[@flerma223]

My brain hurts:(

[@susiesuuu3586]

It has puzzled me for a long time! Thanks a lot!!!

[@queenqadraofficial9025]

How can this dysfunction be treated

[@dannysaravska3036]

Nice explanation, well done! I suffer from a hightened sense of smell. Any thoughts of how can I alleviate this? Thank you

[@nicholaspeterson6137]

Protein*

[@birukwondi3889]

❤❤

[@mohamedaslam9190]

how does an g protein convert into action potential?

[@ganeshkrishnamurthy6508]

Good Explanation. Helped me. Thanks

[@kackieedgcumbe8477]

thank you

[@aarjomandnia9711]

Great, just wish it went into even more detail about the physiology

[@Ravenwest19]

one cell has only one type of receptors?

[@Awesomestevie100]

Awesome video that hit on a bunch of key vocab on my next test. Thanks!

[@bhumishahyoyo]

Thank u....its vry informing nd i hope i ll do good in my cls

[@sujikim6726]

So helpful. Thanks!!

[@courtneyadavis]

Thanks for the video, I've been watching lots of these and they are great!

[@dylansmd5072]

Thanks a lot man... Good luck

[@miss0noodle]

cribiform=cribriform

[@JimNagle87]

Mmmm... Strawberries :3

[@sarahclairview]

thank you

[@boo766]

Thanks a lot !!

[@Nikiki156]

So neat. thank u

[@安娜-b9g]

Thank you. And do you want to say"cribriform plate", but not "cribiform plate"?

[@suchasasong]

Thank you so much!!

[@aedanmcmahon1951]

How does the receptor system reset after a molecule has attached itself to the receptor? Why do we stop smelling the odour? The g-protein detaches, so how does the GPCR part reset? Ps great video, good clear introduction

[@ryarau9008]

Part of the G protein which detached from the GPCR did so because a GDP molecule it was bound to was swapped out for a GTP molecule. Eventually, the free G protein subunit hydrolyzes the GTP it’s attached to, causing reassociation with the other subunits still bound to the GPCR.

[@IWork4Dessert]

I can't watch this because of the sheer number of times the word "actually" is said