I ninja nerds in this video we're going to go ahead and talk and part three of the mechanics of breathing alright so if you guys are here thanks again for sticking in there with us we just really want to make this stuff makes sense ice if you guys remember we left off talking about what happened during the inspiration process and if you guys remember really briefly to quickly recap that at the end at the a peak point of inspiration what was the pressure inside of the intrapleural cavity if you guys remember we called it the
P I P if you guys remember we've denoted it as negative four millimeters of mercury during the rest right so it was negative four millimeters of mercury during rest then what happened when we inspired the actual thoracic cavity volume increased and the pressure decreased what did it decrease to if you guys remember that the intrapleural pressure is fix this here the intrapleural pressure all right it dropped down to negative six millimeters of mercury and this was during inspiration was that peak point of inspiration so it dropped down to you guys remember then we said not
only did this change let's show this arrow here that this is to what is actually how it changed it went from at rest negative 4 to negative 6 during the inspiration process then what happened to the intrapulmonary pressure will thoracic cavity volume increase so the long started to expand right what happened the visceral pleura was pulled pulled closer towards the parietal pleura if you guys remember thoracic cavity volume increases the actual lung volume increases so the intrapulmonary pressure should decrease but originally at rest what do we say it was we said at rest the people
which was denoted as was zero millimeters of mercury right in comparison to the atmospheric pressure right and then this was at rest but then at the peak point of inspiration what do we say we said it actually thoracic cavity volume what the thoracic cavity volume increase so the intrapulmonary pressure should decrease what do we say it was during that actual process we said it changed to about what negative one millimeter mercury so this was a during the inspiration process but that wasn't it remember we said that because the atmospheric pressure if you guys remember the
atmospheric pressure was actually what 760 millimeters of mercury and if you guys remember how can we rewrite these numbers so you know we say zero millimeters of mercury doesn't mean that there's no difference between that in the atmospheric pressure so it's actually 760 millimeter of mercury here but over here it's one less than the atmospheric pressure so it's 7:59 millimeter mercury right so there's a pressure difference what do we say we said that the air would flow in actually right into the alveoli until the pressure in the alveoli equalled the pressure in the atmosphere so
would rise right so the peak point of inspiration what would they convert to we said the peak point of inspiration it would switch and it would actually allow air to keep flowing into the alveoli until the intrapulmonary pressure was at 7:59 or negative one same thing went back to what it was out actually in the atmosphere so what should the people be at the end point of inspiration it should go back to zero millimeter of mercury which again if we rewrite it in terms of this it would actually be 760 millimeter mercury okay so that's
what happened there now one more thing before you move into expiration is if you guys understand something real quick this is what happens during quiet inspiration so there's all these events that we just talked about here this was occurring during quiet inspiration why am i mentioning that because you know there's what's called forced inspiration let me think about it but I'm just sitting here just normally breathing I'm not really putting a lot of effort into it right but if I really want to take some air in let's say I really want to take some air
I'm getting ready to like I don't know lift something really heavy and I want to get some air going into me right I take as much air as possible I was a little bit more forced so a forced inspiration doesn't just involve my diaphragm on the external intercostals if you guys remember because they were the ones that were contracting and changing the thoracic cavity volume and therefore the pressures they know this other muscles involved so again in quiet an inspiration what muscles were involved in quiet inspiration the muscles that were involved in quiet inspiration was
the external intercostals and what was the other one the diaphragm right the diaphragm was the big one that was actually one of the inspired 20 muscles during the actual quiet inspiration but whenever we have to force the inspire we have to pull in some accessory muscles so during this forced inspiration process let's write this one down during the forced inspiration process it requires some other muscles you know I'm the sternocleidomastoid it actually connects to the sternum and so actually what helps when it contract it actually could help to pull the sternum out a little bit
and there's some other muscles too they're actually here in the lateral side of the neck they call them the scalene the anterior middle and posterior scalene they also are connected to the rib so they can help to pull the ribs a little bit and if you're very well-developed of individual you can have what's called the pectoralis minor they connect to the third fourth and fifth ribs so they help to be able to pull the ribs up just a little bit okay so they can play a role in a forced inspiratory process so again what were
those muscles that I mentioned again one of them was the sternal glide oh massive we're just going to write SCM okay the other one was the scalenes and again there was an anterior a middle and a post here scalene and then the third one was going to be again the pectoralis minor okay why am i mentioning this because all it does is just going to add on to this so if you think about these guys if these guys are involved during forced inspiration what are they going to do let's otis i said that the sternocleidomastoid
