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2.2.3 Sound transduction-III
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来自 Peking University 的课程
Advanced Neurobiology II
59 个评分
从本节课中
Perception: Auditory
与讲师见面
Chenjian LiProfessor
School of Life Sciences
Donggen LuoResearch Fellow
School of Life Sciences
Yan ZhangProfessor
School of Life Sciences, Peking University
Let's take a look.
How the hair cell to detect the mechanical force.
So, if you isolate a hair cell, it looks like this.
This is the isolated cell.
This is, of course, this is a cell body, right?
And then, what's this?
This is the hair bundle.
Hair bundle is the part to receive the sound stimulation, okay?
So, you can do a function essay using a [INAUDIBLE] recording.
Then you can record from the single cell, so
their pipette to record the electric signal.
And then you use another pipette to stimulate this
hair bundle to move up and down, okay?
Then you will see this is a signal.
So, this one that uses a stimulation, okay,
so, this simulation is the micrometer,
that means you have a pipette to move the cell
to maybe forward by one micro meter and
0.5 micrometer and to 1 micrometer.
And also, you can put another direction of the hair bundle, okay?
So, any direction, you can do with a simulation.
Take a look at the response.
This is the response of the sale.
Okay.
In the resting state, not much happened to the sale.
But when you have a stimulation of the hair bundle.
The cell will give a immediate response.
You can take a look here.
This is a response to a small stimulation, and
then to larger stimulation and again, much larger.
And then what happens here, quite interesting, okay.
What's the feature of this response?
Can you describe?
[INAUDIBLE] So, take a look at this response, okay?
So immediately, I guess it's very obvious, some features of this response.
So, what kind of important features you are looking,
you can seeing about this response?
>> Okay, that's good.
So you mean.
You mean, this wrist bones cannot stimulation, will get smaller.
Okay, good.
This is called adaptation, okay?
And that's the only one?
>> After the stimuli, you have also the [INAUDIBLE].
>> Okay. That's the second yep.
The [INAUDIBLE] response right?
>> [INAUDIBLE] >> Direction.
>> [INAUDIBLE] >> Good, okay.
So, if you give approach and that's a direction, right?
So, the response would go to another direction, okay?
This is the certain features.
Anymore?
>> [INAUDIBLE]
>> [INAUDIBLE]
>> Yes.
>> [INAUDIBLE] >> Okay, good.
You mean the cell can be saturated, right?
That's good, okay.
Yes, these are all important features.
Good, any more?
So, the crew is actually, think about actually last hand.
I show you the photo response to light.
You give light stimulation, the photoreceptor,
will also give Response, right?
That response compared with this response, they kind of very-
>> [INAUDIBLE]
>> Okay, good.
That one is a hyperpolarization.
Yes, outward, going up, right?
This is [INAUDIBLE], good.
This is a very important difference between this hair cell and
the photoreceptor.
Another key feature, real difference between these two?
We emphasized it actually quite a lot during
the discussion about the photo response.
>> [INAUDIBLE] Photo receptors [INAUDIBLE].
>> Yes, yes.
>> [INAUDIBLE] >> Yeah, yeah.
[LAUGH] That's actually corresponding to hyperozation and depolarization,
we already talked about this feature.
It just repeated the same feature.
So, in the photo receptor,
we talk about actually there is a lot for biochemical reaction.
So depth, right?
And then, from there, when you have a slight stimulation,
the response does not appear.
And actually, after the delay, then the response appear.
Sometimes, it may be, what, about one second, right?
For some species.
And take a look here.
This is the stimulation.
Almost immediately the response appear.
Right?
So, this is actually a key feature of hair cell,
that means the cell respond to the stimulation without too much delay.
So, if you.
Compare the stimulation, and this is raising over the response,
that delay is waiting maybe 10 to 100 micrometers, microsecond.
There should be a high pressure, a high hung up into it.
For this, then there was a thing about okay,
how this transduction happens with this hair cell take a short time?
So apparently, so, during this process of the signaling,
the second messenger does not involve.
Because second messenger,
you would take a lot of time to accumulate from one step to another step.
So for this one, you can, and be to think about it is maybe, okay.
So, there is a one channel sitting on the membrane.
And the data force coming directly open to the channel.
Just so they got gate, you just open.
And then the Ion can influx into the cell make it depolarization.
Okay.
So, indeed, this is actually the hair bundle.
Okay. So we take a look at,
this is a hair bundle.
So, the hair bundle
actually is mainly meaning
[INAUDIBLE] [FOREIGN].
Quite a lot.
[FOREIGN] If you have
a M structure.
[FOREIGN] Okay.
Well, this is what
you can see founds that
Structure of [FOREIGN]
a spring, right?
[FOREIGN] This structure
is called the tip link.
Okay, tip link is from again,
is a link that the shorter one to the longer one.
Okay. [FOREIGN]
So,
you can imagine if we have our channel.
[FOREIGN] Channel sit at this region.
And the channel, the gate [FOREIGN]
is pulled by this tip link.
So when your hair bundle
move in that direction,
[FOREIGN] okay?
[FOREIGN] Okay?
Here, there is
the real model at the resting state.
So, there was a channel up to this region.
And then there was, the channel, of course, has the gate.
You can [FOREIGN].
Our channel unit open has a gate there.
And this gate connect to the tip link, okay?
So, if you have a mechanical force, the hair bundle in that direction.
You see, this one will pull the gate open and
is a cell immediately give the response.
So, okay, this is hypothesis for the mechanical transduction.
How can you approve?
Your experiments demonstrate this isn't true.
>> [INAUDIBLE] >> Good.
So, you may be, in some special way,
to break the link and see what happen right, okay?
