Lecture 14- Respiratory 2

Question 1

What is Tidal volume? (TV)

Answer 1

the amount that goes in and out= usually small percentage of the breath potential -difference between the inspiration and expiration -can vary enormously depending on how hard we breath in, can be small in rest and big in exercise

Question 2

What is Inspiratory capacity? (IC)

Answer 2

big breath in

Question 3

What is inspiratory reserve volume? (IRV)

Answer 3

-the volume we could be using if we took a huge breath in -The maximum amount of air that can be breathed in during a deep inspiration.

Question 4

What is expiratory reserve volume? (ERV)

Answer 4

volumes we can get get if expire a lot -the maximum amount of air that can be breathed out during active expiration.

Question 5

What is Vital capacity? (VC)

Answer 5

-the potential breath when breathing maximally -The maximum capacity of the lungs minus the residual volume

Question 6

What is residual volume? (RV)

Answer 6

-some air always stays in the lung this is it even if we breath out a lot -The leftover volume of “dead” air that is left over in the lungs after a forceful expiration

Question 7

What is the functional residual capacity? (FRC)

Answer 7

-the air that stays in during normal breathing -The leftover volume of air after passive expiration

Question 8

What is total lung capacity? (TLC)

Answer 8

-total of the air possible in lungs

Question 9

How do you calculate Pulmonary ventilation (ml/min)?

Answer 9

Pulmonary ventilation (ml/min) = tidal volume (ml/breath) X respiratory rate (breaths/min)

Question 10

How do you calculate tidal volume (TV)?

Answer 10

End-inspiratory vol - end-expiratory vol = tidal volume

Question 11

What is anatomical dead space?

Answer 11

-dead space= the air that is in the upper airways and bronchi, then that isn’t used for diffusion in the alveoli it comes in with the breath and leaves with breathing out Dead-space/tidal volume ratio : -33% in human & dog -50-75% in cattle & horse (resting state) -dead space stays about the same even in exercise but proportionally we will lose less, so bigger breaths= the percentage is smaller but the amount tsays the same

Question 12

Why is dead space important?

Answer 12

-Dead-space ventilation important during exercise, thermoregulation -dead space is important to retain some CO2 which is important for pH maintanance = like in panting! and exercise have to have the dead space so CO2 is maintained

Question 13

What enters the alveoli during inspiration?

Answer 13

combination of fresh air and the air from the previous breath

Question 14

How do you calculate alveolar ventilation?

Answer 14

ssuming quiet breathing at rest: average values Alveolar ventilation = (500 ml/breath) - (150 ml dead space volume) x 12 breaths/min = 4,200 ml/min

Question 15

What happens to Alveolar ventilation with: 1. Deep, slow breathing? 2. Shallow, rapid breathing

Answer 15

1.smaller proportion of dead space so the propotion will increase 2.more dead space so proprtion of the alveolar ventilation to the pulmonary ventilation will be smaller

Question 16

What is perfusion?

Answer 16

perfusion= the flow of air going through

Question 17

What is ventilation?

Answer 17

ventilation= getting the air in

Question 18

How is ventilation and perfusion matched?

Answer 18

when change in ventilation= should affect the circulation around the alveoli so you can take up more O2 and dump more CO2 -Local control of individual airways supplying specific alveoli - Optimizes efficiency of O2 & CO2 exchange -Direction of effect is opposite to that in systemic arterioles (=-the circulation affaected by O2 and CO2 levels, normally low 02 leads to vasodilation= more flow in blood vessels but here! the opposite- vasoconstriction= the reason is that it is matching the uptake of oxygen not the coming in of it) -first point= the smooth muscle around bronchioles can change the diamater and even determine the participation of the alveoli

Question 19

How is airflow and bloodflow regulated in an area in which blood flow (perfusion) is greater than airflow (ventilation)?

Answer 19

Question 20

How is airflow and bloodflow regulated in an area in which airflow (ventilation) is greater than blood flow (perfusion)?

Answer 20

Question 21

What partial pressure do the gasses in air and water (blood) sum up to?

Answer 21

Mixed gases in air & water (blood) exhibit individual partial pressures that sum to atmospheric pressure 760 mm Hg

• Depends on volume of gas (& solubility in liquid)
• Gases move down partial pressure gradients

Question 22

Explain the exchange of gas due to pressure gradients, in and out of body?

