Lecture 5

Question 1

what are the two key stages that dictate exchange of O2 and CO2 (what are they and what are they driven by)

Answer 1

alveolar ventilation
- mass flow of air
- driven by pressure gradient of air

alveolar blood transfer
- diffusion of each gas
- driven by pressure gradient of each gas

Question 2

what is the equation of tidal volume

Answer 2

tidal volume = alveolar volume + dead space volume

Question 3

does dead space contribute to gas exchange

Answer 3

dead space does not contribute to gas exchange

Question 4

what is anatomic dead space

Answer 4

it is due to structural, non alveolar volume of the respiratory tract

Question 5

what is physiologic dead space

Answer 5

it includes ventilation into alveoli that are used for gas exchange, because ventilation of those alveoli is greater than perfusion

Question 6

alveolar ventilation is controlled by inspiratory ….

Answer 6

• duration
• force (by recruitment and neural frequency)
• frequency
• resistance (of airways)

Question 7

what is cyclic ventilation due to

Answer 7

inherently rhythmic inspiratory neurons

• in the medulla

Question 8

what are the excitatory and inhibitory stimuli that modify the ventilation cycle

Answer 8

• neural stimuli
• hormonal stimuli

they can act directly or indirectly on the respiratory centre in medulla

Question 9

at rest what is the main detector of the chemical state of arterial blood

Answer 9

mainly chemoreceptors

Question 10

what are central chemoreceptors and what are they sensitive to

Answer 10

Localised chemosensitive medullary neurons

• show strong CO2 sensitivity (via pH of CSF)

Question 11

what are peripheral chemoreceptors

Answer 11

carotid and aortic bodies

Question 12

is ventilation more sensitive to CO2 or O2

Answer 12

CO2

Question 13

what is phase 1 of the ventilatory response

Answer 13

rapid increase at onset of exercise

Question 14

what is phase 2 of the ventilatory response

Answer 14

exponential increase

Question 15

what is phase 3 of the ventilatory response

Answer 15

plateau = (light to moderate exercise only)

Question 16

what is the last phase of the ventilatory response

Answer 16

immediate drop as you stop and then slower exponential decrease in recovery

Question 17

during exercise PACO2 and PaO2 are somewhat stable, are they still the main factor controlling ventilation like at rest

Answer 17

no, neurogenic factors dominate during exercise

Question 18

what type of control does the central command do during exercise to ventilatory control (neurogenic factor)

Answer 18

feedforward control
- Motor cortex output “spill-over” irradiates medulla

Question 19

what type of control does the Muscle ‘Ergoreceptors do during exercise to ventilatory control (neurogenic factor)

Answer 19

feedback control

Question 20

what are the two types of Muscle Ergoreceptors and when do they come into play of the ventilatory response

Answer 20

• Mechanoreceptors. Esp. early (phase 1 & 2)
• Metaboreceptors (chemoreceptors) Esp. to phase 3

Question 21

what are other ergoreceptors in the ventilatory response

Answer 21

• Intercostal and diaphragm spindles
• Heart mechanoreceptors (pressure)
• Lung CO2 (CO2 Flow)
• Lung & Airways (flow, pressure, volume, tension)
• Temperature

Question 22

what happens to ventilation response during non sustainable exercise

Answer 22

• will rise rapidly
• disproportional to oxygen use
• fails to stabilise
• stays elevated during recovery

Question 23

what form is CO2 mostly carried in the blood

Answer 23

bicarbonate

Question 24

why does the blood become more acidic during exercise

Answer 24

body produces more H+ due to metabolism which makes the blood more acidic

Question 25

what happens to some of the H+ that is produced by working muscle

Answer 25

combines with bicarbonate to form CO2

Question 26

as ventilation increases, which breathing mechanism will increase first and why

Answer 26

tidal volume will increase first becuase it is more economical to do this then to breathe more frequently first

tidal volume = the amount of air moving in and out of the lungs

Question 27

as ventilation increases, which breathing mechanism will increase second

Answer 27

breathing frequency will increase when tidal volume can no longer increase any further, the body is forced to breathe more frequently

Question 28

in terms of ventilation at a given relative exercise load athletes have ….

Answer 28

• less increased ventilation
• less acidity

Question 29

what are the reasons that athletes have different respiratory responses to exercise

Answer 29

• decreased Type II fibres (IIx)
• increased recruit Type I fibres
• increased H+ buffering