L10.2 Gas Transport and Exchange

Question 1

gas exchange between:

• ? & ?
• ? & ?

Answer 1

gas exchange between:

• alveoli & pulmonary capillaries
• systemic capillaries & tissue cells

Question 2

gas exchange occurs ___ the pressure gradient

Answer 2

gas exchange occurs DOWN the pressure gradient

high pressure -> low pressure

Question 3

what is partial pressures?

Answer 3

the total pressure of a mixed gas is the sum of the partial pressures from each gas
partial pressure: % of total pressure caused by one gas type

Question 4

what is alveolar partial pressures?

Answer 4

composition of air in alveoli is different to atmosphere: alveolar air is mixed with water vapour and CO2; both reduce partial pressure of alveolar O2

Question 5

describe the gas exchange at the lungs

Answer 5

partial pressure gradients:
- O2 diffusion from alveoli to capillaries
- CO2 diffusion from capillaries to alveoli
(see notes for indepth description)

Question 6

what are haemoglobin

Answer 6

• found only in red blood cells
• two parts: globin (protein- four subunits); haeme (non-protein- four haeme groups; iron containing; each iron atom binds one O2 module)
• one haemoglobin molecule binds four O2
• one RBC contains 250 million haemoglobin molecules

Question 7

describe the oxygen bound to haemoglobin

Answer 7

• O2 binding is reversible (Hb + O2 HbO2)
• without O2 binding = deoxyhaemoglobin
• with O2 binding = oxyhaemoglobin
  (see notes for O2 haemoglobin dissociation curve)

Question 8

what is the bohr effect?

Answer 8

CO2 and H+ bind to protein part of haemoglobin and change shape of haemoglobin. This decreases O2 affinity.

Question 9

what are factors affecting O2 binding?

Answer 9

increase CO2, increase H+ concentration or increase warmth of tissue = will encourage the oxygen to come away from the haemoglobin

Question 10

what ways can CO2 be transported in blood?

Answer 10

1. dissolved in blood
2. bound to haemoglobin: globin portion; forms carbamino haemoglobin (HbCO2)
3. as bicarbonate ion (HCO3) (most common)

Question 11

what factors controls breathing?

Answer 11

1. maintaining the rhythm of breathing (inspiration-expiration)
2. regulating rate and depth of breathing (matching breathing to body needs)
3. modifying respiratory activity (e.g. speech, cough)

Question 12

describe the respiratory control centres

Answer 12

• breathing is controlled through respiratory control centres (brain stem- medulla and pons)
• medullary centres: quiet breathing, forced breathing, respiratory breathing
• pons centres: smooth transition between inspiration and expiration

Question 13

describe the medullary control centres

Answer 13

the rate and rhythm of breathing is controlled by the medullary control centres

• dorsal respiratory group (DRG): inspiratory neurons, contraction of inspiratory muscles, quiet breathing
• ventral respiratory group (VRG): inspiratory and expiratory neurons, contraction of inspiratory and expiratory muscles, forced breathing
• pre-botzinger complex: autorhythmic cells, control rate of DRG inspiratory neurons