Physiology, Lecture 7, Gas Transport (Lecture Notes)

8/8/2019 Physiology, Lecture 7, Gas Transport (Lecture Notes)

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Physiology lecture (7)

The respiratory system

13-10-2010 wed

In the last lecture we discussed the

elasticity of the lungs, andcompliance(how much effort is required tostretch or distend the lung) and we said

the more lung compliance the easier webreathe (less energy), and this compliancecould be increased in abnormalities likelung diseases, in such diseases theelasticity of the lungs will not be normalit's not easy to flat that lung so the

breathing will be difficult and we needmore energy to do the simple respiratorycycle, and we said that when you breathyou take the normal amount of air you needunder quiet conditions, and it's calledtidal volume. So you should remember whenyou look at the respiratory system as asystem it's divided into two parts:

1- The 1st part is the air conductingchannelswhich has nothing to do


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with gas exchange, just to conductthe air inside the lung.

2- The good one for physiology isthe alveoli, so if you look back tothe structure of the respiratorysystem, {the lungs the alveolar

part and the air conductingchannels on top}.

When you breathe you do the inspirationyou will take the fresh air fromatmosphere inside your chest, if it'squiet breathing you will take about 500mlsof air these 500 will go down through theair conducting channels until they reachthe alveolar compartment by the end ofinspiration " follow that procedure" I

took half a liter of air inside my lung bythe end of inspiration there is smallamount of air still in the air conducting

channels .. Right because they areopened and they are full of this air sothe 500ml will never reach the alveoli as

a total 500 some of it will remain in theair conducting channels this amount of air{a volume} inside the air conductingchannels we call it deadspace why this

term ? . Because this amount of air even


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if it is full or rich of O2 its not usedfor gas exchange, there is no property ofthe tissues in the air conducting channelsto cause the O2 to go to blood and the co2to go to the channels so the amount ofoxygen in that area "air" will remainconstant, it will not decrease by oxygenconsumption, but the air inside thealveoli in the part that reaches thealveoli will be exposed to the alveolar

"what we call respiratory membrane" oxygenwill leave and carbon dioxide will begained; if we take that air way channelsand we measure the volume of that channelsin the adult person it is equal to 1500mlso the dead space in normal physiological

condition equals 1500ml now if you breathe500ml 150 of them will be in the deadspace and the rest 350 will go down to thealveolar system, so this is the amount ofair we use for oxygen exchange this is theamount of air we increase by the CO2

percent in the 350, in other words if weasked a question: " if a person breathes

12 times per minute this is the normal

>


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now 500mls its the tidal volume itwill get in and out in each respiratorycycle, if the person breathes 12 times perminute so how many mil will be gettinginside the chest and outside the chest inthat minute? It will be [500 X 12]

because each time I take 500 and it's 12times, so it will equal about 6 liter ofair we get them inside our chest andoutside this amount of air you get it

inside and about side per minute is calledpulmonary ventilation rate the rate ofpulmonary ventilation now consider thatfact . When we breathe those 500 about150 remains in the air conducting channelsand they are not useable so the only

useable amount is 350 so we can calculateanother term in physiology which is calledalveolarventilationrate the amount of

air which gets inside the lungs andexposed to the gas exchange it's calledalveolar ventilation rate how much per

minute? If we are talking about 12 timesper minute 500 tidal volume but each time

I take the inspiration 150 will be lost sothe amount getting inside the alveoli is350 each respiratory cycle, so the


