[MUSIC] Okay, so what we looked at in the last segment was how an individual end organ, and end organ means either a semicircular canal or orniconial mass. How the hair cells work in in one of those. Well, in fact, our head is, is, is one head so there are pairs that are going to get exactly the same stimulus. And they're going to work together so let's figure out what those pairs are. We're going to look at the first at the semicircular canals and there are three on each side. We talked about dividing the planes of rotation into three. And they exist on both sides. Well, if there is a rotation in this yaw plane. This is the yaw plane saying no. That's yaw. I'm rotating in the yaw plane. Well, it will affect this canal and this canal. So whatever happens over here, the opposite is going to happen over here. They are a yoked pair, the horizontal canals. These are called the horizontal canals, and the left and right horizontal canal, they're yoked. So there is no normal circumstance under which they would get a anything but opposite inputs. So they couldn't both be excited, they couldn't both be inhibited and one can't be excited without the other one being excited. So they have, they're yoked, they're always in opposition. Now, this, these, this interior canal and this posterior canal, they're also in the same plane. They're in this plane. So they're a yoked, they're a yoked pair, and similarly, this canal, the anterior canal on the left side and the posterior canal on the right side, they're yoked, so they're in the same plane. Alright, so. What? Look. What does that mean? Let's go over to the board for a second and I've just redrawn what I said on the tablet right here, but now let's take a side view and let's realize that there's a, there's also a a top-down orientation to this. So the anterior canal is here, posterior canal is here, horizontal canal is there, the hair cells are located here, here, and here. So lets think about what happens when somebody drinks a lot of alcohol. Well with alcohol intoxication, one of the things that happens is that the copula, which gets a blood supply of its own, it actually gets really light. It's light with alcohol, and it floats up. And so as a result of floating up, it can for instance stimulate the hair cells on, in the posterior canal. But not just the hair, the posterior canal but also say the anterior canal, and also the, the horizontal canal. And it can stimulate these hair cells in very non-normal patterns not just on the, on the, on one side but on both sides. And so all of a sudden what you're getting is this signal that makes absolutely no sense. It, there's no physical acceleration that could lead to this to this signal that you're getting from your vestibular end organs. So when would this happen through evolution? Well it would happen if you ate something that really messed with your blood chemistry. And so perhaps for that reason, this is the, the best reason I can give you, whether it's true or not I'm not positive. No one, no one really knows. These are hard arguments to prove or disprove. But the thought is that this, the, the mismatch, this completely non-physiological signal that you're getting in is simple interpreted as I ate something really bad, and now I need to go throw up. And so, beyond having the sense of vertigo, things are spinning, I'm spinning, the person with alcohol intoxication also feels nauseated. And this is called the sensory mismatch hypothesis. So the next segment we're going to talk about the yoked otoconial masses. [MUSIC]
