Gas Transport and Respiratory Control - L5

Question 1

oxygen transport is in 2 forms what are they and their %?

Answer 1

a)1.5 % Dissolved in plasma
So, 3 mlO2.litre-1blood (0.3 mlO2.dl-1) dissolved in plasma
NB: Only dissolved gas contributes to circulating partial pressures
b) 98.5 % Bound to haemoglobin
* Hb binds 1.34 ml O2.g-1 (x 130 – 150 g.litre-1 )
* Provides 175 – 200 ml O2.litre-1blood (17.5 – 20 ml O2.dl-1)

Question 2

where is Hb - Haemoglobin found?

Answer 2

only in RBCs

Question 3

g.litre ^-1 of Hb in men and women?

Answer 3

150 g.litre-1 in men (15 g.dl-1)
130 g.litre-1 in women (13 g.dl-1)

Question 4

Structure of Hb?

Answer 4

Tetrameric globular protein
4 Haem groups (each contain 1 Fe2+ ion)

Question 5

Hoe much O2 does Hb move?

Answer 5

Transports 98.5% of O2 in blood

Question 6

What function does Hb provide?

Answer 6

Greater oxygen carrying capacity

Question 7

What does the co-operative reversible binding of Hb go up to? in terms of O2+CO2 molecules

Answer 7

4 O2 molecules (haem groups)
4 CO2 molecules (globin portion, normally 2 at most in venous blood)

Question 8

Does Hb change affinity and for who?

Answer 8

Yes Hb changes affinity for O2

Question 9

3 Forms of CO2 transport? and %

Answer 9

1. Dissolved - 10%
2. Bound to hg - 30%
3. Bicarbonate (HCO3) - 60% – Mostly in plasma

Question 10

Dissociation curve of Hb and O2?

Answer 10

NOT Linear

Answer 11

When arterial blood is 100 and the 95% of O2 is taken by Hb - most of Hb sites takes by O2
veins have a PO2 of 40 on average and saturation of O2 of Hb with veins is 75% even when CO2 drops - gives us a safety zone of O2

Question 12

What happens the more O2 is bound to Hb?

Answer 12

the more O2 bound to Hb the easier it gets to bind to new O2 molecules

Question 13

What can we not have a PO2 level of?

Answer 13

cannot have a PO2 level of 760 mm Hg

Question 14

PO2 levels when metabolism higher?

Answer 14

PO2 levels in vein is higher

Question 15

Can you change the dissociation curve of Hb for O2?

Answer 15

YES due to many factors

Question 16

What happens if this Hb for O2 curve is shifted to the right? Main thing + 3 things

Answer 16

Tissue level unloading: easier to get rid of O2
1. Increased PCO2 Hb + CO2<-> HbCO2 (Eq right)
2. Decreased pH (­ increase H+)
Hb + O2 Hb <->O2 + H+ (Eq left)
3. Increased Temperature and changes conformation of Hb so it is easier to unload Hb from O2

Question 17

What happens left side of curve?

Answer 17

Left shifted
* Lung level loading – ¯ PCO2
– ­ pH (¯ H+)
– ¯ Temperature
easier to load on O2 to Hb

Question 18

what is the metabolite made in produced of RBC? when is it signficant?

Answer 18

when O2 levels are low at high altitude and this induces a change in Hb so it is easier to unload O2 from Hb in tissue
2,3-diphosphoglycerate
- 2,3-DPG → right shift
- Metabolite of rbc glycolysis
- Significant in hypoxia (altitude)
- At lungs: promotes unloading

Question 19

4 types of hypoxia

Answer 19

Hypoxic hypoxia, anaemic hypoxia, circulatory hypoxia and histotoxic hypoxia

Question 20

what is hypoxia?

Answer 20

insufficient cellular O2 - low levels of oxygen in the blood

Question 21

exam + mqs

Answer 21

follow numbers from slide 7 yellow box

Question 22

What is the Chloride shift?

Answer 22

Cl ions moved into RBCs and hydrogen carbonate shifted out and this is how most of CO2 are carried out

Question 23

Hypoxic Hypoxia?

Answer 23

Arterial PO2 levels are low due to high altitude
Lots of O2 sites are not taken on Hb as Hb is not taken by O2 such as when staurtion drops below 70%
Low PaO2 (hypoxemia) → ↓ %Hb Sat – Inadequate gas exchange
– ↓ PB (altitude)
– Cyanosis (skin bluish tint) = <70% Hb Sat

Question 24

Anaemic hypoxia?

Answer 24

Arterial O2 levels can be normal but not enough Hb: ↓ total blood O2 content with normal PaO2
can be induced by ingesting Carbon monoxide as CO has a higher affinity (24 times) for Hb than O2 - so it takes all the sites
receptors don’t detect how much Hb is bound by O2 - silent killer

– ↓ circulating rbc’s; ↓ rbc Hb content
– CO poisoning (no cyanosis – HbCO is pink, pale skin)
* CO: 24 times more affinity with Hb than O2.

Question 25

Circulatory hypoxia?

Answer 25

O2 and Hb content normal but there's a blockage so O2 cannot get into cells ↓ supply of oxygenated blood with normal O2 content and PaO2 – Vessel blockage, congestive heart failure

Question 26

What pathology is associated with circulatory hypoxia?

