Lecture 5 Flashcards
Cardiorespiratory : Breathing in Exercise
what are the two key stages that dictate exchange of O2 and CO2 (what are they and what are they driven by)
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
what is the equation of tidal volume
tidal volume = alveolar volume + dead space volume
does dead space contribute to gas exchange
dead space does not contribute to gas exchange
what is anatomic dead space
it is due to structural, non alveolar volume of the respiratory tract
what is physiologic dead space
it includes ventilation into alveoli that are used for gas exchange, because ventilation of those alveoli is greater than perfusion
alveolar ventilation is controlled by inspiratory ….
- duration
- force (by recruitment and neural frequency)
- frequency
- resistance (of airways)
what is cyclic ventilation due to
inherently rhythmic inspiratory neurons
- in the medulla
what are the excitatory and inhibitory stimuli that modify the ventilation cycle
- neural stimuli
- hormonal stimuli
they can act directly or indirectly on the respiratory centre in medulla
at rest what is the main detector of the chemical state of arterial blood
mainly chemoreceptors
what are central chemoreceptors and what are they sensitive to
Localised chemosensitive medullary neurons
- show strong CO2 sensitivity (via pH of CSF)
what are peripheral chemoreceptors
carotid and aortic bodies
is ventilation more sensitive to CO2 or O2
CO2
what is phase 1 of the ventilatory response
rapid increase at onset of exercise
what is phase 2 of the ventilatory response
exponential increase
what is phase 3 of the ventilatory response
plateau = (light to moderate exercise only)
what is the last phase of the ventilatory response
immediate drop as you stop and then slower exponential decrease in recovery
during exercise PACO2 and PaO2 are somewhat stable, are they still the main factor controlling ventilation like at rest
no, neurogenic factors dominate during exercise
what type of control does the central command do during exercise to ventilatory control (neurogenic factor)
feedforward control
- Motor cortex output “spill-over” irradiates medulla
what type of control does the Muscle ‘Ergoreceptors do during exercise to ventilatory control (neurogenic factor)
feedback control
what are the two types of Muscle Ergoreceptors and when do they come into play of the ventilatory response
- Mechanoreceptors. Esp. early (phase 1 & 2)
- Metaboreceptors (chemoreceptors) Esp. to phase 3
what are other ergoreceptors in the ventilatory response
- Intercostal and diaphragm spindles
- Heart mechanoreceptors (pressure)
- Lung CO2 (CO2 Flow)
- Lung & Airways (flow, pressure, volume, tension)
- Temperature
what happens to ventilation response during non sustainable exercise
- will rise rapidly
- disproportional to oxygen use
- fails to stabilise
- stays elevated during recovery
what form is CO2 mostly carried in the blood
bicarbonate
why does the blood become more acidic during exercise
body produces more H+ due to metabolism which makes the blood more acidic
what happens to some of the H+ that is produced by working muscle
combines with bicarbonate to form CO2
as ventilation increases, which breathing mechanism will increase first and why
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
as ventilation increases, which breathing mechanism will increase second
breathing frequency will increase when tidal volume can no longer increase any further, the body is forced to breathe more frequently
in terms of ventilation at a given relative exercise load athletes have ….
- less increased ventilation
- less acidity
what are the reasons that athletes have different respiratory responses to exercise
- decreased Type II fibres (IIx)
- increased recruit Type I fibres
- increased H+ buffering