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alveolar ventilation rate = {350X12} , howwe did that ?! By taking the tidal volumesubtracting from it the dead space, thenthe result times the respiratory rate "isthat clear?!", now for the exam if I askyou to calculate any of these terminologyif the number is not in the stem of thequestion don't put it yourself in otherwords if I want you to use a number itshould be in my question not memorizing

the text book numbers if the dead spacenot there don't use the 150 because it isthe average and when I want you tocalculate something it's about a patientor a person which could be not 150 itmight be this or more "is that clear for

the exam ?!" .Now the second objective of this lecture. To give you an idea of the gas mixture

in the atmospheric region, in the alveolarregion, in the capillaries of the lung, inthe systemic circulation, and in the cell,

before giving these numbers to you I thinkyou remember from biology that there issomething called partial pressure of the

gas, and it is inversely proportional tothe volume, in other words if you take a


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volume of air in a container and youmeasure the partial pressure of that gaslet's say X now if you push that volume bydecreasing the volume by half the partialpressure of the gas will be doubled, andif u expand that volume more the partialpressure will be less. So if we take theatmospheric pressure "the normal is 760mlhg" on the sea level "this is ourreference", and we are talking about a dry

weather day, the content of atmosphere isNitrogen about 80%, and Oxygen about 20%,zero carbon dioxide "almost", and no watervapor {a dry day}, but in winter time whenwe have vapor in the atmosphere that vaporgas will replace amount of pressure for

itself, now if we measure theconcentration of O2 and N2 we said 80:20so the 760ml hg was divided between oxygenand nitrogen but not equally, nitrogenwill take 80% of the partial pressure, andoxygen will take 20% of that pressure, so

{760X20} it will give you the partialpressure of oxygen, normally it's about

160ml hg and the remaining will be fornitrogen, in some text books you will findvery tiny small amount of partial pressure


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of CO2, now when you breath this dry airinside your lung, when the air gets insidethe air way channels, your air waychannels are wet they always have vaporwater in, so the mixture will be changedthe oxygen will not be 20% but less thenitrogen will not be 80% but less dependson how much water vapor there this is onefactor the other factor when air getsinside your lungs there is amount of

carbon dioxide which gets there from yourbody after metabolism this CO2 will leaveyour body by the respiratory system sowhen the atmospheric air gets inside yourlungs now we are talking about differentpartial pressures of these compounds, and

you should remember it you should read itin your book those partial pressures theimportant one for me for my lecture is100ml hg of O2 and 40ml hg of CO2 rememberoutside your body the O2 partial pressurewas 160ml hg inside the lung it is 100ml

hg why it is less?! Because we have vaporwater and CO2.

If you go down a little bit and reach thecapillaries which surround the alveoli what are these capillaries? These coming


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from the pulmonary artery ... they come tothe lungs they are not rich with oxygenthey lack it, they came to the lung justto get more oxygen so if you measure thepartial pressure of oxygen in thecapillaries of the lungs which areapproaching the alveoli the partialpressure of oxygen in that blood undernormal conditions is 40ml hg and if youmeasure CO2 partial pressure it's about

46ml hg "the doctor summarizes what hesaid in drawing"

So when you do inspiration... The O2inside the lungs is 100ml hg, the CO2 is40ml hg for the coming blood the O2 is40ml hg and CO2 46ml hg this is thenormal condition quiet no exercise, themetabolism is the basic we need in ourday, this is the normal condition. If youare exercising then that blood will carryless oxygen, at the same time the sameblood will carry more CO2, you know why

because exercising utilize so the O2 willbe reduced, exercising will produce moreCO2, which goes with blood to the lungs,at the same time if you look to thealveolar compartment if you are


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breathing normally most of that time youwill get CO2 from capillaries to out andO2 from outside in if you hyperventilate{instead of 12 times per minute you do it20 times or 30 times unfortunately theDr. will not explain more about it becausethere is no time} , hyperventilation isgood and bad, we will go in details of thegood part of it so you will increase theamount of oxygen getting inside your lungs

"common sense" under normal conditionwhen I breath normally 160 available butwhen they get inside I get only 100 nowif I do hyperventilation this 100 will bemore what could be the max?! What is themax O2 partial pressure inside alveoli if

I hyperventilate?! . 160 because the maxI have out is 160, unless I breathe pureoxygen in the hospital, now at the sametime when you hyperventilate you get moreoxygen, but at the same time you depletemore what ?! More CO2, so the CO2 there

will be less than 40 Now we go down when the blood goes throughthe distance beside the alveoli {look atthe wisdom of Allah in this}, through thecapillaries in the lungs the reason that