Answer 26

Congestive heart failure

Question 27

Histotoxic hypoxia?

Answer 27

* O2 delivery to tissues normal, but cells unable to use it. – Cyanide is an example poisoning (cyanide blocks essential enzymes for cellular respiration) and prevent from getting O2 needed in cells some cellular mechanisms do not work properly

Question 28

What is hyperoxia?

Answer 28

Too much O2 in cells - i.e. O2 toxicity - above normal arterial O2

Question 29

Disease Hyperoxia?

Answer 29

(when ↓PaO2 arterial O2): * can improve gradient but can be dangerous as an ­O2 can damage brain (could cause blindness) * when O2 is the main driver of ventilation: ­O2 can increase the risk of ↓ peripheral chemoreceptor sensitivity

Question 30

can too much O2 be fatal?

Answer 30

YES - can damage brain and rest of body

Question 31

When O2 levels are very low what happens?

Answer 31

Becomes main driver of ventilation control and so when CO2 comes in it can mess up this control

Question 32

Is there a big effect of Hyperoxia in a healthy person?

Answer 32

no big effect (Hb saturation almost to the max)

Question 33

What is hypercapnia?

Answer 33

Too much CO2 in arterial blood

Question 34

What is hypocapnia

Answer 34

Not enough CO2 in arterial blood

Question 35

Cause of hypocapnia?

Answer 35

Via hyperventilation - over breathing - taking more O2 then needed and losing too much CO2

Question 36

How does hypercapnia occur?

Answer 36

Via hypoventilation - under breathing

Question 37

When does hypercapnia occur and what does it occur in conjuction in ?

Answer 37

Occurs with most lung diseases Occurs in conjunction with reduced PaO2

Question 38

When does hypocapnia occur with?

Answer 38

Occurs with anxiety and fear

Question 39

Is there an impact on arterial O2: PAO2 with hypocapnia? is there an exception?

Answer 39

No impact on PaO2 - Except at low PB (e.g. altitude) where low PaO2 stimulates a hyperventilation

Question 40

What is Hyperpnea?

Answer 40

Increased breathing/ventilation to match metabolic demand (e.g. exercise)

Question 41

What is ventilation controlled by?

Answer 41

Chemoreceptors

Question 42

What 2 chemoreceptors control ventilation?

Answer 42

Peripheral and central

Question 43

Where and are the respiratory controls in the brain?

Answer 43

Pons and Medulla respiratory controls Pons - Pneumoatix and Apneustic centres Medulla - Dorsal and Ventral respiratory group

Question 44

What does the medulla respiratory control activate and when?

Answer 44

dorsal activates respiratory muscles ventral activated when breathing is more active such as active breathing in exercise when abdominal muscles are being used

Question 45

Hering-Breur reflex - Pulmonary stre

Answer 45

prevents an over inflation of lungs when Tv is below 1L they promote a reduction to regulate

Question 46

what do irritant receptors do?

Answer 46

Irritants receptors - dust and pollutants they trigger coughing or sneezing when needed

Question 47

Proprioceptors?

Answer 47

Joints Evidence that they influence breathing during exercise just by flexing some muscles you can indcue some increase in ventilation

Question 48

Where are peripheral chemoreceptors located?

Answer 48

change to change in arterial PO2 substantitaly not when it just drops slightly they provide about 20% of respiratory drive some studies show that these receptoprs might detect Hb content howver it is up for debate rarely there is evidnce that they can detect total arterial content - how much Hb is bound to O2 and this is important for anaemia and CO poisoning etc

Question 49

Where are central chemoreceptors located?

Answer 49

Medulla in brain

Question 50

Can H^+ions cross the BBB? What is the importance of this?

Answer 50

important than H^+ions cannot cross BBB CO2 reacts with H20 -> carbon

Question 51

Function of central chemoreceptors?

Answer 51

they don't react to changes in O2 levels - it is to Hydrogen ions so they indirectly respond to arterial pressure of CO2

Question 52

% respiratory drive of central chemoreceptors?

Answer 52

80% of respiratory drive

Question 53

cnetral chemorecpetors for control of cO2 in body what do they do?

Answer 53

when co2levels icnrease to a toxic level instead of stimulating the rsportaory centre they depress it must not icnrease levels to a toxic way above 80/90 then they start inhibiting

Question 54

What is the effects of arterial O2 on ventilation? due to CO2/O2 levels

Answer 54

* Not much of a change until PO2 £ 60 mm Hg * Response due to activation of peripheral chemoreceptors only (assuming no changes in PCO2 or pH are also occurring) - small drop in O2 not really detected

Question 55

when co2 levels are toxic?

Answer 55

can lose consciousness

Question 56

What is the effect of hypoventilation on minute ventilation: VE?

Answer 56

Negative feedback arterial co2 increase and arterial oxygen decrease and hydrogen ions go up chemoreceptors detect and respond resiratory control centre increases ventilation

Question 57

What is the effect of hyperventilation on minute ventilation: VE?

Answer 57

negative feedback decrease of co2 in blood and decrease of hydrogen ions with an increase in arterial o2 in blood, chemoreceptors detect and respond and the respiratory control centre causes a decrease in ventilation

Question 58

Perspective

Answer 58

potentially carotid infection might be responsible for siolent Hypoxemia in COVID 19 patients