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Exercise Physiology > Chapter 9: Circulatory Responses to Exercise > Flashcards

Chapter 9: Circulatory Responses to Exercise Flashcards

1
Q

purposes of the cardiorespiratory system

A

1) transport O2 and nutrients to tissues
2) removal of CO2 and wastes from tissues
3) regulation of body temperature

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2
Q

two major changes to blood flow during exercise

A

1) increased cardiac output
2) redistribution of blood flow from inactive organs to active muscle

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3
Q

describe the pulmonary circuit, which side of the heart is it?

A

right side of the heart, pumps deoxygenated blood to the lungs via pulmonary arteries and returns oxygenated blood to the left side of the heart via pulmonary veins

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4
Q

describe the systemic circuit, which side of the heart is it?

A

left side of the heart, pumps oxygenated blood to the whole body via arteries and returns deoxygenated blood to the right side of the heart via veins

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5
Q

what is the liquid portion of blood? what does it contain?

A

plasma; contains ions, proteins, hormones

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6
Q

3 cells found in blood and their functions

A

1) red blood cells- contain hemoglobin to carry O2
2) white blood cells- prevent infection
3) platelets- important in blood clotting

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7
Q

define hematocrit

A

percentage of blood composed of packed RBCs

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8
Q

how do we define blood flow? what is it directly and inversely proportional to?

A

directly proportional to the pressure difference between the two ends of the system and inversely proportional to resistance (blood flow = change in pressure/ resistance)

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9
Q

what is pressure proportional to?

A

the difference between MAP and right atrial pressure (change in pressure)

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10
Q

describe diastole, when are atrioventricular valves open?

A

pressure in ventricles is low, filling with blood from atria, AV valves open when ventricular P < atrial P

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11
Q

describe systole, when are semilunar valves open?

A

pressure in ventricles rises, blood ejected in pulmonary and systemic circulation, semilunar valves open when ventricular P > aortic P

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12
Q

at rest, how do diastole and systole compare?

A

diastole is longer than systole

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13
Q

during exercise, how do diastole and systole compare?

A

systole is longer than diastole, but both are shorter

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14
Q

define cardiac output

A

amount of blood pumped by the heart each minute (Q = HR x SV)

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15
Q

what does cardiac output depend on?

A

training state and sex

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16
Q

what inputs regulate heart rate?

A

sympathetic and parasympathetic input

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17
Q

what inputs regulate stroke volume?

A

sympathetic nervous system

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18
Q

how does the parasympathetic nervous system regulate HR?

A

postganglionic nerve (vagus nerve) releases acetylcholine onto mAch (muscarinic cholinergic) receptors on autorhythmic cells of the SA and AV node —> hyperpolarization of the cell —> inhibits SA and AV node —> slows HR

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19
Q

how does the sympathetic nervous system regulate heart rate?

A

postganglionic nerves (cardiac accelerator nerves) release norepinephrine (catecholamines) onto B1-ADR receptors of autorhythmic cells on the SA and AV node —> depolarizes cell —> stimulate AV and SA node —> increases HR

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20
Q

what is the increase in heart rate at the onset of exercise due to? up to what HR?

A

parasympathetic withdrawal, up to 100 bpm

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21
Q

what is the increase in HR due to later on (after onset)?

A

sympathetic input

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22
Q

what does a wide variation in resting HRV indicate?

A

good index of “healthy” balance between SNS and PNS

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23
Q

what does a low variation in resting HRV indicate?

A

imbalance in autonomic regulation —> excellent predictor of cardiovascular dysfunction

24
Q

why is high heart variability good?

A

indicates both sympathetic and parasympathetic are active; low variability shows a take over of sympathetic

25
Q

3 factors influencing stroke volume

A

1) end diastolic volume
2) average aortic blood pressure
3) strength of ventricular contractility

26
Q

what is EDV? how does it affect SV?

A

EDV is the volume of blood in the ventricles at the end of diastole, increased EDV increases SV

27
Q

describe the Frank-Starling mechanism , what is it dependent on?

A

greater EDV results in a more forceful contraction due to stretch of ventricles and it is dependent on venous return

28
Q

3 factors increasing venous return

A

1) venoconstriction
2) skeletal muscle pump
3) respiratory pump

29
Q

how is venoconstriction accomplished?

