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Current time:0:00Total duration:8:40

Video transcript

let's say you have a man in a birthday cake and he's really excited to blow out the candles so he can eat the cake so he's gonna walk over let me just cut and paste him there you go he's walked over and in the moment before he walked over he was taking a nice deep breath and we call it inhaling he was inhaling air and then as he was next to the cake he was going to blow out the candle so in the moment that he blew out that's called exhaling now we know that inhaling requires a very powerful muscle called the diaphragm that's one of the most important muscles I want you to remember for inhaling and the other ones are these muscles that kind of are between the ribs and they're called the external external meaning closer to the outside of the body external intercostal meaning between introduced means between the ribs costal refers to the ribs so external intercostal muscles these two groups than the internal intercostals and the diaphragm these two groups are going to be very helpful in inhaling air there are others as well but these are the two you definitely want to remember and for exhaling they're actually important muscles as well we often think exhaling is just kind of a passive process but if you're blowing out candles and you really want to force air out there are actually some muscles here on the - here that I want you to remember are the abdominal muscles that really help us to generate a lot of pressure the abdominal muscles and then these and the other ones are called the internal intercostal muscles internal intercostal so internal comes up twice and these are actually a little bit closer to the inside of the body but they're also between the ribs so these two muscle groups are the most important ones for exhaling and just to make sure you get these two straight just look at these two words and you'll keep them separate so if things go as planned he's going to be able to take a nice deep breath inhale and then exhale a bunch of air and basically wipe out these candles and eat his cake so let's make a little bit of space and I want you to just keep in mind that this was all happening in a very voluntary way I mean he wanted to blow out those candles right but what about some involuntary things so let me drop some things that are involuntary things that actually seem to happen kind of on their own where the brain is just taking over and you don't really have to think about it and for the first example let me draw out the nose so this is the nose and a mouth and of course we have on the inside air coming in and we know the air is going to meet up between what's coming in through the nose and the mouth and let's say that you have some nerves and these nerves are right here and they're sensing some pollen or some you know sort of a irritant they're getting annoyed these nerves are going to be called mechanoreceptors mechanoreceptors they're they're very sensitive and they can actually pick up all sorts of things like dust so these mechanoreceptors if they sense that there's something there they're going to start sending a signal up to the brain now here's the cool part that's the signal going in the signal coming out of the brain will basically do a couple of things it'll lower the muscles here this is in the palate it'll lower the muscles there and it will raise the muscle known as the tongue so the tongue will come up a little bit and so now these two are going to work together to basically close off the mouth you can see how there's just a tiny little space here between the two where a little air could go back through but most of the air is going to have to go out this way so when you have a big exhalation meaning air coming back out if you're exhaling you're basically going to force air to go out through the nose and now you might be able to guess where this is all going to head to this is what we call sneezing right you say oh wow I just sneezed this is what your body did it basically kind of forced air through a forced exhalation to go out through the nose and basically wipe out anything that was irritating those mechanoreceptors so a sneeze is basically just an exhalation or a powerful exhale through the nose and now you can see how that works so pretty cool what's another example of an involuntary everything well let's say that you have your trachea here your trachea branches and you have of course some Meccano receptors there also here lining the trachea and if they get irritated again they're going to send a signal you guessed it they're going to send a signal to the brain so the brain is going to know hey something is bothering my trachea the mechanoreceptors have told me that now what's at the top of this trachea the trachea is going to have a little opening and that opening is going to be where the vocal cords are right you've got your vocal cords here on one side and on the other side there's a little opening I left and black fur for you to see where air is going to go through this is where air goes through usually and that's how we talk and sing right through the vocal cords so these white things are my vocal cords on both sides I've got two vocal cords right and a little gap between them and what's going to happen is that if the Meccano receptors are irritated then the brain is going to basically do a couple things it's going to push air out using of course remember those abdominal muscles and the internal intercostal muscles it's going to push air out and it's going to actually close off these vocal cords just for a a small moment is just going to close these off so what's going to happen is that pressure is going to build up you're going to get lots and lots of pressure I'm going to put it with an upward arrow and a P lots of pressure in the trachea right as you build up lots of pressure and then finally a split second later it's going to open the vocal cords back up and air is going to rush out right so what we call that when that happens is ack off we call that coughing you know that's the word we use but really what's happened we've had a very powerful exhalation using those muscles we talked about we've exhaled and then we've closed the vocal cords just temporarily so that you could build up even more pressure right because if you're pushing against something that's closed you can build up pressure and then pop it open and then have a almost like a mini explosion in your trachea and we call that mini explosion a cough a final example let me actually just get very quickly your stomach let's say your stomach has got little mechanoreceptors maybe right here and these mechanoreceptors are saying hey you know the stomach is pretty full and so they're sending messages up to the brain to say hey brain were very distended so a message is going up to the brain so that's the message coming into the brain so what could the brain do well just as before let me just draw out the trachea kind of splitting off and in this case what's going to happen is you have the vocal cords just as before let me draw them in like this right little vocal cords and these vocal cords are initially going to be open and air is coming through and this is of course inhalation right we're inhaling right now let me write that out inhaling so inhaling air using the muscles of inhalation we said primarily the diaphragm and the external intercostal muscles and then just as before the vocal cords closed so all of a sudden now you have closed vocal cords so what's going to happen if that vocal cord closes off or the vocal cords closed off well the air is literally going to not be able to come in and you know it can't come in anymore so you have this kind of bouncing off where the air literally bounces off of these closed vocal chords it can't go anywhere and when you have air rushing in and then bouncing off of the closed vocal cords you know what we call that we call that a hiccup we call that a hiccup so it's kind of interesting how this is in some ways kind of the opposite of a cough right in the COFF you had air that was being exhaled and a closed vocal cords and then here you have air that's being inhaled and you have the closed vocal cords and of course when I say the closed vocal cords it's very very instantaneous it's just for a quick moment and that's what causes the big change why we hiccup is still a bit of a mystery but at least now you have a little bit of insight into how that actually works