Answer 22

given that at rest and good health the blood coming from the alveoli= about a 100 as well

gets to tissues loses the O2 some of it, drops to 40

then CO2 goes out as the pressure is higher in than out and the reverse with O2

Question 23

What causes the air to leave lungs?

Answer 23

As the external intercostals & diaphragm contract, the lungs expand. The expansion of the lungs causes the pressure in the lungs (and alveoli) to become slightly negative relative to atmospheric pressure. As a result, air moves from an area of higher pressure (the air) to an area of lower pressure (our lungs & alveoli). During expiration, the respiration muscles relax & lung volume descreases. This causes pressure in the lungs (and alveoli) to become slight positive relative to atmospheric pressure. As a result, air leaves the lungs.

Question 24

What is partial pressure?

Answer 24

t’s the individual pressure exerted independently by a particular gas within a mixture of gasses. The air we breath is a mixture of gasses: primarily nitrogen, oxygen, & carbon dioxide. So, the air you blow into a balloon creates pressure that causes the balloon to expand (& this pressure is generated as all the molecules of nitrogen, oxygen, & carbon dioxide move about & collide with the walls of the balloon). However, the total pressure generated by the air is due in part to nitrogen, in part to oxygen, & in part to carbon dioxide. That part of the total pressure generated by oxygen is the ‘partial pressure’ of oxygen, while that generated by carbon dioxide is the ‘partial pressure’ of carbon dioxide. A gas’s partial pressure, therefore, is a measure of how much of that gas is present (e.g., in the blood or alveoli).

the partial pressure exerted by each gas in a mixture equals the total pressure times the fractional composition of the gas in the mixture. So, given that total atmospheric pressure (at sea level) is about 760 mm Hg and, further, that air is about 21% oxygen, then the partial pressure of oxygen in the air is 0.21 times 760 mm Hg or 160 mm Hg.

Question 25

How does the exachange of O2 and CO2 occur between the air and the blood?

Answer 25

The exchange of gases (O2 & CO2) between the alveoli & the blood occurs by simple diffusion: O2 diffusing from the alveoli into the blood & CO2 from the blood into the alveoli. Diffusion requires a concentration gradient. So, the concentration (or pressure) of O2 in the alveoli must be kept at a higher level than in the blood & the concentration (or pressure) of CO2 in the alveoli must be kept at a lower lever than in the blood. We do this, of course, by breathing - continuously bringing fresh air (with lots of O2 & little CO2) into the lungs & the alveoli.

Question 26

How do the external intercostals plus the diaphragm contract to bring about inspiration?

Answer 26

Contraction of external intercostal muscles > elevation of ribs & sternum > increased front- to-back dimension of thoracic cavity > lowers air pressure in lungs > air moves into lungs
Contraction of diaphragm > diaphragm moves downward > increases vertical dimension of thoracic cavity > lowers air pressure in lungs > air moves into lungs:

Question 27

Why is it a problem that the alveoli are coated by water?

Answer 27

The walls of alveoli are coated with a thin film of water & this creates a potential problem. Water molecules, including those on the alveolar walls, are more attracted to each other than to air, and this attraction creates a force called surface tension. This surface tension increases as water molecules come closer together, which is what happens when we exhale & our alveoli become smaller (like air leaving a balloon). Potentially, surface tension could cause alveoli to collapse and, in addition, would make it more difficult to ‘re-expand’ the alveoli (when you inhaled). Both of these would represent serious problems: if alveoli collapsed they’d contain no air & no oxygen to diffuse into the blood &, if ‘re-expansion’ was more difficult, inhalation would be very, very difficult if not impossible. Fortunately, our alveoli do not collapse & inhalation is relatively easy because the lungs produce a substance called surfactant that reduces surface tension.

Question 28

What are the partial pressures of O2 and CO2 in resting condition in the alveoli, alveoli capillaries, and blood?

Answer 28

Alveoli
PO2 = 100 mm Hg
PCO2 = 40 mm Hg

Alveolar capillaries:
Entering the alveolar capillaries
PO2 = 40 mm Hg (relatively low because this blood has just returned from the systemic circulation & has lost much of its oxygen)
PCO2 = 45 mm Hg (relatively high because the blood returning from the systemic circulation has picked up carbon dioxide)

-While in the alveolar capillaries, the diffusion of gasses occurs: oxygen diffuses from the alveoli into the blood & carbon dioxide from the blood into the alveoli.