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blood comes there is to take O2 anddeplete CO2, the gas exchange which occursfrom alveoli to capillaries it will getfully saturated by 1\3 of the distance ofthe blood flow,

} 3 {

You might ask why?! Because Allah knowsduring exercise and heavy duties the blood

flow will be increased not only 3 timesmaybe 5 times, if you increase the bloodflow more "and god made the saturation bythis point "by the end of the alveoli" ",so most of the blood when I need moreoxygen will leave the lung without being

saturated, so 1\3 is more than enough toget full saturation of oxygen and get ridof CO2 (this is one importantphysiological point) the other one whenI said fully saturated it means fullequilibrium with the alveolar compartment,so when I say equilibrium I'm talkingabout passive transport of gas 'O2 andCO2', and when you get to the equilibrium

by this point I will have O2 not 40 but "8adeeh ?!?!! Let's just take some extratime to explain this o.O ma bedko ?! :P


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the Dr. ma beshra7 mshan el exam 3shane7na net3alam .. al mohem " .. if we aretalking about normal equilibrium youremember if we have a membrane and we havea 100 partial pressure of O2 and 40 on theother side . What would be theequilibrium?! 70:70 In lungs equilibriumdoesn't mean that because when I reach 70on both sides I'm still breathing I'mstill doing expiration so 70 will be out

and 100 will be back the normal partialpressure of oxygen when a side is 70 andthe other is 100 it will take 170\2 about 80~~ 80~~ of the channels outanother 100 coming down, so by the end ofthis distance I will have 100ml hg oxygen,

and the same thing applied to CO2 I willhave 40ml hg .. So saturation by the endof the blood flow to the alveoli it willget the same partial pressure of thealveolar compartment, for O2 and CO2.

So now the blood leaving the lungs going

back to the heart and then to the tissues systemic circulation, we have 100ml hgof oxygen and 40ml hg CO2 now itreaches the cell, in the cell we have 40mlhg O2 and 46ml hg CO2 of course those


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could be lower depending on the metabolicrate of that cell, and here theequilibrium is the same as in the lungs"that will be 40 O2 and 46 for CO2" and itwill go back and this cycle will berepeated many times every day every secondevery minute in your life.

Gas exchange which is between alveoli andthe blood oxygen and carbon dioxide thisis our concern they should cross therespiratory membrane, they should crossthe epithelial cell of alveoli "type1",they should cross the basement membranebetween the alveoli and capillary, andthey should cross endothelial cell layerin the capillary, then they go inside the

blood, where they dissolve in the plasma,when they are dissolved in the plasma theywill create partial pressure which is 100

and 44 carbon dioxide, In the blood gaswill be transported not as a dissolvedcontent, in blood we have plasma, small

amount of oxygen will be dissolved in theplasma, but major amount of that oxygenwill be bound with hemoglobin, so oxygenshould cross not only the plasma of theblood it should cross the cytoplasmic


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membrane of the red blood cells, andfortunately when the blood cell goingthrough the capillaries in the lungs thediameter of the capillary is so small sothe red blood cells will be squeezed inthe capillary it will not be swimming inthe plasma, why is that? Because we wantless distance between hemoglobin and theO2 coming from the alveoli, so the RBCswill change their shape and they will be

squeezed in the capillaries, so betweencapillary and hemoglobin we will have onlythe cytoplasmic membrane of the RBCs. Nowthe way oxygen transported in blood is sobeautiful "zaykom :P " in a way it helpsour life so let's discuss it in details.

