Respiration: Gas Exchange

Front 1

composition of air

Back 1

N2: 78.1%
O2: 20.9%
argon: 0.9% inert gas
CO2: 0.03%

Front 2

carbon dioxide

Back 2

3/10,000 molecules
- within last 50 years, [CO2] increased >25%

Front 3

methane

Back 3

- lower [] than CO2
- main sources: volcanoes, cattle

Front 4

partial P of atmospheric gases at sea level

Back 4

N2+ inert gases: 79.1%, 601
O2: 20.9%, 159
CO2: 0.03%, 0.23
- total 760 mmHg

Front 5

partial P of water

Back 5

- maximum depends of T:
1. warm air can hold more: 0 celsius/ 5, 100 celsius/ 760
2. availability of H2O
- in animal: air is constantly humidified to a max of 47 at 37 celsius

Front 6

Law of Henry

Back 6

concentration of dissolved gas (Cx)= Partial P (Px) x Solubility Coefficient (alpha x)

Front 7

diffusion of gases in alveoli

Back 7

- gases of respiratory importance are highly soluble in lipids and cell mem
- major limitation: diffusion through tissue water
- CO2 is 20x more soluble than O2

Front 8

normal control of oxygen concentration

Back 8

- 75kg: 4.2 L air/ min to get 250ml O2 required by metabolism
- respiration controlled by respiratory center in the medulla oblongata
- maintains PP O2 at 104 mmHg

Front 9

voluntary hyperventilation and oxygen concentration

Back 9

voluntary hyperventilation
- increase in ventilatory rate increases PO2 in alveoli
- at very high rates: PO2 alveoli comes close to max 149mm Hg (theoretically would be 159mm Hg, but alveolar vapor reduces P)

Front 10

normal control of CO2 concentration

Back 10

- controlled similarly to oxygen: respiratory center maintains PP CO2 at 40mmHg
- via adjusting respiratory rate
- at rest 75kg: expires 200ml CO2 produced by metabolism

Front 11

increased metabolism and [O2] alveoli

Back 11

- requires more O2
- at consumption 1000ml/min: maintain PO2 of 104mmHg, increase ventilation to ~18L/min

Front 12

increased in respiratory rate and [CO2] alveoli

Back 12

- decreases PCO2 in alveoli
- theoretical min of 0mmHg can never be achieved

Front 13

increased metabolism and [CO2] alveoli

Back 13

- CO2 production increases
- to maintain normal alveolar P at 40:
increase ventilation rate
- eg 800ml CO2/ min: respiratory rate ~18 L/min

Front 14

dead space vs ambient air

Back 14

- first air inspired is first air expired on next expiration
- volume doesn't reach the alveoli, but remains in dead space
- only difference w/ ambient: dead space air is saturated with vapor

Front 15

first expired air vs ambient air

Back 15

- PO2 and PCO2 in first air = 1/2 value of saturated ambient air
- PO2= 149, PCO2= 0.23

Front 16

mixture of dead space and alveolar air

Back 16

- PO2 and PCO2 change from dead space to alveolar values:
1. O2: 149 to 104
2. CO2: 0.23 to 40

Front 17

pure alveolar air

Back 17

PO2: 104
PCO2: 40

Front 18

inspiration and alveolar air

Back 18

1. first volume of air is that remaining in the dead space from the previous expiration
2. decreases in PO2 and increase in PCO2 fresh air follows
3. increase in PO2 and decrease in PO2

Front 19

expiration and alveolar air

Back 19

- no fresh air is added
- decrease in PO2 and increase in PCO2

Front 20

exercise and alveolar air

Back 20

increased metabolism causes steeper changes in PO2 and PCO2