Alveolar ventilation

Question 1

minute ventilation

Answer 1

tidal volume x respiratory rate

Question 2

conducting airways volume

Answer 2

150ml

Question 3

anatomical dead space

Answer 3

500ml flows into alveoli, but 150ml of it is air from the airways that wasn’t exhaled. moved in and out of airways
don’t allow gas exchange with blood

Question 4

alveolar ventilation

Answer 4

total volume of fresh air entering alveoli per minute - more important in gas exchange

Question 5

factors affecting alveolar ventilation

Answer 5

increasing depth of breathing more effective in increasing alveolar ventilation than increasing rate
taking short, shallow breaths decreases alveolar ventilation because the anatomical dead space ventilation is increased, so no fresh air flows in
fixed volume goes to dead space
if tidal volume decreases, fraction of tidal volume going to dead space increases

Question 6

alveolar dead space

Answer 6

alveoli with little or no blood supply are unable to perform gas exchange, so some fresh air isn’t used

Question 7

physiological dead space

Answer 7

sum of alveolar and anatomical dead spaces

Question 8

rates of gas exchange

Answer 8

rate at which oxygen enters body cells and leaves tissue capillaries is equal to volume of oxygen added to blood in the lungs in same time
rate at which carbon dioxide is produced by cells and enters systemic blood is same as rate of removal and expiration

Question 9

what does balance of oxygen consumed and carbon dioxide produced depend on?

Answer 9

nutrients used for energy - enzymatic pathways for metabolising carbohydrates, fats and proteins generate different amounts of co2

Question 10

respiratory quotient

Answer 10

ratio of co2 produced to o2 consumed

Question 11

respiratory quotients for diff. things

Answer 11

carbohydrates - 1
fat - 0.7
protein - 0.8

Question 12

respiratory quotient for mixed diet

Answer 12

0.8 - 8 molecules of co2 produced per 10 molecules of oxygen consumed

Question 13

% oxygen in atmospheric air

Answer 13

21

79 nitrogen

Question 14

partial pressure of gases

Answer 14

rapidly moving gas molecules collide and exert pressure - increased by increased temp and conc.
independent of pressure other gases exert (Dalton’s law) - molecules os far apart they don’t affect eachother

Question 15

diffusion

Answer 15

from high partial pressure to low

Question 16

total pressure

Answer 16

sum of partial pressures - atmospheric pressure is 760 mmHg

Question 17

Henry’s law

Answer 17

when a liquid is exposed to air containing a gas, molecules of gas will enter liquid and dissolve in it
amount of gas dissolved is directly proportional to the partial pressure of the gas with which liquid is in equilibrium
at equilibrium, partial pressures of gas molecules in liquid and gaseous phases must be identical

Question 18

concentration and solubility

Answer 18

conc of a gas in liquid is proportional to partial pressure and solubility
more solubility -> greater conc at any partial pressure
partial pressures will be same at equilibrium, but concs differ

Question 19

what determines systemic arterial partial pressures?

Answer 19

alveolar partial pressures

Question 20

typical alveolar gas pressures

Answer 20

Po2 = 105 mmHg
Pco2 = 40 mmHg

Question 21

nitrogen in alveoli

Answer 21

biologically inert under normal conditions
doesn’t undergo net exchange
most abundant gas in alveoli

Question 22

typical atmospheric gas pressures

Answer 22

Po2 = 160 mmHg
Pco2 = 0.3 mmHg

Question 23

why are alveolar and atmospheric pressures different?

Answer 23

oxygen is lower in alveoli because some oxygen leaves alveoli to enter pulmonary capillaries
carbon dioxide is higher in alveoli because some oxygen enters alveoli from pulmonary capillaries

Question 24

factors determining alveolar Po2

Answer 24

Po2 of atmospheric air
rate of alveolar ventilation
rate of total-body oxygen consumption

Question 25

effects of factors determining alveolar Po2

Answer 25

decrease of Po2 in atmospheric air decreases alveolar Po2
decrease in alveolar ventilation decreases alveolar Po2
increased consumption of O2 by cells decreases Po2 in blood returning to the lungs - increases conc gradient from lungs to pulmonary capillaries - increases diffusion rate. if alveolar ventilation doesn’t change, alveolar Po2 is reduced, as more fresh air leaves alveoli to enter tissues

Question 26

effects of factors determining alveolar Pco2

Answer 26

decreased alveolar ventilation increases alveolar Pco2]

increased production of co2 increases alveolar Pco2

Question 27

determinants of alveolar Po2 and Pco2

Answer 27

ratio of oxygen consumption to alveolar ventilation - higher the ratio, lower alveolar Po2
ratio of carbon dioxide production to alveolar ventilation - higher the ration, higher alveolar Pco2

Question 28

hypoventilation

Answer 28

occurs in increased ratio of co2 production to alveolar ventilation - can’t keep pace. Pco2 increases

Question 29

hyperventilation

Answer 29

occurs in decreased ratio of co2 production to alveolar ventilation - Pco2 decreases
increased ventilation relative to metabolism

Question 30

partial pressures in systemic venous blood

Answer 30

Pco2 46mmHg
Po2 40mmHg
difference in partial pressures in alveolar-capillary membrane -> net diffusion of oxygen from alveoli to blood and carbon dioxide from blood to alveoli

Question 31

when does net diffusion of gases cease?

Answer 31

when capilllary partial pressures become equal to alveolar partial pressures

Question 32

rates of diffusion in a healthy person

Answer 32

high enough and blood flow slow enough that complete equilibrium is reached before blood reaches the end of capillaries

Question 33

pulmonary circulation at rest vs exercise

Answer 33

capillaries at apex of lung are usually closed due to resting blood pressure being too low to keep them open, but the increased cardiac output in exercise increases pressure and opens them

Question 34

pulmonary edema

Answer 34

filling of alveoli with fluid

increases diffusion barrier

Question 35

diffuse interstitial fibrosis

Answer 35

alveolar walls become v thickened with connective tissue (fibrotic) - fibrosis arises from infection, autoimmune disease, hypersensitivity to inspired substances, exposure to toxic airborne chemicals, etx

Question 36

symptoms of diffusion disease

Answer 36

shortness of breath
poor oxygenation of blood
don’t affect elimination of co2 as it diffuses more rapidly than oxygen