Now if you take a portion of blood from ahuman being this blood will be RBCs andplasma, let's measure the O2 in the plasma

and the O2 in the RBCs, let's assume thatwe have a 100ml of O2 in that portion, wewill find out that from these 100mls of O2

only 1.5ml is dissolved in the plasma but97.5 it's inside the red blood cells boundwith hemoglobin and you remember how manyhemoglobin we have huge amount ofhemoglobin carrying that O2 and this


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binding assay between O2 and hemoglobin isreversible, so it's not oxidation it'soxygenation so remember oxygen 98% boundwith hemoglobin but only 2% or 1.5% isdissolved in the plasma even that it's afact the partial pressure of oxygen in theblood related to the dissolved oxygen thebound oxygen has nothing to do with thepartial pressure of oxygen so if youmeasure the partial pressure of oxygen in

the blood when you do that you measure theeffect of the dissolved O2 which is smallamount. The amount of bound oxygen dependson the partial pressure of oxygen, even98% is bound but they are dependent on thepartial pressure of oxygen >>> partial

pressure of oxygen depends on thedissolved oxygen. So the more you dissolvethe O2 the more partial pressure you getin the blood >>> the more PP you get themore bounds O2, now this relationshipbetween O2 inside RBCs inside the blood is

a special one and it has a curve : oxygenhemoglobindissociation curve


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How did we reach that?! We took blood inthe lab and we exposed that blood to zeroppo2 when we did that we reach a point {as u can c on the curve} let me remindyou of something when we said the

percentage of hemoglobin saturation if wetake 1molecule of hemoglobin and there is3 molecules of O2 bound what the

saturation level here?! 75% because fullysaturation is the 4 sites, when we have 4molecules of oxygen this is 100% 3 thisis 75% 2>> 50% 1>>25% 0 >>>0%, thisis in one molecule of hemoglobin we are

talking about 300 millions of molecules.Now this saturation could be calculated asan absolute number not percentage, how canwe do that? If I give you this fact: if


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you take 1gram of hemoglobin and yousaturate that one gram with oxygen 100%that gram will take 1.34ml of O2, now whatis the normal concentration of hemoglobinin normal human blood? "la t8oolo mabte3rfo O.o" the normal hemoglobinconcentration is 15gram/deciliter if youtake a blood each 100ml of blood theycontain 15gram of hemoglobin, if you havereduction of that that will cause anemia.

I told you that 1gram of hemoglobincarries when it's fully saturated 1.34mlof oxygen now 15gram of hemoglobin in100ml of blood when I saturate a 100ml ofblood 100% saturation how many mls ofoxygen? It will be {1.34X15gram} each gram

contains 1.3 . It will equal 20mls ofoxygen per deciliter of blood this is thefull saturation of blood.

In this experiment we took the blood andwe exposed it to zero O2 now we started atthat point in the scale we measure theppO2 each time we change the situation,then we take a sample and we measure how

much O2 is contained in that sample, nowafter being exposed to zero pp there isno O2 and the ppO2 is zero now we start


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to add only 10ml of oxygen pp we waited alittle bit >> equilibrium we took sampleand we measure that amount of O2 in thatblood, we increased the pp to 40,50,60each time we take a sample and measure it,when we plotted our data the saturation ofhemoglobin or the amount of O2 inml/deciliter against the ppO2 we get thehemoglobin oxygen dissociation curve:

Why this curve is important? Look at itcarefully apply that curve inside theorganism, inside the human body, andinside the blood, if I ask you what is theppO2 in arterial systemic circulation?Your answer will be 100ml hg "fully

saturated of blood". 100ml of oxygen look at that point this is the arterialblood systemic circulation, it's full withO2 100ml hg, now when it leaves thetissues


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) (

The ppO2 in the venous blood its 40 so

when you look to this curve "above" and weput a point of the venous blood, from thearteries to venous the oxygen differencewas utilized by tissues blood wascarrying 100ml hg after leaving the tissueit was carrying 40ml hg where thedifference went?! It was given to thetissue this difference in that curve ifyou want to calculate it by number; atfirst the saturation was 100% or 20mls "atthe first one", "at the 2nd one: ", itbecame 75% or 15ml which means when theblood is fully saturated it carries 20ml

of oxygen, when if feeds the tissues andleave them under normal physiologicalconditions, it will leave 5ml of O2 to the

tissues and still have 15ml of oxygencarried ad bounds to hemoglobin. Underexercise 5ml of O2 is not enough we need

more, we don't need 7 we don't need 8 wedon't need 10, we need 15ml of O2, 75%ofthe total, if that happens that exerciseis on in this case the ppO2 which is inthe venous blood from 40 it goes down to