Leaving the alveolar capillaries:
PO2 = 100 mm Hg
PCO2 = 40 mm Hg

Blood leaving the alveolar capillaries returns to the left atrium & is pumped by the left ventricle into the systemic circulation. This blood travels through arteries & arterioles and into the systemic, or body, capillaries. As blood travels through arteries & arterioles, no gas exchange occurs.

Entering the systemic capillaries:
PO2 = 100 mm Hg
PCO2 = 40 mm Hg

Body cells (resting conditions):
 PO2 = 40 mm Hg
 PCO2 = 45 mm Hg
 Because of the differences in partial pressures of oxygen & carbon dioxide in the systemic capillaries & the body cells, oxygen diffuses from the blood & into the cells, while carbon dioxide diffuses from the cells into the blood.

Leaving the systemic capillaries:
PO2 = 40 mm Hg
PCO2 = 45 mm Hg
Blood leaving the systemic capillaries returns to the heart (right atrium) via venules & veins (and no gas exchange occurs while blood is in venules & veins). This blood is then pumped to the lungs (and the alveolar capillaries) by the right ventricle.

Question 29

Why is alveolar PO2 100 mm Hg when atmospheric PO2 is 160 mm Hg?

Answer 29

At body Temp. PH2O vapour = 47 mm Hg ␣ PO2 150 mm Hg ie. dead-space (functional residual capacity)
␣ O2 is continually moving down its partial pressure gradient ␣ ie across alveoli into blood

-the air coming in is warmed and humidified so has larger vapor content= protection for the alevoli and also the partial pressure of this water is diluting the O2 and the dead space too the reulsting partial pressure= about 100

Question 30

What are the factors influencing gas exchange at the alveolar membrane?

Answer 30

• Partial pressure gradient: Major determinant (PAO2 ␣ PcapO2)=Pcap 02= partial pressure in capillary
• Surface area of alveolar membrane (A) :

Constant at rest, rises during forced inspiration eg during exercise, decreases during some pathophysiological states(the larger the area the better it will be able to flow across also depends on how many alveoli participate= in big breaths =more)

-Thickness of air blood barrier (x):Constant at rest
rises during some pathophysiological states (the thicker it is the slower the movement of oxygen across

when horses go hard. increas ein the intestitial space fluid= so thicker air blood barrier= point where the limit is reached )

-Diffusion coefficient of gas (D )
␣ CO2 : 20x > O2

Rate of O2 movement = D . A . (PAO2 - PcapO2)/x

Question 31

How are oxygen & carbon dioxide transported in the blood?

Answer 31

-Oxygen is carried in blood:

1 - bound to hemoglobin (98.5% of all oxygen in the blood)
2 - dissolved in the plasma (1.5%)

Carbon dioxide - transported from the body cells back to the lungs as:

1 - bicarbonate (HCO3) - 60%
formed when CO2 (released by cells making ATP) combines with H2O (due to the enzyme in red blood cells called carbonic anhydrase) as shown in the diagram below
2 - carbaminohemoglobin - 30%
formed when CO2 combines with hemoglobin (hemoglobin molecules that have given up their oxygen)
3 - dissolved in the plasma - 10%

Question 32

What is Hemoglobin saturation?

Answer 32

extent to which the hemoglobin in blood is combined with O2
depends on PO2 of the blood:

Question 33

Explain the oxygen-haemoglobin dissociation curve

Answer 33

at high partial pressures of O2 (above about 40 mm Hg), hemoglobin saturation remains rather high (typically about 75 - 80%). This rather flat section of the oxygen-hemoglobin dissociation curve is called the ‘plateau.’

Recall that 40 mm Hg is the typical partial pressure of oxygen in the cells of the body. Examination of the oxygen-hemoglobin dissociation curve reveals that, under resting conditions, only about 20 - 25% of hemoglobin molecules give up oxygen in the systemic capillaries. This is significant (in other words, the ‘plateau’ is significant) because it means that you have a substantial reserve of oxygen. In other words, if you become more active, & your cells need more oxygen, the blood (hemoglobin molecules) has lots of oxygen to provide

When you do become more active, partial pressures of oxygen in your (active) cells may drop well below 40 mm Hg. A look at the oxygen-hemoglobin dissociation curve reveals that as oxygen levels decline, hemoglobin saturation also declines - and declines precipitously. This means that the blood (hemoglobin) ‘unloads’ lots of oxygen to active cells - cells that, of course, need more oxygen.

