respiratory 23

Question 1

what are the 2 ways in which oxygen is transported in the blood?

Answer 1

-bound to haemoglobin( major way)
-dissolves in solution( plasma)

Question 2

haemoglobin structure

Answer 2

Hemoglobin: polypeptide, alpha & beta chains. 4 binding sites within the hemoglobin molecule: haem moiety( Iron ions).
To each haem moiety 1 molecule of O2 can bind. .

Question 3

Allosteric effect

Answer 3

The speed with which O2 molecules are loaded onto haemoglobin: 4th>3th>2nd>1st

Allosteric effect: when the 1st molecule of O2 binds it turns the haemoglobin molecule to expose the next haem moiety. Same happens with the next O2 molecules. The more molecules are taken up the faster it is. Co-operative binding property.

Question 4

what is the difference in % of saturation of haemoglobin between systemic veins and systemic arteries.

Answer 4

25%

Question 5

why is haemoglobin saturation decreased at lower PO2?

Answer 5

Haemoglobin loses affinity for O2 at lower PO2.
It releases O2 at lower PO2 in the tissues.
This change in affinity is key for delivering/releasing O2 to the tissues.
At tissues – more CO2, lower pH, so O2 is released

Question 6

why is haemoglobin saturation higher in the lungs?

Answer 6

increased affinity for O2. encourages O2 uptake in the lung
At lungs – less CO2, higher pH, so O2 is taken up

Question 7

what is the saturation of haemoglobin if the person has lost half of their blood?

Answer 7

still 100%. Haemoglobin molecule is not affected

Question 8

what factors reduce the affinity of haemoglobin for oxygen?

Answer 8

increased CO2, [H+], temperature, DPG

Question 9

What factors increase the affinity of haemoglobin for oxygen?

Answer 9

Decreased CO2, [H+], temperature, DPG
Increased CO

Question 10

Bohr shift

Answer 10

the shift to the right of the oxygen equilibrium curve of both adult and fetal blood in response to an increase in PCO2 or a decrease in pH, or both.
For a given PO2 more oxygen is released

Question 11

what is the importance of fetal haemoglobin having a higher affinity for O2 than adult haemoglobin?

Answer 11

otherwise would not be able to draw blood from mother’s circulation

Question 12

Why does haemoglobin loose its affinity for O2 at lower PO2?

Answer 12

-decreased in pH
In an acidic environment, Hb has less affinity for O2.
At tissues- more CO2, lower pH, so O2 is released
At lungs- less CO2, higher pH, so O2 is taken up

Question 13

The Haldane effect

Answer 13

physicochemical phenomenon which describes the increased capacity of blood to carry CO2 under conditions of decreased haemoglobin oxygen saturation
Greater affinity for CO2 in the tissues

Question 14

Myoglobin function

Answer 14

stores O2 around skeletal muscle where it can be later released in conditions of low CO2
Has very high affinity for O2

Question 15

why is the oxygen saturation curve sigmoidal?

Answer 15

due to cooperative binding

Question 16

what is hemoglobin called when its a 100% saturated?

Answer 16

Oxyhaemoglobin

Question 17

what is the rate-limiting step of the formation of HCO3-?

Answer 17

formation of H2CO3 from H2O and CO2

Question 18

what is the main way of carrying CO2 in the body?

Answer 18

in the form of bicarbonate that was rapidly formed in RBC and diffused into the plasma 60%
+ 20% of rapidly formed bicarbonate stayed in RBC

Question 19

how much of CO2 is carried in plasma?

Answer 19

70%

Question 20

how much CO2 is carried in RBC?

Answer 20

30%

Question 21

what are the ways in which CO2 can be transported in blood?

Answer 21

Question 22

rwhat is the enzyme that catalyzes the formation of H2CO3 in RBC?

Answer 22

carbonic anhydrase

Question 23

what dictates which way this process goes?

Answer 23

Law of Mass action

Question 24

Law of Mass action

Answer 24

law of mass action, law stating that the rate of any chemical reaction is proportional to the product of the masses of the reacting substances

Question 25

describe the chemical basis of CO2 release of O2 uptake in the alveoli

Answer 25

-CO2 dissociates from the carbamino compound-> diffuses out of the RBC into plasma and into alveoli

-Haemoglobin gains affinity for O2. O2 diffuses from the alveoli into plasma and into RBC-> binds with haemoglobin

-HCO3- diffuses back into RBC from plasma. Carbonic anhydride and H+ combine to form carbonic acid(H2CO3)

-Carbonic acid(H2CO3) dissociates back into CO2 and H2O.
H2O and CO2 diffuse out of RBC into plasma. CO2 diffuses out into alvoli.

-Chloride shift reversed

Question 26

where are peripheral chemoreceptors located

Answer 26

near major blood vessels

In the Carotid body( located at the bifurcation of the common carotid artery in the neck. Between where the internal and external carotid arteries originate. (Close to baroreceptors in the wall of
Carotid sinus. ) Connected by the sinus nerve, which joins the glossopharyngeal
nerve( 9th cranial nerve) then to the medulla oblongata(brainstem)

Question 27

where are central chemoreceptors located?

Answer 27

within medulla oblongata

Question 28

what stimulates peripheral chemoreceptors?

Answer 28

Question 29

what is the role of peripheral chemoreceptors?

Answer 29

Peripheral chemoreceptors monitor changes in arterial blood O2, and within seconds after the onset of hypoxia they trigger cardiorespiratory changes (i.e., increase in breathing and blood pressure), which are important for maintaining O2 homeostasis

Question 30

what stimulates central chemoreceptors?

Answer 30

H+ ions in CSF predominantly stimulate Central chemoreceptors.

These come from the dissociation of H2CO3 into HCO3- and H+

Neural cells in the medulla become activated and stimulate breathing

Brain is intrinsically sensitive to H+ ions

DOES NOT RESPOND TO LOW O2(hypoxia) ONLY TO HIGH H+ from evelated CO2

Question 31

why are central chemoreceptors slow to respond?

Answer 31

H+ cannot exit the blood
Vessels as they are charged, but CO2 can

Takes time for this process to occur

+ limted carbonic anhydrase in CSF

~30 sec

Question 32

what is the ventilatory response to hypoxia?

Answer 32

As PaO2 decreases min. ventilation increases. After persistent hypoxia ventilation slows due to central depressant effect within the brainstem(important respiratory neurons in the brainstem are depressed by prolonged hypoxia)-> apnoea-> individual will gasp as the last attempt to auto-ressucitate

PERIPHERAL CHEMORECEPTORS ONLY!

Question 33

what is referred to as the dog leg relationship?

Answer 33

ventilatory response to hypercapnia( high CO2)

Very sensitive to CO2

As PCO2 increases the ventilation rate increases sharply

central chemoreceptors ~80%
peripheral chemoreceptors ~20%

Question 34

what is Ondine’s curse?

Answer 34

No central chemoreceptors and you can die in your sleep. Related to a missing transcription factor.