But actually, for this type of cell, the outer hair cell, they don't have so much afferent fibers connected. Many uses their efferent. There is actually this one, this process actually is those neurons from the brain stem [FOREIGN] so the information actually is coming down from the brain to control these cells okay? Quite important here, the distinction. Later we will talk about actually how these two type of cells function. Here, the picture of the two type of cells. This one called outer hair cell, okay. I think you should partition when you make a section of the cochlea and then, you have a three layer to the some type. Three roll of the outer hair cell but, only one row of the in outer hair cell make it is so it's quite interesting why you arrange it this way, right. Okay, so we talk about actually this, actually hair cells locate in the cochlea. The cochlea is like a snail, like a [FOREIGN] so if you open this cochlea, what you can see. It's like this, you open this one, and then you can make it straight, like this, right? So on this cochlear and then there is a special membrane called the basilar membrane. This membrane can actually vibrate and then this membrane actually sit in the middle there. They're very different. This one this grey band is a basilar membrane. And on the top and on the bottom actually they are a lot of [FOREIGN] so take a look here. The sound actually propagates by those tiny bones. [FOREIGN] Okay? When this one look at this membrane not [FOREIGN] okay. [FOREIGN] Basically a membrane that you. [FOREIGN] Well this is base, the base of the membrane vibrate, because it's a hair cell just to sit on top of this membrane. Okay? So, the hair cell will also be kind of a move up and down. So, the hair cell it's a hail bongo we showed actually just a few, maybe two slides ago that there is another membrane actually on top of the hair bundle. So when this basically membrane actually move up and down and then you will cost the shift force [FOREIGN] hell bundle another membrane between that membrane and the hell bundle, okay? So that way the cost are hair cell to receive the mechanical force okay. There is another property of this basilar membrane, okay? This one. Okay you can take a look. It's quite strange all right, so this site, this cochlea, we call this site actually this is a base, okay. When you opened, and then the then we cut apex. And then this site, of course actually looks much larger, right. But then actually this basilar membrane at a disc location is quite actually narrow. It's orbital, okay? So this side is much wider, this side. So this basilar membrane, so at this region will be more region and is far wider. And it's in this region they will be. Sound that you propagate along this basic membrane. The frequency of properties will be different. That is actually the high frequency sound like this region because this region is much smaller and this region will be more sensitive to the low frequency. Okay? Or you can take a look. This is actually the frequency distribution along this basic membrane. So high frequency at the base. Low frequency detection or low frequency vibration mainly happen on this at the top, at the tip of this cochlea, okay. We know actually the sound, what's the features of the sound, when we detect a sound, what kind of thing we are particularly interested in, the features. The sound, one is frequency, right? And the second is the strength, the intensity, its loudness. And the third one is location. Where is the sound coming from. The frequency right now, as we can see from this slide, the frequency is already encoded with this basilar membrane, the properties, okay? [FOREIGN] Took a base from. So if we locate on top of this region. The base region. That it means those hair cells we mostly receive the high frequency stimulation right? And then of course at this region there is low frequencies. [FOREIGN] Okay, [FOREIGN]