pulls the sternum out a little bit so helps to elevate that pull it up a little bit outward so that increases our thoracic cavity volume scaling is also pull up in the ribs petra also pulls up on the ribs a little bit if that's doing that what is it actually doing to the thoracic cavity volume all of these things are working to do what their primary function is to do all of these guys increase thoracic cavity volume even more than the diaphragm and the external causes going to do are doing so that's the case let's
pretend for a second that those muscles contract what's going to happen to the thoracic cavity volume it's going to increase greater than normal so what would you expect so let's actually have another line here let's do this one in green for us actually no let's do this one in this maroonish color let's say that this is during forest inspiration so this is during forced inspiration so it goes from here rest we take in a certain amount of air but we go even more than that let's say that the interaural pressure decreases even a little bit
more because the volume is increasing a little bit more so the pressure should decrease a little bit more so say it was negative sex let's say it goes down to negative seven now just suppose that it goes down to negative seven millimeter of mercury and during what is this during this is during forced inspiration alright sweet okay same thing what about for the people well we said it was a zero during rest okay well let's pretend for a second that we pull on the sternocleidomastoid scalings pectoralis minor and we've taken a little bit more air
and what's going to happen to the thoracic cavity volume is going to increase so what should happen to the actual pressure inside of the actual alveoli it should decrease even more how much more should a decrease well decrease the negative wondering quiet inspiration let's add one more negative point so say we went down to negative two so that's the case it goes down to negative two millimeter of mercury and this is during forced inspiration but again you guys already know that whenever we reach that point of where there is a pressure difference between alveoli or
the intrapulmonary pression the atmospheric pressure what's going to happen air has to rush in to equalize so think about this for a second this was a negative one so compare this 760 to 759 if this one drops down to negative two what is that in this terms of 750 and all that stuff this would be 758 millimeters of mercury who has this deeper pressure gradient this one into 759 or this one into 758 obviously 758 what does that mean it more air is going to flow down into the lungs until this pressure equals the atmospheric
pressure until what and we can show this arrow going back to this point here so I can show it going right back to this point alright okay so that should make sense and that's why if there's a greater pressure difference what does that mean that means more air is going to flow in you know the relationship between that I don't leave you guys hanging there there's a relationship it's called a specifically flow of gases is equal to the change in pressure over the resistance so if you have a greater pressure difference what's going to happen
to the flow so if this increases what's going to happen to this this will increase there's a greater pressure difference so what's going to happen more gas will flow in that's the whole point so whenever you're breathing in normally versus I'm taking more earing it's simple right okay that's force inspiration now here's the next question I want to ask you guys I want to pose a question to you guys I want you guys to think for a second all right so all these muscles are involved during the inspiration process a lot of muscles what muscles
are involved in an exploration process if you guys said any muscle I want you to remember that's not correct there is no muscles that are involved during the expiratory process if it's completely passive why is it passive I'm glad you asked I'm going to tell you so you know our lungs are very elastic so during expiration now we're talking about quiet we'll talk about force in a second but we're talking right now about quiet expiration so during quiet expiration are there any muscles involved no muscles involved no muscles involved need you guys to remember that
because it's the passive process so again what is it here it's a passive process so it doesn't require the activation of our muscles or skeletal muscles to contract what does it depend upon let's write this on a super bright color it completely depends upon the elasticity of the lungs what is elasticity elasticity is this desire of a structure in this case the lungs to resist being stretched in other words it always wants to snap back and what's to reclone go back to the smallest size possible okay and you can determine that because you know elasticity
is equal to the change in pressure over the change in volume so what happens if your volume decreases your elasticity increases so you want the volume to decrease that your elasticity can increase so that's the whole goal here that's what we want to happen so how does this happen let's explain that if you guys remember we're not going to take a significant amount of time here we're going to be pretty quick let me get this brown marker over here if we have over here if you guys remember we have a structure here inside of the
medulla you know this is the midbrain this is the pons this is the medulla oblongata in the medulla you have this specialized structure it's a mixture of expiratory an inspiratory neurons this structure here is called the v RG the ventral respiratory group okay so now you know that there are from the v RG dis coming these downward presynaptic neurons they're sending these presynaptic neurons down to specific sections of the spinal cord specifically in the ventral gray horn in the ventral grey horn you have these somatic neurons especially especially around c3 c4 and c5 they actually