A

via SNS input

30
Q

how does the skeletal muscle pump increase venous return?

A

rhythmic skeletal muscle contractions force blood in the extremities toward the heart (one way valves in veins prevent back flow)

31
Q

how does the respiratory pump increase venous return?

A

changes in thoracic pressure (in the diaphragm) pull blood toward the heart

32
Q

besides venous return, what else might affect EDV?

A

filling time

33
Q

what is filling time affected by? how does lying supine affect filling time?

A

increased heart rate decreases filling time therefore decreasing EDV; lying supine rather than standing allows for more filling which increases EDV

34
Q

what is afterload? how does it affect SV?

A

pressure the ventricles must pump against to eject blood during contraction; increased afterload decreases SV

35
Q

how does ventricular contractility (ionotropy) increase SV?

A

catecholamines bind B1-ADR on contractile cells of the heart —> depolarizes cell —> more forceful contraction —> decreased ESV —> increased SV

36
Q

what is increased SV during exercise due to?

A

increased EDV (preload) and increased ventricular contractility

37
Q

how does oxygen command during exercise compare to at rest?

A

15-25x greater

38
Q

what two factors increase oxygen delivery during exercise

A

1) increased cardiac output
2) redistribution of blood flow

39
Q

what is increased cardiac output due to at intensities up to 40-60% VO2 max?

A

increased heart rate and increased stroke volume

40
Q

what is increased cardiac output due to at intensities greater than 40-60% of VO2 max?

A

increased heart rate

41
Q

how does stroke volume change during exercise in untrained subjects?

A

increases linearly until high heart rates cause decreased filling time (decreased EDV and SV) and stroke volume plateaus

42
Q

how do changes in stroke volume during upright and supine exercises differ?

A

during supine exercise, peak stroke volume is higher and still plateaus with higher intensities because of higher heart rates

43
Q

how does % cardiac output to working skeletal muscles change from rest to exercise?

A

15-20% of cardiac output to skeletal muscle at rest, and 80-85% of cardiac output to skeletal muscle during maximal exercise

44
Q

which organs get decreased blood flow during exercise?

A

liver, kidneys, GI tract

45
Q

what does redistribution of blood flow depend on? what kind of factors mediate blood flow?

A

metabolic rate; local factors mediate blood flow (autoregulation)

46
Q

what local factors increase blood flow? via what mechanism?

A

local metabolites (e.g. nitric oxide, prostaglandins, ATP, adenosine, and endothelium-derived hyperpolarization) promotes vasodilation to increase blood flow to the working muscles

47
Q

how does arteriovenous oxygen difference increase during exercise?

A

increases due to higher O2 uptake in tissues for oxidative ATP production, not higher O2 content in arteries

48
Q

how do emotionally charged environments affect HR and BP? via what mechanism?

A

elevate HR and BP due to increases in SNS activity

49
Q

can emotional influence increase peak HR or BP during exercise?

A

no, just increases pre-exercise HR and BP

50
Q

what does the rest to exercise transition look like for HR, SV, and CO?

A

rapidly increase until there is a plateau (during submaximal exercise that is below lactate threshold)

51
Q

during graded exercise, how do heart rate and cardiac output change?

A

increases linearly with increasing work rate and reaches a plateau at 100% VO2 max

52
Q

how does blood pressure change during graded exercise?

A

mean arterial pressure increases linearly (systolic increases and diastolic remains fairly constant)

53
Q

at the same oxygen uptake, what does arm work result in compared to leg work?

A

higher blood pressure due to vasoconstriction of large inactive muscle mass and higher heart rate due to sympathetic stimulation

54
Q

3 factors that recovery of heart rate and blood pressure depend on

A

1) fitness level
2) temperature and humidity
3) duration and intensity of exercise

55
Q

during prolonged exercise, how does cardiac output, heart rate and stroke volume change?

A

cardiac output is maintained:
1) gradual decrease in stroke volume due to dehydration and reduced plasma volume
2) gradual increase in heart rate (cardiovascular drift- particularly in heat)

56
Q

how can you prevent cardiovascular drift during prolonged exercise?

A

lower intensity, drink water, cooler environments

57
Q

what does the decrease in HR, SV, and CO toward resting depend on?

A

1) duration and intensity of exercise
2) training state of subject

Exercise Physiology (25 decks)

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