1.2.4 Phototransduction-III

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From the course by Peking University

Advanced Neurobiology II

53 ratings

Peking University

Advanced Neurobiology II

53 ratings

Hello everyone! Welcome to advanced neurobiology! Neuroscience is a wonderful branch of science on how our brain perceives the external world, how our brain thinks, how our brain responds to the outside of the world, and how during disease or aging the neuronal connections deteriorate. We’re trying to understand the molecular, cellular nature and the circuitry arrangement of how nervous system works. Through this course, you'll have a comprehensive understanding of basic neuroanatomy, electral signal transduction, movement and several diseases in the nervous system. This advanced neurobiology course is composed of 2 parts (Advanced neurobiology I and Advanced neurobiology Il). They are related to each other on the content but not on scoring or certification, so you can choose either or both. It’s recommended that you take them sequentially and it’s great if you’ve already acquired a basic understanding of biology. Thank you for joining us!

From the lesson

Perception: Vision

1.2.1 Review20:49

1.2.2 Phototransduction-I15:33

1.2.3 Phototransduction-II10:54

1.2.4 Phototransduction-III8:53

1.2.5 Color vision-I7:48

1.2.6 Color vision-II20:08

1.2.7 Signal processing of the retina18:40

Meet the Instructors

Chenjian Li
Professor
School of Life Sciences
Donggen Luo
Research Fellow
School of Life Sciences
Yan Zhang
Professor
School of Life Sciences, Peking University

Yeah one photon for one photoreceptor, right.

That's actually amazing.

And then can you really see that one photon the signal for

one cell because measured that.

When your perceive the light you just

need one photon to activate the one receptive neuron and

then of course happen maybe five to six simultaneously different neuron, right.

But in any case the mediation it's one cell

you need to respond to one single photon.

And with this technique they found this Single-Photon Response from the one cell.

Look at that here, this is a picture showing the photo recording.

Again, such impact the recording [FOREIGN].

And then this is the Single-Photon Response.

So this actually is continuous recording, okay.

It's just from here, connect here, for the display to show you, the brick,

easy for viewing, for the display.

And then at different times, you see it equals a interval.

Give it a light flash.

This light stimulation actually makes

the intensity quite low.

And average may be just 0.5 photons per flash.

And then what you can see is sometimes there's actually no response.

Sometimes maybe it is small bumps.

Sometimes larger bumps.

This larger one you can easily think it's two, a small overlap.

This is the quantum response.

Look at here.

The small one is the Single-Photon Response.

The larger one is the two fold photon response.

How you can achieve such like 0.5

photons per flash stimulation.

We know the light the minimum unit is a photon

you cannot just divide the photon into half.

[FOREIGN] >> Do you think do you know someone

with a question.

>> The question is actually how can you,

given the light intensity,

only have 0.5 photons per flash.

[FOREIGN]

>> [INAUDIBLE]

>> What?

>> [INAUDIBLE] >> A mirror.

>> [INAUDIBLE].

>> [FOREIGN]

[FOREIGN]

This

kind

of

fluctuation.

[FOREIGN] response [FOREIGN].

Says vesicle transmitter release, right?

Is a counter release, right?

[FOREIGN]

Distribution.

[FOREIGN]

distribution [FOREIGN].

If you collect all this data like a mixture of this plot.

This is actually OK.

No response how many times happens, right?

And here you can count, of course, this is maybe not enough.

You have many, many more recordings.

And you make this plot.

So at one picoampere here, then you count how many times happen.

And then of course then you have two picoampere.

And from this you can fit by the [INAUDIBLE] process exactly.

That means actually indeed this is the single photon response, okay?

Just like here.

This is a single, this is actually

the response to two photons.

[FOREIGN].

If you have a partial distribution,

you know the average lambda of the events, the lambda.

Just a partial [FOREIGN] function [FOREIGN] lambda.

[FOREIGN] Okay?

Exactly [FOREIGN] describe the [INAUDIBLE] distribution.

Okay, so we talk about actually this single photon response.

This only happens in the receptor.

[FOREIGN] photo receptor.

Because, they [INAUDIBLE] photo receptor actually is very sensitive and

then responsible for the [INAUDIBLE] edition.

[FOREIGN]

Okay.

For the cone [FOREIGN].

No, this is a different scenario.

[FOREIGN].

They don't have this single photon response.

[FOREIGN]

So we still have the, rely on the cone for

the receptor quite heavily, okay?

So because actually in the daytime you want to see the color.

You want to see the motion, this all coming from the cone,

photo receptors, okay?

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