Gas transport and respiratory control

Question 1

Two forms of O2 that blood carries

Answer 1

• Dissolved O2
• Bound to
  Haemoglobin in RBCs

Question 2

How much O2 in blood at physiological pH

Answer 2

Due to solubility of O2 in blood at physiological PP, Only about 3 mL of O2 per litre of blood, so
about 15 mL total

Question 3

1º molecule for O2 binding

Answer 3

Haemoglobin, O2 binds to haem

Question 4

How does Haemoglobin help with O2 binding?

Answer 4

O2 diffuses from alveoli to pulm –> binds to Haem –> O2 PP decreases so more O2 diffuses and binds to Haem until all binding sites of Haemoglobin have been saturated

Question 5

What causes the sigmoidal curve

Answer 5

The conformational change of Haem, causes the O2 binding to become easier

Question 6

What is p50

Answer 6

Measures the efficacy of O2 binding to Haem i.e if you need to ^ the PP to force binding to Haem, the p50 ^

Question 7

Upper flat part of the curve

Answer 7

moderate changes in PO2
around the normal value (~100
mmHg) have only small effects
on the % saturation and
therefore the amount of O2
carried by arterial blood
i.e some reserve capacity.

Question 8

Steep part of curve at lower
PO2

Answer 8

helps with loading of Hb in
lungs AND unloading of O2 to
the tissues.
Small changes in PO2 result in
large changes in amount of O2
bound to haemoglobin

Question 9

What causes the constant shifting of the curve?

Answer 9

-temperature - high tem lower affinity
- ^PCO2 - offload O2 as it can change our pH levels
-^ in metabolic by product results in reduction of attraction between Haemoglobin and O2

Question 10

How does Haemoglobin offload O2

Answer 10

When the haemoglobin encounters working tissue, metabolic products of CO2 (releases H+ ions which ^ acidity). + ^ temp due to working tissue causes the Haemoglobin to offload the O2 bound to it

Question 11

3 forms of transported CO2

Answer 11

1. Dissolved in plasma - 20 times more soluble than
   O2 (~7%)
2. As bicarbonate (70%)
3. Combined with proteins as carbamino compounds
   (23%) [bound to globin component]

Question 12

How does CO2 dissolve in H20

Answer 12

Goes through the RBC –> 70% gets converted by carbonic anhydrase

Question 13

How is bicarbonate formed?

Answer 13

Carbonic acid made by RBC immediately dissociated to form Bicarbonate and H+ ions

Question 14

What happens to the HCO3- ions

Answer 14

They move out of the RBC down their conc. grad

Question 15

What is chloride shift?

Answer 15

The Cl- ions move into RBC when HCO3- moves out to maintain neutrality

Question 16

How is CO2 removed from the body

Answer 16

• Dissolved CO2 diffuses across the mem to alveoli due to PP grad, reduced the PP of plasma
• Drives CO2 movement from RBC to plasma –> HCO3- reenters and combines with H+ in a red reaction (H20 + CO2) produced and the CO2 diffuses and is expelled

Question 17

What happens to the haemoglobin after offloading CO2

Answer 17

binds to O2 due to ^ affinity

Question 18

What is involuntary breathing controlled by?

Answer 18

The medulla oblongata in the brainstem

Question 19

What happens during exercise (to neurons)

Answer 19

Diff pops of neurons are innervated during breathing

• During exercise, more neurons from med + pons are innervated

Question 20

Central controller of breathing is located in …

Answer 20

The medulla

Question 21

What are the central chemoreceptors sensitive to

Answer 21

Changes in PCO2

Question 22

How do central chemoreceptors control the PCO2 levels

Answer 22

• PCO2 ^ when excess CO2 moves across BBB and into CSF, binds to H2O –> HCO3- + H+ –> change in pH triggers chemoreceptors

Question 23

Peripheral chemoreceptors

Answer 23

• Located in the carotid and
  aortic bodies
• Mainly respond to changes
  in arterial PO2
• Limited response to changes
  in PCO2
• Rapidly responding

Question 24

How do stretch receptors control lung size

Answer 24

As the lungs inflate or
deflate, they send afferent
input from stretch receptors
* The brain then sends
efferent output preventing
them from stretching too far