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30 only, just 10ml hg reduction of pp theamount of O2 released will be significant,so this in the blue color in the curveit's sharp just to give us more O2 if weneed them by not changing the partialpressure of O2 significantly. And thefirst part which is the rose one "red" ittells us that if the reduction of O2 from100 to 70 to 75 to 65 it will notaffect the amount of O2 carried by blood

"this is the wisdom", we want the O2 to bein our hands inside the blood, whenever weneed more we will take more

But if there is a small reduction of O2{from 100 to 70}, we don't want to beaffected, so the saturation of O2 will not

be changed on the plateau level of thecurve, even you reduce the partialpressure from 100 to 60 you still have 90%

full saturation of O2, which is good forthe tissues which is good for life, {tothe curve} but in that sharp sloop any

difference in the partial pressure of O2will cause a significant change of the O2released, and that what we need, when weneed more O2 we can get them from thatpart.


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The Dr is sure when we read the text bookwe understand it more .

But if you understand what the Dr said no

need to go to the book.In the first lecture of respiration the Drmentioned a term of hemoglobin affinity .Breaaaaaaaaaaaak .

The affinity of hemoglobin to bind oxygen how hemoglobin strong to carry oxygen,we said that it's not good to carry the O2

and stop, it's good to carry the O2 in thelung region, but when are close to thetissue region it's good to release thatO2. If I get a situation which leads toincrease the affinity in the lung area

the hemoglobin will be strong and it willtake oxygen, when that hemoglobin moves tothe tissue region and there if there is asituation leads to decrease the affinityso the release of O2 will be available,now there are many factors which affects

the affinity of hemoglobin, not many theyare 4 one of them is carbon dioxideconcentration or the ppCO2 it's the same,if you increase the carbon dioxide


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concentration you will decrease theaffinity 1

2 if you increase the acidity you will

decrease the affinity, so when the Ph islow the affinity is less.

3 if you increase the temperature the

affinity will be less.

The 4th is a chemical called 2, 3bisphosphoglycerate it's available in the

tissue, if the concentration is increasethe affinity will decrease.

Let's take these factors 3 of them, andlet's take the lung region and the tissueregion, in the lungs we always have

ventilation {if we want to ventilate aroom we make the air inside it fresh}, sowe expel out CO2, and gain O2 this is therespiratory cycle, so the CO2concentration will be less, and thatincreases the affinity, so a decrease ofthese factors will increase the affinity.

So in the lungs we have less CO2, we willhave more affinity. Go down to the tissueit's the factory for metabolism where theCO2 production is continues so the CO2concentration will be high because it's


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high the affinity will be less, so in thisfactor the CO2 in the lungs hemoglobinwill be strong, and it will be weak in thetissue region.

Let's take the 2nd one which is theacidity it depends on hydrogenconcentration and H concentration dependson bicarbonate, bicarbonate depends oncarbon dioxide, we know the will knownreaction CO2+H2O2 => H2CO3

H2CO3 will be dissociated to hydrogen andbicarbonate, so in the lungs we don't haveCO2, when we have less CO2 we will haveless H, so we will have less acidity, morePh, and that will increase the affinity of

hemoglobin, going to the tissue theproduction of CO2 will create a lot of Haround, and that will increase the acidityso the affinity will be less.

The 3rd factor is the temperature, when youare ventilating you will cool the body

temperature, so if you take the lungs as aregion during the ventilation you willcool that temperature it will be less than37', and that will increase the affinityof hemoglobin, but if you go down to the


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tissues where the metabolic rate is high,a production of energy, energy producesheat, so more temperature less affinity,so Allah gave us that gift of changing theenvironment of the lung region compared tothe tissue region, by doing so this morehemoglobin without knowing by thosefactors only, in the lungs they willincrease the strength of that hemoglobin,those factors in the tissue they will

decrease the affinity, and the 4th one isstill with a big question on how it workswith the same explanation we don't knowbut still it has an effect on hemoglobinaffinity.

