Phototransduction and photoreceptors | Physiology of vision | Special senses mbbs 1st year lecture

Physiology lecture on special senses physiology : vision physiology details the phototransduction mechanism in retina i.e how photoreceptors i.e rods and cones convert the energy of photons to light energy. Then it also differentiates rods and cones and how they differ in the phototransduction mechanism and mechanism of adaptation.
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The phototransduction occurs at rods and cones outer segment when a photon strikes the photopigment rhodopsin/photopsin. This causes activation of enzyme phosphodiesterase and hence decreases the concentration of cGMP in the photoreceptors. This is the only step where the photon is involved in the process of phototransduction. The decrease in cGMP closes sodium channels and causes hyperpolarization of the photoreceptors.
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00:00 Introduction to phototransduction
01:14 Structure of rods and cones
01:41 Phototransduction (dark)
02:40 Phototransduction (light)
05:05 Absorption spectrum of photoreceptors
06:38 Difference in phototransduction in rods and cones
08:37 Phototransduction and light intensity
09:10 Light adaptation
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[@ilakianperunthagaimk8173]

Superb video...

[@PhysiologyOpen]

Thanks 😊

[@ashaevangeline2316]

No words to thank you ma'am....You made it very easy....Lots of respect to you from tamilnadu ♥️😊

[@PhysiologyOpen]

Thank you so much. Best wishes

[@user-kh7il8zr9k]

Many informations✨💥 Thankyu mam

[@PhysiologyOpen]

😊❤️

[@aadityasinha6961]

Beautifully explained maaam !!

[@PhysiologyOpen]

Thankyou

[@alisha7739]

Mam could you explain on and off biopolar cell am not understanding what is the function of it and also when hyperpolarization occur so we can see or not

[@PhysiologyOpen]

Ok will work on that soon

[@kusumapriyagonuguntla4591]

Mam can rods respond if the light is dim (less intensity) and not within their range of wavelength for example we enter a room with only red light but very less intensity

[@PhysiologyOpen]

Yes...actually in bright light they get fully bleached. In red light, bleaching is there but not up to that intensity. That’s why red light helps in dark adaptation because the rods are not that much bleached

[@josetrujillo738]

This was a very nice explanation

[@PhysiologyOpen]

Thank you

[@drshaunmurphy9250]

Great explanation mam❣❣

[@PhysiologyOpen]

Thanks

[@tauqirahmed1806]

maam how is hyperpolarization sending signals to brain? shouldnt depolarization tranmit signals

[@PhysiologyOpen]

All cells of retina except ganglion cells produce only graded potentials. Only ganglion cells generate action potential. There is some baseline activity in ganglion cells …depending on the signal from other retinal cells, the action potential frequency in ganglion cells either increases or decreases

[@aaqil8344]

Ma’am can you please explain the difference between electrotonic conduction and conduction via action potentials. How does it change our perception and interpretation of various stimuli? Thank you ma’am

[@PhysiologyOpen]

electrotonic conduction is a graded cgange in potential. graded potential basically increases with increase in the strength of the stimulus. If graded potential change reaches threshold then only action potential is generated. when action potentials reach CNS, we percieve the stimulus. So if graded potential change doesnt reach threshold, we dont percive stimulus...Also, graded potential determines also the no. of action potentials generated...which determines how much strength of stimulus we percieve..Please watch this for more: kzbin.info/www/bejne/jZauenmHoa1naZo

[@aaqil8344]

@@PhysiologyOpen thank you ma’am!

[@ankushbadgal7379]

amazing❤❤

[@PhysiologyOpen]

Loved it that you liked it

[@dnyaneshwarjadhav1813]

is there any particular sequence in which we should watch these videos

[@PhysiologyOpen]

Watch playlist in sequence for each system

[@joebarbhuiya4049]

Thank you so much maam...

[@PhysiologyOpen]

You are most welcome

[@LaxmiLaxmi-vd6vu]

Awesome🖤

[@PhysiologyOpen]

Thank you

[@ilakianperunthagaimk8173]

Suberb video.....

[@PhysiologyOpen]

Thanks a lot

[@SumitVerma-kv9gg]

Ma'am can you make a complete video on eye..... Must needed 🙏

[@PhysiologyOpen]

Wil try

[@Tasneemkwel]

wow .

[@PhysiologyOpen]

😊

[@abhinandanjangid5453]

Underrated..

[@PhysiologyOpen]

yeah...I knowww

[@shaikmateen6041]

Mam i have a doubt regarding intracellular calcium you mentioned that decrease intracellular calcium helps in light adaptation by increasing cgmp levels for which ligand gated sodium channels have higher affinity but if we take reverse function of calcium increase should have inhibitory action on enzyme guanyle cyclase thus reducing cgmp leading to depolarization as in phototransduction how is it possible???if it is so no photoreceptor will maintain that depolarized state then ???

[@PhysiologyOpen]

What reverse function…sorry I didn’t get your question much…calcium has different effects in different cells..in rods it increases cgmp…so I don’t get next part of you question

[@shaikmateen6041]

@@PhysiologyOpen mam you mentioned regarding the light adaptation part where you told that decrease in intracellular calcium will result in stimulation of enzyme guanyayl cyclase which increase CGMP via which the sodium ligated channels have high affinity for it thus leading to decreased absorption of photon...so,now mam my doubt is decrease in calcium should have inhibitory affect on that enzyme so the photoreceptor should undergo into a state of hyperpolarisation even without photon absorption how is it possible mam??

[@shaikmateen6041]

And I listened to it repeatedly you mentioned saying increase in calcium have inhibitory effect on enzyme gunayayl cyclase

[@vaishnavdas4450]

HARE Krishna dandvat pranam thankyou so much mam Mam please pray for me my exams are coming

[@vaishnavdas4450]

Please bless me

[@PhysiologyOpen]

May you do best in your exams. May lord be with you

[@moizjawed5307]

best

[@PhysiologyOpen]

Thank you