send these axons out and they come onto the diaphragm as you guys remember right so this is the phrenic nerve and that was intervening the phrenic nerve i'm sorry that was intubating the diaphragm to cause it a contract and trigger the inspiration process then if you guys remember if it came down even more if I came down even more I'm not going to draw all of them I'm just gonna do a couple of them but you know that this is c3 to c5 this is t 1 to t 11 this is the intercostal nerves right
and we'll draw the intercostal nerves in a different color let's do these in like a red color or something I don't know do the green so again these right here your intercostal nerves right and this would be T 1 2 T 11 and you get that these guys would come up here and they would enter v8 what the actual external intercostals right and cause those that contract whenever we start getting ready to expire the whole point of expiration is there's no muscles involved so we want to shut down these actual nerve impulses we don't want
those nerve impulses to keep sending signals how do we do that there's special stretch receptors inside of the actual bronchi and around the actual lung area that pick up that increase in stretch because we inspire inspiration process and how our body deals with that let's say we have here let's draw a little stretch receptor out here look at him he's sitting here and he's having his feet in here and he feels some actual stretching so what he does is this stretch receptor this is our stretch receptor this little dude right here and what he's going
to do he's going to pick up this stretch and he's going to send these signals into the medulla we're not going to go over the mechanism right now all we're going to say is that it inhibits the vrg the inspiratory centers of the medulla we'll talk specifically about the mechanisms in other videos but for right now there's what you guys to know that the stretch receptors is sending inhibitory signals into the actual module one inhibiting these inspire Tory centers and then if that's the case what's going to happen to these action potentials coming down they're
going to drop so the action potentials going down this actual axons is going to decrease and if all of these action potentials decrease what happens to the action potential is going to the diaphragm it decreases what happens to the action potential is going to the external intercostals it decreases if all of this decreases what happens to these muscles they relax so if the external intercostal muscles what happens to this one it relaxes ah it relaxes right like I'm done contracting what happens to the diaphragm it relaxes he's like oh thank goodness I get relaxed now
what happens when these muscles relax if you guys remember what do we say about the diaphragm let's let's show it actually oh just so a small diagram right here let's say I do a smaller a quick diagram crude diagram don't judge me guys it's going to be a really quick one and let's say right here I have the diaphragm right here right so here's your diaphragm if you guys remember whenever the diaphragm was contracting what was happening to the diaphragm is remember it was actually it was actually depressing downwards right so because it was depressing
down which what was that doing sarasu cavity volume it was increasing it when this relaxes he goes back up so now if you can imagine what would happen then this would go back up and what would that do to the thoracic cavity volume it would decrease the thoracic cavity volume what's that relationship with Boyle's law okay why no Boyle's law that let's write that down Boyle's law says that pressure and volume are inversely proportional so there is an in inversely proportional relationship between pressure and volume if pressure increases what happens to the volume it decreases
if the actual pressure decreases then the volume increases you get the point well now we said that we're bringing the diaphragm back up so what should happen to the volume it should decrease then what should happen to the pressure it should increase and that's what happened let's note that so again what happens here when the diaphragm and the excellent Urkel's contract the thoracic cavity volume decreases and then what does that do to the pressure and therefore the threat of the actual pressures would increase and we're going to see how that's actually happening okay before we
do that let's say what the external air castles do remember what they were doing we showed you on the skeleton model right they were creating that that bucket handle movement they were pulling the ribs outwards and pulling the tsardom outwards and forward right upward and forward that was the increase in thoracic cavity boiling if they relaxed what's going to happen they're going to recoil they're going to come back down the Xoom is going to come back to this position what's gonna happen to the resting evety volume it's going to decrease and what's gonna happen to
the pressures inside of thoracic cavity they're going to increase so let's see how those pressures are increasing on this diagram over here okay so now if we take what we were during this actual inspiration process let's write that down over actually no we'll keep it and we'll show how it's happening over here right so during the inspiration process our intrapleural pressure was negative six millimeters of mercury right then what happens to this thoracic cavity volume it decreases so what should happen to this pressure it should increase to what point is that pressure increased well as
the diaphragm is going back up and as the ribs are at the chest walls recoiling this intrapleural pressure should actually go up to about negative four millimeters of mercury of the original volume there the original pressure so what should that pressure now be where's my blue mark this is actually going to be enter plural pressure is equal to negative four millimeters of mercury and this is during the actual change during this change in the pressures right so now whenever this actual volume decreases the pressure should increase and it should go to negative four millimeters of