Now the unfortunate one is the binding

affinity to O2 is X, where is the bindingaffinity for CO is 240X, so when youcompare the strength by which hemoglobin

carries the O2, it will love to carry CO240 times more "w mena el 7obe ma 8atal :P", what does it mean in real life? It

means if you have 1molecule of CO and240molecules of O2 the hemoglobin willtake the CO almost equally, but if youhave 2molecules of CO and 300molecules ofO2 hemoglobin will go and take the CO


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which is very bad, if we have CO in ourblood, the hemoglobin will take the CO andit will not release them, no matter howmuch you increase the O2, the max amountof O2 you can intake in your body is 160,unless you breathe pure O2 it could beincreased to 500 , 600 , or so.

So carbon monoxide poisoning is verydangerous, why because it is happeningevery year, when people try to be inenclosed area, especially in winter time,when they sleep in small rooms, andkeeping the heater on, during the night,the heater produces a lot of CO, theperson is sleeping without knowinganything, breathing the CO with O2, step

by step you are increasing the amount ofhemoglobin bound to CO and decreasing theamount of hemoglobin bound with O2, until

it reaches that point which is killingthat person, with our noticing neitherpain nor stress, they die in peace (^^;)

because of carbon monoxide poisoning thisis real fact, and it is happening everyyear in our country, especially with thosewho use the heater without expelling out


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the gas, the problem is the affinity ofhemoglobin to carbon monoxide.

Look to the oxygen hemoglobin dissociation

curve, the red one is the one in the lungregion, the binding or saturation ofhemoglobin in the lung region, the bluedashed one is in the tissue level, becausethe effect of these factors there is ashift to the right, which means theaffinity is less.

Oxygen in our blood as we said 1.5% isdissolved, about 98% is bound, now if yougo to the CO2 which is the other part ofrespiratory function, CO2 will be in 3forms in the blood, 1)which is the minimum

one which is dissolved in the plasma about10% , 2) the other is bound to hemoglobinwe said that hemoglobin binds to differentsubstances, about 30% is bound withhemoglobin, 3)but the major part of CO2 isdissolved in the blood as bicarbonate andit's the combination between carbondioxide and water, with the presence ofcarbonic enhydrase the enzyme.

Now we finished with the mechanism ofbreathing, we're done with the different


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content and concentration of differentgases in different regions, we talkedabout the gas exchange through therespiratory membrane, and we talked aboutthe blood transport, O2 transport, and CO2transport.

Now we will talk about the main issue ofour respiratory function it's not enoughto know the mechanism of breathing it'snot enough to know the regulation ofexchange and transport, it's moreimportant to know how we regulate thewhole function in our life, even it iscomplicated it is simple when you thinkabout it in a simple way, always when wetalk about control system you should

remember control system: either nervoussystem or hormonal and chemical system,let's take the first part which is the

nervous system effects on respiration, ifI ask you to stop breathing you can dothat but you can't hold your breath

until you die, this is the difference, youcan control your breathing ratevoluntarily, I can ask you tohyperventilate and you can do that, and Ican ask you to hypo ventilate and you can


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do that so there is a part of the nervoussystem effect which is voluntarily part,but it is limited when we are talkingabout survival it's not allowed to thatvoluntary to continue, thats why peoplewho wants to commit suicide will hangthemselves and put their hands backtighten them, just to keep anything farfrom asphyxia which is the pert where youcut the inspiration otherwise you can't

die easily by just holding yourself up todeath. This voluntary part of the nervoussystem you can hypo you can stop you canhyper ventilation.

Without thinking of nervous system we arebreathing without knowing that we are

breathing, why is that? Because there arespecial centers in the nervous systemlocated in the Medullary part of the bone,

those centers are respiratory centers, wehave "slide 36" the blue ones called thedorsal respiratory group, and the ventral

respiratory group.


