Photoreceptors (rods vs cones) | Processing the Environment | MCAT | Khan Academy

In this video, I explore the similarities and differences between rods and cones. By Ronald Sahyouni. Created by Ronald Sahyouni.
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[@gavinh2614]

Please note that the discs inside a rod are NOT called optic discs. The optic disc is equivalent to the blind spot since this is where the optic nerve is exiting the retina. It's important to know that there are no rods or cones in the optic disc as well

[@rawdonwaller]

as someone else commented: action potentials only arise from the ganglion cells.

[@Juhcamposc]

What a great explanation! Thank you

[@christiandorcaskisely3946]

Thanks a lot ! Great video ! Well illustrated

[@johntepp]

rods and cones dont fire APs, just transmit graded potentials.

[@AxxLAfriku]

hi

[@Pebblebrook]

@@AxxLAfriku hi? 😭

[@zuhraaziz8225]

I don't know if Khan academy has already done this or not, but you should make a video on the visual pathways (Geniculostriate, tectopulvoinar, and Retinohypothalamic). It is a bit hard to understand just by reading about them from the textbook.

[@edwinrelf8454]

Rods and cones do not fire action potentials

[@c00perz1]

Can you explain further, how do they convert this iforrmation

[@iamjoshua]

Jack Coupland They are actually always "on", continuously releasing the neurotransmitter glutamate to attached bipolar cells. They stop doing so when they become stimulated by photons. So this video is incorrect as Edwin points out. en.wikipedia.org/wiki/Photoreceptor_cell

[@byronstrohm3887]

Correct, they are constantly generating excitatory graded potentials in the absence of light, causing the release of inhibitory NT in the synapse between them and the bipolar cells they communicate with. In the presence of light, these graded potentials in the photoreceptors stop which stops the release of the inhibitory NT at the synapse. This causes the postsynaptic bipolar cell to depolarize. They release excitatory NT in the synapse between them (bipolar cell) and the Ganglion cell they are hooked up to. Ganglion cells then depolarize which turn into the optic nerve and an action potentials makes its way down the optic tract. Life is truly amazing

[@Ispeaktruth18]

Byron Strohm if you know all that why are you watching this video?

[@francescakhamisa9757]

true. only ganglion cells generate action potentials!

[@DannyMercer1993]

That was excellent :)

[@savannahtallino8534]

Looks like the video (at the end) is also incorrect about dark vs. light adaptation (they got it backward). Bummer. Was going to use this video to help my students but there's too many conflicting details and I don't want to confuse them.

[@attractive5858]

this video was helped me! thanks a lot

[@krugertiaantk]

great!!!

[@UHFStation1]

Is it the shape of the cones that give us fine detail, and do certain retina diseases that damage fine detail alter the cones' shape?

[@cosycheung]

Thanks for sharing

[@zachklepper]

What is the method to determine how many rods/cones there are?

[@camilacruz1937]

Great explanation!Thank You!

[@umeshsingh355]

Hi

[@LegiRGomes]

Thanks for your explanation it really helped me a lot

[@frosty5090]

Rigel H. R. Gome

[@albertesquivel6545]

You shouldn't use the terminology optic disks because that also refers to the optic nerve.

[@b.bharathkumar7332]

worthy till now.....

[@varunjoshi8251]

Thank you :-)

[@orchidsrain]

this really helped ! Thankyou

[@frosty5090]

Gargi Prabha Hi

[@adamjzimmer]

I spent a solid hour of searching to find this exact explanation, and then I read the comments and key parts are wrong?? If this is not accurate you should delete or edit the video. You're misinforming people. If you have other videos, you should fact check them and make sure you're correct when stating scientific facts.

[@craerae]

Just correct what's the mistake

[@Sora-ce1zx]

I think this is the reason why the comment section exists. Khan academy are not experts and not well paid. And it’s free to anybody. In a lot of Khan academy videos, mistakes are here and there, but we can’t blame them. Instead, we should just point it out in the comment section and support them.

[@meenasalve9146]

Thank you so much

[@parakhmody1413]

"Rods and cones do not fire action potentials" ---Edwin Relf How do you respond to that? Also, isn't the slow recovery time due to pupil dilation/contraction? What I'm getting at is that isn't there a time limit(refractory period), which, once elapsed, any neuron will necessarily fire an action potential, regardless of what kind of neuron it is, given the right conditions(more permeability for Na+ than K+)?

[@harox77]

thank you so much

[@mcmuffin1220]

What is the difference between photopsin and iodopsin? My book says that cones contain iodopsin. Are they just two words for the same thing?

[@sugarsugar4410]

+Mac Muffin photopsin is a more specified kind of iodopsin !

[@passer-by8732]

merci

[@paradiseentertainment166]

What are the 3 photopigments in cone ?

[@PhysiologyOpen]

In rods the discs are not membrane-bound, they are free-floating..In cones, they are membrane-bound. Also as many people mentioned, rods and cones don't fire action potential

[@mintmonkey1017]

Please could I have a list of keywords for the parts?!📚

[@_dahlia.may_]

Fovea Retina Optic discs Rods Cones

[@abiabisiscutty9221]

Tq

[@Hellohellonamehere]

Only ganglion cells fire, correct?

[@MadTwatter]

*Re-ina*

[@keegancan]

So, if we run inside after playing sports to get a cup of water maybe our eyes adjust better to lighting that changes just a little bit compared to going to a lighted room to a darker room?

[@simranyadav9275]

Ya most probably because even the iris needs to adjust it's size according to the light intensity.

[@iwillbeback8686]

3:13 function

[@barbaricrawr4190]

Wouldn't the cells be called neurons and NOT nerves? Nerves are bundles of axons...

[@khal2652]

Cones and rods are neurones not nerves right???

[@perrymiddaugh8614]

Taped on this and through it was the Blue Man Group song😂

[@bellpepper3166]

You can learn this from blue man group.

[@frosty5090]

Dubbers Voicemai has

[@zamzam515]

it’s cone shaped: draws a triangle

[@youreanonshareer]

zamzam are you dumb...?

[@Distruct10]

what do you think a cone looks like from the side

[@zamzam515]

youreanonshareer I was going through it that time period.

[@zamzam515]

SugarNaught pls I was just a dumb sophomore let me live

[@Distruct10]

@@zamzam515 lol its ok glad you got through it

[@ghkageyama]

Rods and Cones do not generate action potentials.

[@KiranSingh-es2ot]

Why do you keep saying “optic discs”? Optic discs actually have a very defined meaning in optic terminology. Optic discs refer to the optic nerve head (ONH). You’re misleading people by calling the photoreceptor discs of rods “optic discs”. It’ll get confusing for people when textbooks refer to the optic discs for other explanations not related to photoreceptors

[@BostonPower]

ABRUPT ENDING MUCH? LOL

[@vechniyyt5778]

МАШУКА МАШУКА Т

[@9-volt247]

Huh? I can't understand that language! It may be Russian that you're speaking. I only speak English and Spanish.

[@holyspecs]

Poda

[@myhouseB]

this..isnt...Khan

[@tachtoucho]

everything he said is false !

[@milindpathak-here]

And many say , God doesn't exist !!

[@9-volt247]

GOD DOES EXIST!! WHERE IS YOUR COMMON SENSE?! 🤬🤬🤬

[@moongirl6128]

What a great explanation! Thank you