mercury during the expiration process sweet nothing nothing too bad about that right okay so now why is this pressure decreasing it because the volume of our lives this pressure increasing because the volume decreased and the volume decreased because the actual chest wall was recoiling back as the chest wall is recoiling back also the diaphragms doning up and you know the lungs they're trying to recoil because the elasticity they're trying to recall so they're trying to pull the visceral pleura away from the actual parietal pleura right but remember these two layers are sticky to one another
so what does that mean it's going to pull in the parietal pleura also so when it pulls on the parietal pleura it decreases the actual volume and increases the pressure okay but then inter pulmonary pressure okay let's take a look at that originally what was it well let's come back and look at it real quick before we come over here so we don't lose sight of this it was over here at approximately about 760 millimeters of mercury or zero right well now we're actually decreasing a thoracic cavity volume so the pressure should increase you know
what the pressure actually increases - it increases to approximately about one millimeter of mercury above so it becomes positive one so now the p-pull the intrapulmonary pressure should go to positive one millimeter of mercury and again how can we write that with respect to the atmospheric pressure if we compare it with that what is the atmospheric pressure again the atmospheric pressure was 760 millimeter mercury this one is one above that so it should be 760 one millimeter mercury huh well now the pressure gradient difference is from here out there that's the diffusion principle things like
to move from areas of high pressure to low pressure so where should the air go the air should go out out into the atmosphere where the pressure is lower and how long will it actually keep doing that it'll keep doing that until the pressure inside of the alveoli are inside of the lungs equalizes with the pressure in the atmosphere and then there's no net diffusion right so now let's say that that happens let's do this in pink let's show the change so during the exploration process so during this process when the thoracic cavity volume is
decreasing right this is what you're going to get so this is during the actual beginning of exploration right so this is at the beginning point of exploration but when the air is actually leaving when the air is actually leaving because when thoracic cavity volume is decreasing that's when the pressure increases but then where does the air have to go as to go out into the atmosphere so then the pepole will change an air will start flowing out on pill the intra pulmonary pressure equalizes with the atmosphere so it should become zero millimeter of mercury or
again how would you rewrite this this will be rewritten as 760 millimeter mercury and this is at the end of inspiration so I'm sorry exploration this is at the end of expiration and of expiration because the moment Winship when it becomes equal there's no going to be no net diffusion because again things like to go from high to low pressure when it's equal there's no net movement it's the equilibrium okay so that's the process there okay so what things were contributing to this if we remember let's come back review and then we're going to go
into one last thing and then we're done here all right what do we say quiet expiration no muscles it's passive why because of the natural elasticity lungs it wants to recoil when it recoils it pulls the parietal pleura right and start pulls the visceral pleura away from the parietal pleura but if you remember those layers are sticky so it's going to try to pull the parietal pleura with it not only that but the chest wall is going to wreak whoa why because the external intercostals are relaxing and the diaphragm is relaxing so therefore the thoracic
cavity volume will decrease and all those pressures will increase okay but you know our body has another way of dealing with when we need to get extra hours so if I'm just trying to breathe Norlin just trying to expire so let me just stay here for a second go just a normal that's was just a normal inspiration exploration but now I want to breathe out let's say I'm doing ABS I'm doing some ABS I'm trying to get that you know I'm trying to get more fingers than ABS right and I'm sorry more abs and fingers
can right and I'm trying to contract my abs if I do that I'm going to exert I'm going to try to breathe out as hard as I can so I have to exert more effort so it has exert more effort to exhale that extra air it's require some extra muscles so forced expiration does require muscles quiet expiration does not involve any muscles so let's write that down so again what did I say forced expiration involves muscles so what muscles would be involved in this primarily the abdominal wall muscles so the abdominal wall muscles so which
ones you know like the it could be the external oblique the internal oblique and even the transverse abdominus into a little degree the rectus abdominis until a little degree of the rectus of them so you all can say the transverse transverse abdominis and a little bit of the rectus abdominis okay so now if these muscles are contracting how is this actually house it's actually happening there's one more muscle I forgot I'm sorry one more muscle it's called the internal intercostals we'll talk about these and we'll say how this plays a role in this relationship but
what what's the overall effect of these guys okay let me explain the internal cost is first because it's the easier one and then I'll explain the abdominal wall muscles alright so I wanted to bring in an actual skeleton model so we could go again so we did with expert R we did with inspiration let's see how that works with expiration so if you guys remember here's our ribs right here right and if you guys remember there was the muscles that were the external hostels right and they were actually elevating the rib well we have other
