CV physiology II Flashcards
what is the arteries function
establish bulk flow and driving pressure
(doesn’t care where the blood goes)
what is the arterioles function
regulate blood flow
distribute blood to different regions
what is the function of capillaries
sites for gas exchange with tissues
what is the function of veins / venules
regulate flow return
how does a-VO2 difference change with intensity
widens the a-VO2 difference as intensity increases
how does arterial O2 content change as exercise intensity increases
stays constant
- increased ventilation ensures nearly complete arterial saturation
how does venous O2 content change as exercise intensity increases
declines
- more O2 taken up by muscles
what determines HR
tradeoff between vagal tone and sympathetic activation
vagal tone = high at rest, low during exercise
sympathetic activation = high during exercise
what is SV
difference in ventricular volume at the end of diastole and end of systole
mL/beat
SV = EDV - ESV
what is ejection fraction
fraction (%) of blood pumped out of LV relative to total volume of LV
EF = SV / EDV
what is the difference in SV and EDV in trained individuals
SV and EDV higher in trained
- bigger and stronger heart
ejection fraction is almost the same because it’s measured as a percentage (more blood in = more blood out)
what is cardiac output
total volume of blood pumped by heart in 1 min
CO = HR x SV
- one of the most important determinants of exercise performance
what is the difference in CO at rest between trained and untrained
similar
- trained have higher SV but lower HR
what is the fick equation
oxygen uptake is equal to the product of Q and oxygen extraction
VO2 = Q x a-VO2 difference
how to measure the variables in the fick equation
VO2 = measured on metabolic cart - non invasive
Q = calculate indirectly - non invasive (similar to ECG)
a-VO2 difference = calculate directly
- invasive - not easy to measure
- need to insert catheter in artery and vein and measure the difference between the two
how do HR, SV, and a-VO2 difference change with exercise intensity
HR - increases linearly
SV - increases and plateaus (around 30-50% of VO2 max)
a-VO2 difference - increases linearly
what is intrinsic regulation of HR
heart can maintain it’s own rhythm (~100bpm)
- SA node = pacemaker
what are the factors involved in extrinsic regulation of HR
PNS/SNS
central motor command
endocrine (norepi/epi)
peripheral input
what is the effect of PNS and SNS on HR
PNS decreases HR - predominate at rest
- inputs to SA node, and AV node (concentrated in the atria)
SNS increases HR - predominate during exercise
- inputs to myocardium (whole heart)
what is the effect of central motor command on HR
signals for motor activity
increases HR
what is the effect of norepi/epi on HR
increases HR (part of SNS)
what is the effect of peripheral input on HR (mechanoreceptors)
decrease HR
- baroreceptors keep HR down during rest
- muscle metaboreceptors decrease HR (parasympathetic)
what is the effect of peripheral input on HR (chemoreceptors)
increases HR
- group III/IV afferents more active during exercise
what are the factors determining EDV (not infinite)
venous return
- how much blood from periphery can push back to the heart
ventricular distensibility
- how much the heart can increase in size (elasticity of the heart)