Question 34

What Factors affect the Oxygen-Hemoglobin Dissociation Curve?

Answer 34

• lower pH
• increased temperature
• more 2,3-diphosphoglycerate
• increased levels of CO2

These factors change when tissues become more active. For example, when a skeletal muscle starts contracting, the cells in that muscle use more oxygen, make more ATP, & produce more waste products (CO2). Making more ATP means releasing more heat; so the temperature in active tissues increases. More CO2 translates into a lower pH. That is so because this reaction occurs when CO2 is released:
CO2 + H20 —–> H2CO3 —–> HCO3- + H+

& more hydrogen ions = a lower (more acidic) pH. So, in active tissues, there are higher levels of CO2, a lower pH, and higher temperatures. In addition, at lower PO2 levels, red blood cells increase production of a substance called 2,3-diphosphoglycerate. These changing conditions (more CO2, lower pH, higher temperature, & more 2,3-diphosphoglycerate) in active tissues cause an alteration in the structure of hemoglobin, which, in turn, causes hemoglobin to give up its oxygen. In other words, in active tissues, more hemoglobin molecules give up their oxygen. Another way of saying this is that the oxygen-hemoglobin dissociation curve ‘shifts to the right’ (as shown with the light blue curve in the graph below). This means that at a given partial pressure of oxygen, the percent saturation for hemoglobin with be lower. For example, in the graph below, extrapolate up to the ‘normal’ curve (green curve) from a PO2 of 40, then over, & the hemoglobin saturation is about 75%. Then, extrapolate up to the ‘right-shifted’ (light blue) curve from a PO2 of 40, then over, & the hemoglobin saturation is about 60%. So, a ‘shift to the right’ in the oxygen-hemoglobin dissociation curve (shown above) means that more oxygen is being released by hemoglobin - just what’s needed by the cells in an active tissue!

Question 35

How does Haemoglobin transport the oxygen?

Answer 35

Haemoglobin forms unstable compound oxyHb

• Disassociates in water
• Blood P drives the reaction left or right O2

-Hb+O2 =HbO2(easy to dissociate not a time bind not that strong)

capacity of plasma is limited in how much O2 it can carry= so it has RBCs full of haemoglobin that can bind to the oxygen and take it out of the solution

Dissolved O2 is directly directly proprtional to the partial pressure of O2

Question 36

Why is CO dangerous?

Answer 36

carbon monoxide will bind to Hb strongly= dangerous, can’t get oxygen if all Hb occupied

Question 37

What affects the dissociation curve (lecture)?

Answer 37

-increase in partial pressur eof O2 the increase in Hb saturation

good that it isn’t a straight line=even a modest rise of partial pressure= rapid filling up of the Hb in the end bit not as much as most are already occupied

• Heme-heme interactions responsible for sigmoid shape of Oxy-Hb curve(special dissociation curve= if structure changed this changes)
• type and sequence of Amino acids in protein chain of each heme subunit= alters O2 binding affinity, responsible for different types of mammalian Hb
• small drop in O2 then release lot of O2 from Hb

= bigger difference in the lower levels as ther emay be danger there

the sigmoid curve is due to the nature of Hb

Question 38

What is meant by cooperativity of binding in the dissociation curve?

Answer 38

so most of the oxygen will be released at the low level when it’s most needed in the active tissues

Question 39

What is the Bohr /Root effect?

Answer 39

what can change the dissociation curve:
chang in pH, increase in CO2 (tissues workinh hard more CO2 and increase in hydrogen ion= drop in pH and increase in temperature, biposphogylcerate increase)

moving it to the right= so the steeper part comes earlier= so it will give more oxygen at lower levels still!
around 20% difference in how much O2 delivered to the tissues that need it

Question 40

How are the Differences in shape of OxyHb curve between species measured?

Answer 40

• y measuring PO2 at 50% Hb saturation
• different species have different Hb structures tha affect how the curve looks like
• rabbit= more to the right, then gives out more O2 at lower level= smaller then have metabolic rate higher so need more O2 then larger animals who have lower metabolic rate

Question 41

How is fetal haemoglobin different and why?

Answer 41

• hanged structure of fetal haemoglobin enhances binding affinity for O2
• fetal to the left, fetal haemoglobin hungruer for oxygen so oxygen is taken up from the maternal blood to the fetal

cocn of Hb in fetal blood is higher and PCV is higher so more O2 taken up