Cardio response to exercise 1 and 2 Flashcards
How can we increase O2 delivery to muscle?
increasing flood flow
increasing O2 extractino from the blood
increasing the amount of O2 in the blood
how is the sympathetic nervous system activated during exercise?
activated by psychic stimuli (hypothalamus, frontal lobe etc )
irradiation from corticospinal tracts to medullary cardiovascular regulating centers
muscle ergoreceptors, joint receptors etc
how is venous return increased during exercise?
by increased muscle blood flow
increased venoconstriction
increased muscle pump
increased respiatory pump
does increased venous return increase or decrease cardiac output?
increase
an activated SNS has what effect on the cardiac output?
leads to increased cardiac output due to increased venous return, sympathetic nerve activity anc circulating catecholamines - leads to increased heart rate, stroke volume and ejection fraction
what is the maximum heart rate?
200 beats/min
why does the extraction of O2 increase during exercise?
- the diffusion distance between the blood and cells decreases
- increased diffusion gradient
- increased exhange area of the capillary bed
- increased bohr effect
- increased 2,3 DPG
how does the arteriovenous difference of O2 change during exercise?
it goes from
20% arterial O2 - 15% venous O2
to
20% arterial O2 - 5% venous O2
with moderate exercise is there change in arterial blood gases?
no - in moderate exercise there is no change in arterial blood gases
- that means that ventilation exactly keeps pace with the increased pulmonary blood flow and with the decreased mix of venous blood PO2 and increased PCO2
how much is diffusing capacity increased during exercise?
increased X3 b/c of increased CO and pulmonary arterial pressure which opens capillaries and improves the V/Q ratio
What is VO2 max?
the maximum volume of Oxygen that a person can inspire
test VO2 max by increasing exercise intensity and watching levels of O2 rise til it plateaus
how do we express VO2 max?
ml/min/kg
note a sedentary person will have 40ml/min/kg VO2 max
what is oxygen debt?
it refers to the O2 used while the VO2 ramps up with your exercise - you acquire a small amount of O2 debt that is paid off once exercise is finished
actual definition = the VO2 in excess of resting VO2 after the end of exercise - note the O2 debt will be very large if the O2 requirement is greater than the VO2 max
What is this graph showing us?
Two runners with the same VO2 max, but different lactate thresholds
the person in blue has a 60% lactate threshold and the red runner has 70% lactate threshold - this means that the blue runner can run forever theoretically at 60% of their VO2 max… but the red runner can run at 70% of their VO2 max before they build up lactate - so the red runner will be faster!
during exercise when is the anaerobic threshold reached?
when the metabolic demand for O2 exceeds the O2 delivery so that msucles begin to use glycolysis in addition to aerobic metabolism - as a result there is lactic acidosis, arterial blood pH is decreased and breathing is further stimulated through peripheral chemoreceptors causing hyperventilation and a decrease in PCO2
