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Question 1

main cardiovascular responses to acute exercise

Answer 1

• > blood flow redistribution
• > cardiovascular drift
• > competition for blood supply
• > blood oxygen content

Question 2

what happens when blood flow is redistributed during exercise

Answer 2

- > increased cardiac output which leads to increased available blood flow

*must redirect BF to areas w/greatest metabolic needs

- > sympathetic vasoconstriction shunts blood away from less active regions (via splanchnic circulation and kidneys)

- > local vasodilation permits additional BF in exercising muscles

*local VD triggered by metabolic and endothelial product

- > as temp increases, skin VD also increases

*decreased symp VC, inc symp VD permits heat loss through the skin

Question 3

cardiovascular drift

Answer 3

upward drift of HR over time

• > associated with increased core temp and dehydration

as SV drifts down

• > skin BF increases
• > plasma vol decreases (sweating)
• > venous return/preload decreases

HR drifts increase to compensate (Q in maintained)

Question 4

describe/explain the competition for blood supply

Answer 4

exercise and others demand blood flow as such they must compete for a set Q

• > multiple demands may decrease muscle blood flow

exercising (muscle) + eating

exercising (muscle) + nothing

Question 5

how does blood content change during exercise

Answer 5

(a-v) O2 difference

- > 1ml O2 / 100mL of blood

resting: ~6mL O2/ 100ml blood
active: ~16-17mL O2/ 100mL of blood

Mixed venous O2 >or equal 4mL O2 /100mL blood

• > venous O2 from active muscle ~0ml
• > venous O2 from inactive muscles > active muscles
• > increases mixed venous O2 content

Question 6

central regulation of cardiovascular responses

Answer 6

What stimulates rapid change in HR, Q, and BP during exercise

• > precede metabolite buildup in muscle
• > HR increases within 1s of the onset of exercise

Central Command

• > higher brain centres
• > co-activates motor and cardiovascular centres

Question 7

what is the body’s first priority during the onset of exercise

Answer 7

• > maintenance of BP

cardiovascular responses to exercise are complex, fast, and finely tuned

Question 8

ventilation during exercise

Answer 8

immediate increase in ventilation during exercise

• > begins before muscle contractions
• > anticipatory response from central command

gradual second phase of increase in vent.

• > driven by chem changes in arterial blood; inc CO2, H+ sensed by chemoreceptors; right arterial stretch receptors

ventilation increase in proportional to metabolic needs of muscle

• > at low exercise intensity: only tidal volume increases
• > at high exercise intensity: rate also increases

ventilation recovery after exercise delayed

• > recovery takes several minutes
• > may be regulated by blood pH, PCO2 and tempp

Question 9

why can the valsalva maneuver be potentially dangerous

Answer 9

if you have high blood pressure/ are exercising hard, it will increase intra-abdominal and intra-thorasic pressure

these high pressures can colapse the great veins - > decreased venous return - > decreased Q - > decreased arterial BP

Question 10

how is ventilation and energy metabolism related

Answer 10

ventilation matches metabolic rate

• ventilatory equivalent for O2*
• > Ve/VO2 (L air breathed / L O2 consumed/min)
• > index of how well control of breathing matched to body’s demand for oxygen
• Ventilatory threshold*
• > point where L air breathed > L O2 consumed
• > associated with lactate threshold and increased PCO2

Question 11

estimating lactate threshold

Answer 11

• ventilatory threshold as a surrogate measure?*
• > excess lactic acid+ sodium bicarbonate
• > result: excess Na lactate, H2O and Co2
• > lactic acid, CO2 accumulate simultaneously

refined to better estimate lactate threshold

• > anaerobic threshold
• > monito both VE/VO2 and VE/VCO2

Question 12

how can ventilation create limitations to performance

Answer 12

ventilation normally does not limit performance

• > respiratory muscles account for 10% of VO2, 15% of Q during heavy exercise
• > respiratory muscles are very fatigue resistant
• > airway resistance and gas diffusion normally not limiting factors at sea level
• > restrictive or obstructive respiratory disorders can be limitint

exception: elite endurance-trained athletes exercising at high intensity

• > ventilation may be limiting
• > ventialtion-perfusion mismatch
• > exercise induced arterial hypoxia (EIAH)