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Dorsal one if you take it andlook at it, what it does it has onlyinspiratory neurons, so what it does? When

it's stimulated it will cause inspiration,when it is inhibited it will release theinspiration, so remember the mechanics ofbreathing, normal quiet breathing is justa contraction of the respiratory muscle


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after finishing it relax so this is thepart for quiet breathing, on the musclecontacts > inspiration, off the musclerelaxes and thats it.

The ventral respiratory group it has bothinspiratory neurons and expiratoryneurons, if the inspiratory neurons are onwe are talking about forceful inspiration,when they are of it's not enough when theexpiratory neurons are on then we do theforceful expiration, few years ago theydiscovered what Pre-Btzinger complex(center) the small blue one on the topthey found out because the dorsal groupthey have regular stimulus on/off "we callthat in physiology circadian rhythm

sleeping, waking, breathing, and walkingall of these are on/off mechanism", theyfound that this small center it's like the

peace maker you it in the heart whichgives the signals this is the one likethat center for inspiratory breathing.

In the upper part of the bones we have:Pneumotaxic center, andApneustic center,

pneumotaxic center if you stimulate itwill switch off the dorsal group, nowremember that the group does the


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inspiration, so if the pneumotaxic centeris on you stop the inspiration, youdecrease the rate of inspiration, insteadof breathing one second you breath 5seconds by stimulating that pneumotaxiccenter. Apneustic center the other onedoes the opposite if you stimulated it itwill inhibit the switching off of thedorsal group, dorsal group doinginspiration when they are done they are

inhibited, Apneustic center if it isstimulated it will not lead to thatfinishing so the inspiration will bedeeper and will not be stronger, so theseare the centers in the brain.

Now there is another type of receptors

located in the air way conductingchannels, the functions of thesereceptors, when you inspire deeply,

remember the tidal volume which is halfliter, if it is more than 1liter more thanthe tidal volume inspiratory reserved

volume with it, the air way conductingchannels will realize that there issomething wrong this is too much air itcould rupture the lungs, so the receptorsthere will send a signal to stop the


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respiratory center from stimulation, theydon't allow you to inspire deeply longtime, they try to inhibit that to keep thelungs in shape, this is the nervous partof regulation, it's easy and simple.

Now the other one which is the chemicalcontrol, when we say chemical the ultimatefor respiratory function is to keep theoxygen normal and CO2 normal, we don'twant less O2 and we don't want more O2, wedon't want more CO2 and we don't want lessCO2, how is that achieved there arespecial receptors which is calledperipheral receptors " look to the wisdomof our god" they are in only two places:the aorta (aortic bodies), and in the

Carotid arteries "which feeds the brain",if there is any change in the bloodcirculation, the brain should reserve

exact amount of blood, it doesn't matteryour legs are dying, your liver is dying,the brain should reserve enough O2 so the

amount of blood going to the skull bythese carotid arteries always constant andgod put these receptors in that place,what is their function? They can sense adecrease in oxygen pp, if they do so they


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will send a signal to the respiratorycenter that there is a reduction inoxygen,

If that signal is received the respiratorysystem will start hyperventilate to getmore oxygen, but when I draw the partialpressure of oxygen, we said that thesystemic arterial blood contain 100ml ofO2 the veins blood contain 40ml, if these

receptors sense the reduction of oxygen"which is related to the O2 consumption soit will be fired every time because we

consume O2, the O2 is reduced alwaysbecause we utilize it putting thesereceptors in these two places >> at thatplace O2 will never be reduced; becausethe blood flow in these points is very

Aortic bodies

Heart

Aorticarch

Carotidartery

Carotid bodies

Sensorynerve fiber


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fast and in this fast blood there is O2its rich of it, when these receptors willsense the reduction of O2? If there isreal reduction of O2 in the atmosphericarea or in the lungs area.

