Exercise; the CV and Respiratory Responses Flashcards
Explain the relationship between O2 consumption and work.
Linear relationship between o2 consumption and work - once O2 max is reached a small further increase in work can be performed anaerobically.
What is VO2max?
The maximum rate at which a human uses O2 during dynamic exercise.
VO2 max =
Cardiac output x (arterial - mixed venous O2 content)
ie, Litres of O2 containing blood delivered each minute x amount of O2 removed from each litre.
What is max HR dependant on?
Age!
maxHR = 220 - age
What is resting and submax HR dependent on?
Fitness.
Increase fitness, decrease HR.
Heart has more time to fill!
BP=
And explain changes in BP with severe exercise.
BP = CO x TPR
Systolic increase progressively with increaseing exercise intensities.
Diastolic changes less - increase or decreases a small amount in different subjects.
What is the relationship between mitochondrial capacity and VO2 max?
Increase ATP man…increase VO2 max - linearly!
Resting and max exercise HR vaules?
70bpm
192bpm
Resting and max exercise SV?
72ml
90ml
Resting and max exercise CO?
5L
20L
Resting and max exercise (a-v)O2 content?
5ml/dl
16.5ml/dl
Resting and max exercise O2 consumption?
250 ml/min
2800 ml/min
Bed rest vs Sedentary vs Training?
Increase VO2 max due to increased O2 extraction and increase CO.
How is regional blood controlled in active muscle?
Vasodilation due to local metabolites acting on vascular smooth muscle (increased pCO2, decrease pO2, increased H+, increased adenosine and increased NO).
= increase BP = increased BF.
How is regional blood flow controlled in inactive muscle and splanchnic circulation?
Sympathetic vasoconstriction.
How is regional blood flow to the skin controlled?
Initial vasoconstriction followed by vasodilation sue to core temperature rise and then at max exercise it falls again.
What is the net effect of controlling regional blood flow during exercise?
Decrease TPR.
Is redistribution an appropriate term?
There is a massive increase in CO and all in all only about 600ml is actually ‘redistributed’.
What increases to increase CO?
Increase is HR
Modest increase in SV due to…
…enhanced filling of the heart (increased VR)
…enhanced emptying (sympathetically mediated increase in contractility).
How is the increase O2 consumption by muscles achieved?
Increased BF to active muscles (vasodilation/increased BP)
Increase removal of O2 from each ml of blod passing through the tissues.
How is the increased O2 release from Hb aided?
By low tissue pO2.
By decreased affinity of Hb for O2 (shift of the oxyHb dissociation curve to the right, caused by increase in CO2, H+ and temperature.
Endurance training - what adaptations occur because of it?
Increases max CO, increases capiliarity, increases~ of mitochondria, increase # of enzymes of oxidative metabolism, increased reliance on fat and glycogen sparing.
BP and dynamic exercise?
BP = CO x TPR.
Increase CO, decrease TPR….little change in diastolic, increase systolic meaning mean BP increases moderately.
BP and isometric exercise (sustained muscle contractions)?
Increase BP (systolic and diastolic) and increase HR. For any given O2 consumotion - the BP rise is greater than in dynamic exercise and falls to a plateau.
Ventilation =
Tidal volume x respiratory frequency.
Alveolar ventilation =
(Tidal volume - dead space volume) x frequency
Alveolar and arterial PCO2 depend on what?
The balance between CO2 production and alveolar ventilation.
arteriolar PCO2 is proportional to VCO2/VA.
Why does ventilation increase linearly but the rise more steeply?
Extra stimulus to breathing in heavy exercsise is thought to be caused by stimulation of peripheral chemoreceptors by H+ from glycolysis.
McArdles syndrome?
Can’t produce lactate but still have an anaerobic threshold.
Glycogen depletion?
Decouples ventilatory and lactate thresholds - ventilation earlier, lactate later.
How are CO and ventilation matched?
By central command (feedforward), and peripheral mechanisms (metabolic, mechano, chemo and baro receptors).
Is PaO2 well maintained?
Normally - but in athletes - faster blood flow therefore PaO2 decreases as it is not as saturated.