muscles which are in between the ribs which are called the internal intercostals the only difference is if you remember the external cause we're pulling the up the lower rib upwards the internal intercostals will pull the upper rib downwards when that happens it pulls the actual ribs downwards a little bit more and as it pulls the ribs downwards a little bit more and tries to push the sternum inwards as well as trying to push the ribs a little bit more inwards what happens to this thoracic cavity volume it it would decrease and just to give you
a little bit more of an example we'll bring this here chest plate here and so you can see again if you look we're going to have here's your ribs and here's the internal and our costal muscles and again when they contract they pull the upper rib downwards depressing the actual rib cage and by doing that they decrease the thoracic cavity volume okay so I just want to give you guys that as an example let me get back get this out of the way and we'll get back into this video all right so now that we
know that we know that the internal intercostals are actually helping to decrease the thoracic cavity volume that was their main goal so they're doing that so let's write this down Oh fix my spelling here internal and did it again and internal intercostals all right now these are just designed to be able to decrease thoracic cavity volume all right so we deal now these other ones so let's explain how these work so these are pretty cool when they contract the external oblique internal bleed transverse abdominus and the rectus abdominus when they contract they help they actually
create a pressure they increase the pressure inside of the abdomen so it's called the intra-abdominal pressure right when that pressure increases it pushes upwards upwards and backwards on the diaphragm so imagine here's the diaphragm right here and the abdominal wall muscles are trying to push on the this diaphragm in its actual resting-state er this actual expiratory state right so I think it's actually relaxing I said the diaphragm is relaxing but then the abdominal wall muscles contract and they increase the pressure inside the abdomen and they start pushing and pushing and pushing and pushing imagine me
yanking this diaphragm up I'm yanking the diaphragm up what am i doing to the thoracic cavity volume I'm decreasing it so I'm trying to push the diaphragm up to decrease thoracic cavity volume what is that going to do the pressure it's going to increase the pressure let me write this down here with these guys again what is the goal of all of these muscles here all of these ones is to increase the intra-abdominal pressure intra-abdominal pressure which will then push on the diaphragm and then when it pushes on the diaphragm it actually does what to
the thoracic cavity volume it decreases the thoracic cavity volume alright so we deal now when that happens let's say that there the actual thoracic cavity volume generally whenever the diaphragm is just normally relaxing and the external intercostals are normally relaxing this pressure was negative for right and then this pressure went to what positive one right now eventually went to zero well now we're going to decrease the volume even more so now this pressure should actually go up a little bit more it should actually become a little bit more positive let's say for example that it
happens during the forced expiratory process so during the forced expiratory process what would we expect it to change a little bit from let's say that it changes to about negative three just suppose negative three millimeter mercury so not even a little bit more positive and again this is during the forced expiration and this is because the actual this volume here is decreasing because the chest wall was trying to push inwards and then also the diaphragm is trying to push upwards also so the volume is decreasing the pressure things get increased a little bit more with
this one it was actually positive one right during that act for exploration process let's say that we actually decrease the thoracic cavity I'm even more his pressure should actually go up a little bit more maybe like +2 so let's say for example that this one actually does increase let's say it increases to about +2 from the actual just normal expiration project so we're just comparing them this is negative for negative 3 this one will be +1 this one should be +2 millimeter mercury and this is during what forced expiration okay why am I telling you
this again what is the atmospheric pressure let's write this out here atmospheric pressure is 760 millimeter mercury compare the differences here 761 vs. what is this again if we rewrite this what would this actually be written as we could technically say this is actually 760 - because it's a 2 above the normal atmospheric pressure so 7 62 millimeter of mercury compare 760 - from 761 which one is actually going to flow out more well this is going to have more air to flow out so this is going to have more air so more flow from
this lung and that's what explains during this actual forced exploration process why more air goes out so more air leaves because why the gradient here is to the gradient here is one more air will flow out until the pressure inside of the lungs equalizes with the pressure of the atmosphere which should be what it should go until it equalizes with the atmosphere so the intrapulmonary pressure at the end of the forced expiration should be zero millimeter mercury zero millimeter of mercury and again this should be at the end of forced expiration and again what is
if we just reiterate again what is this 760 I mean what is this zero millimeter mercury it is just same thing as writing 760 millimeter mercury alright an engineers we cover a lot of information in this video I really appreciate you guys sticking in there with me I hope all of this stuff made sense I know it was a lot of stuff I Anna and I hope it made sense now I hope you guys if it did please hit the like button comment down the comment section and subscribe all right ninja nerds as always until
next time
