Ch. 9: Cardiovascular Responses To Acute Aerobic Exercise

Front 1

what happens to whole body oxygen consumption (VO2) during aerobic exercise?

Back 1

VO2 increases in proportion to exercise intensity

it is the function of increases in cardiac output (Q) and oxygen extraction (a-v O2 dif)

VO2 = Q x a-v O2 diff

Front 2

what is a-v O2?

Back 2

the difference in oxygen content between arterial and venous blood.

amount of oxygen extracted

Front 3

why does Q increase during aerobic exercise?

Back 3

to accomodate the increased blood and oxygen demand of working tissues

Front 4

how does Q increase?

Back 4

both SV and HR

result from neural and hormonal mechanisms as well as alteration in venous return and ventricular preload

Front 5

how much does Q increase during exercise in moderately trained men?

Back 5

5 L/min to 25 L/min

Front 6

how does Q increase during steady state exercise?

Back 6

cadiac output increases rapidly and may plateau within the first few minutes of exercise

Front 7

what is the level of Q dependent on during exercise?

Back 7

exercise intensity

Front 8

How is steady state Q output maintained?

Back 8

increased SV and HR

both increase rapidly in proportion to exercise intensity and then plateau within first several minutes of exercise

Front 9

what happens to Q during incremental exercise to maximal efforts?

Back 9

Q either experiences an attenuated rise or reaches a plateau

Front 10

components that increase HR

Back 10

Hormones - norepinephrine and epinephrine

Neural Factors

- Autonomic nervous system (sympathetic activity increases; parasympathetic activity decreases)

- Chemoreceptors

- mechanoreceptors (in response toe muscle contraction)

Front 11

components that increase SV

Back 11

1. increase preload

2. decrease afterload

3. increased contractility

Front 12

central command

Back 12

a coordinated autonomic response initiate by the medulla when muscle are stimulated

- immediate withdrawal of parasympathetic outflow to the heart

- increased sympathetic activation

Front 13

what happens to HR during aerobic activity?

Back 13

increases linearly in proportion to exercise intensity.

may plateau as maximal exercise is approached.

Front 14

what is the increase in SV a funtion of?

Back 14

1. increase in preload

2. decrease in afterload

3. increase in intrinsic contractility

Front 15

what increases ventricular preload?

Back 15

greater venous return

-results in more forceful contraction

Front 16

why does afterload decrease?

Back 16

declining total peripheral resistance

Front 17

when is there a greater contribution from the frank-starling mechanism?

Back 17

during low-intensity exercise.

SV increases ~30% at low-intensity exercise and changes very little as exercise intensity increases.

initial increase in SV due to rise in EDV from greater venous return

Front 18

what happens to venous return during moderate-high intensity exercise.

Back 18

venous return becomes limited by a continued dramatic drop in vascular resistance and EDV plateaus and may even begin to decline.

Front 19

ventricular suction

Back 19

the increase in the pressure gradient between the atria and ventricles which enhances ventricular filling.

refers to suction-like movement of blood from the left atrium into the left ventricle.

Front 20

what typically is seen in SV as HR increases (may not be seen in highly trained athletes)

Back 20

as HR increases, the duration of diastole decreases, allow less time for ventricular filling. This causes SV and ultimately cardiac output not to be able to increase at high HR (~50% VO2max)

increases in SV may continue up to maximal exercise in highly trained athletes.

Front 21

Adaptations to endurance training

Back 21

1. plasma volume expansion

- enhance ventricular preload

2. ventricular hypertrophy

- enhances cardiac contractility

Front 22

cardiovascular drift

Back 22

occurs during prolonged exercise at higher intensities and warm/humid weather, where central cardiovascular variable that had been previously been at a steady state, begin to drift.

Front 23

what causes cardiovascular drift?

Back 23

- increased body temps

- increased blood flow to skin

- plasma volume is reduced as a result of increased perspiration and increased respiration

* all cause a down drift in SV and HR must compensated in order to maintain cardiac output

Front 24

how is blood redirected by the vasculature during exercise?

Back 24

greater proportion of blood is directed to the skin and skeletal muscles.

proportion of cardiac output to the heart remains the same (mean more blood during exercise).

Front 25

what happens to MAP during aerobic exercise?

Back 25

increases as a function of a rising systolic blood pressure.

SBP increases through increase in cardiac output.

DBP stays about the same. Rise in SBP and no change in DBP results in modest rise in MAP

Front 26

what happens to SBP as exercise approaches maximum?

Back 26

SBP begins to plateau as a result in limits in cardiac output.

Front 27

what happens to total peripheral resistance (TPR) during aerobic exercise.

Back 27

decreases as a result of vasodilation in active tissues, primarily the exercising muscles.

vasodilation is elicited by chemical substances released from the exercising muscles and surrounding vessels. release of vasodilators dependent on activity of muscles (more activity = greater vasodilator stimulus).

Front 28

what is responsible for the proper distribution of blood flow during exercise?

Back 28

sympathetic vasoconstriction and funtional sympatholysis

Front 29

exercise hyperemia

Back 29

the rise in muscle blood flow observed during exercise

- factors contributing:

1. Vasodilation

2. Mechanical action (flow mediated vasodilation and muscle pump)

Front 30

vasoactive substances

Back 30

1. hydrogen ions

2. oxygen

3. potassium

4. ATP

5. acetylcholine

6. nitric oxide (NO)

Front 31

other factors contributing to vasodialtion

Back 31

decreased pH resulting from increased metabolic activity

low muscle oxygen levels

Front 32

how does acetylcholine affect vasodilation

Back 32

may induce vasodilation through endothelial cell-mediated pathway

Front 33

flow-mediated dilation

Back 33

NO availability and release is initiated by blood flow

Front 34

conducted vasodilation

Back 34

vasodilation in distal vessels spreads proximally through the vasculature

Front 35

what happens to capillary perfusion during aerobic exercise?

Back 35

increases in proportion to the amount of active muscle mass.

Front 36

what happens to skin blood flow with aerobic exercise

Back 36

increased proportion of Q is distributed to the cutaneous circulation to allow heat loss and maintain core temperature.

Front 37

what happens with coronary blood flow during aerobic exercise?

Back 37

increased oxygen demand of cardiac muscle during exercise is met almost exclusively by an increase in coronary blood flow, which is proportional to the rise in HR.

Front 38

how is cadiac oxygen consumption measured?

Back 38

rate-pulse pressure

HR x SBP

Front 39

what happens to arterial compliance with acute aerobic exercise?

Back 39

increases arterial compliance

Front 40

what happens to blood volume during aerobic exercise?

Back 40

plasma volume decreases as a result of fluid shifts between intra and extracellular compartments and fluid loss through evaporation

exercise in extreme heat exacerbates fluid loss.

Front 41

what happens to blood flow as plasma volume is lost

Back 41

it slows and more energy is needed, Q output decreases and HR must increase to maintain the Q necessary for working muscles

Front 42

what does aerobic exercise do to platelets

Back 42

increase platelet activation and aggregation

Front 43

when does the enhancement of fibronolysis greatest?

Back 43

immediately after exercise