" 100 90807065

"

They respond only if the ppO2 is less than

60ml why is that? Let me remind you whenwe talked about O2 hemoglobin dissociationcurve we said if you reduce the amount ofO2 from 100ml to 60ml the saturation levelof O2 still 90% so why should Ihyperventilate if I have 90% saturation of

O2 I want to hyperventilate if thereduction of O2 is less than 60ml, if thepressure is less than 60ml they will firethat signal, and that signal willstimulate the respiratory center and youwill hyperventilate. At the same timethose receptors they are sensitive butwith less sensitivity to CO2 concentrationif it is increased, and H concentration if

it is increased, but not that much asoxygen reduction.


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Now the peripheral chemical control whichis located in the carotid and aorticbodies they are "" sensitive "" only tolow O2 very weak to CO2 and H, why isthat? Because there are differentreceptors they are located in the brain.There are receptors they sense theconcentration of H, they don't sense theconcentration of O2, and CO2, they senseonly the H concentration. (Follow what the

Dr says word by word): we have bloodcirculation feeding our tissues includingthe brain but we have special structurefor blood circulation in the brain calledblood brain barrier, it don't allow tomany toxic materials to get inside the

brain, one of those toxic materials is H,so if you increase the H concentration inthe blood it will be circulated but willnot get inside the brain, "decrease the Phincrease the acidity" it will notinfluence the brain extra cellular fluid

because the brain blood barrier does notallow the H to get inside, now if you

increase the CO2 concentration in theblood its easy permeable through the bloodbrain barrier, CO2 will be elevated in the


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blood CO2 will be elevated in the brainbecause of the CO2 exchange through thebarrier, when the CO2 concentration ishigh if you remember the equation:CO2+H2O => H2CO3

H2CO3 => H + CO3, increasing CO2 in bloodincreases CO2 in the brain, with thepresence of carbon anhydrase, it willtransverse the CO2 to H, and it "H" willbe elevated in the brain only if CO2concentration is high, if that happensthose chemical receptors will bestimulated very strongly to dohyperventilation because this signal meansH is high because of CO2, I want to expelCO2 out, so hyperventilation starts and

you lose CO2.

Now whatever we said about chemical ornervous or anything the opposite willcause hypo ventilation, and this is theway we live by hyper or hypo or normalbreathing, by sensing the situation ofgases inside our body inside internalenvironment, with this perfect structure

of god's gift to help us to do ourbreathing either we are sleeping or we areawake.


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Now, there is a term which worries allmothers in the world called sudden deathinfant syndrome, which means newbornnormal without any disease, the parentswake up in the morning and he is dead inhis bed no sign no symptoms at all, whenthey discovered the reason it was thefollowing,

Just let me remind you of something Imissed when we talked about control that:too much of reduction of O2 not 60 not 50but 20ml it will cause depression ofrespiratory system, so there is a limitfor hyperventilation. Increasing CO2 up to50,55,60,65 it will causehyperventilation, but 70ml hg of CO2 will

cause depression of respiratory, now thosenewborns if they are premature thedevelopment of physiology is not that

complete, which means that an increasedCO2 will not cause the respiratory centersstimulation because they are premature,

now during sleeping all of us we have aperiod called "Sleep apnea" apnea means tostop breathing, and this is normal if itdoes not cause a disturbance of yourhealth, but it will be a disease if it


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causes something, in these newbornpremature they have sleeping apnea, whichstops gas exchange, increase the CO2, whenit reaches to the point where itstimulates the chemical receptors in thebrain it will cause the hyperventilationor cause you to wake up and breathnormally "this is in our situation normalone",

But if that level of CO2 does not affectthe centers because of prematurity in thatnewborn it will reach 70ml hg of CO2without waking up the centers, so itcauses a depression of respiratory centersinstead of stopping the apnea you godeeper in it without shouting without

crying without moving until therespiratory system is dead and the baby isdead :'(

So this is the last thing that you shouldknow for the exam, study well, the doctorhopes he has done good. Sorry for beinglate and sorry for any mistake .

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I believe in you NeRDzZz

Your sister: nada nammas.

Physiology, Lecture 7, Gas Transport (Lecture Notes)

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