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A Human Physiology > Cardiac output and blood pressure > Flashcards

Cardiac output and blood pressure Flashcards

1
Q

What is the CO?

A

Volume of blood pumped out by heart per unit of time; l/min; SV*HR

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2
Q

What is the typical values for SV, HR and thus CO at rest?

A 
SV = 80ml
HR = 70bpm
CO = 5.6 l/min
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3
Q

What is the relationship between workload and HR?

A

HR has linear relationship

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4
Q

What is the relationship between workload and SV?

A

Increases, plateaus, then decreases; as HR increases above peak SV, there’s less time for ventricles to fill, decreasing SV

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5
Q

What is predominant way that elite athletes alter their CO being max effort exercise?

A

By increasing SV

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6
Q

What are three ways that HR is controlled?

A

ANS, hormones, and body temperature

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7
Q

What is the effect of parasympathetic stimulation on the HR?

A

Nerve endings secrete ACh @ SAN and AVN; ACh is inhibitory on cardiac muscle, hyperpolarising membranes and causing depolarising drift to become slower = slower SAN rhythm

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8
Q

What is the effect of sympathetic stimulation on the HR?

A

Nerve endings secrete NE @ SAN, AVN, and cardiac muscle; NE is excitatory on cardiac muscle, depolarising membranes further, causing depolarising drift to become faster = faster SAN rhythm. NE also shortens AVN delay, myocyte action potential, and increases speed of relaxation

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9
Q

What hormones increase HR?

A

NE and Epi in bloodstream act on beta receptors, increasing HR

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10
Q

How does temperature affect pacemaker rate?

A

Cold temperatures cause decrease, whilst warmer temperatures cause increase

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11
Q

What are the two ways that SV are controlled?

A

Force by which muscle cells contract; arterial pressure against which they have to eject blood

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12
Q

What are the two processes that regulate the force of contraction of the heart?

A

Length-tension properties of cardiac muscle cells; effects of hormonal influence on the contractility of cardiac muscle

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13
Q

How does hormonal activity affect the contractility of the cardiac muscle?

A

Sympathetic nerve activity and circulating catecholamines increase contractility = greater SV

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14
Q

How does venous return influence SV?

A

Increased venous return increases end-diastolic volume = increased SV

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15
Q

What law describes the relationship between end-diastolic volume and SV?

A

Starling’s law of the heart

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16
Q

What is the driving force for flow within the CV system?

A

Pressure; gradient is present between arteries and veins; pressure must be high enough to create flow but not too high to put excessive stress on CV system

17
Q

What is the difference in the blood pressure maintenance in the veins and arteries?

A

Arteries have a pulsalite blood pressure due to the pressure oscillations of the heat; veins have a continuous blood pressure due to the loss of forward energy (mainly due to friction)

18
Q

How is blood pressure measured clinically?

A

Cuff pressure; sound of artery opening and closing continuously

19
Q

What would happen if the cuff pressure was below diastolic pressure?

A

Blood would flow freely and no sound would be heard

20
Q

What would happen in the cuff pressure was above systolic pressure?

A

Blood would not flow, and no sound would be heard

21
Q

What must the cuff pressure be in order or blood pressure to be heard?

A

Must be between diastolic ans systolic pressures (diastolic < cuff < systolic)

22
Q

What is mean arterial pressure?

A

Diastolic pressure + (systolic-diastolic)/3

23
Q

What value is MAP closer to?

A

Diastolic, as lasts almost twice the duration of systole

24
Q

What is the normal value for blood pressure?

A

120/80; ~95mmHg MAP

25
Q

Why does blood pressure vary?

A

MAP increases with age as arteries become stiffer due to loss of elasticity; women typically have lower blood pressure than men; pressure in foot is higher than in head due to hydrostatic pressure; painful stimulus, sex, and being awake and mobile more likely to cause increased blood pressure than rest/sleep

26
Q

What is the effect of dynamic exercise on MAP?

A

Remains relatively steady; increase in systolic pressure, decrease in diastolic pressure; sympathetic activity constricts vessels not related to exercise and dilates vessels to skeletal muscles, so total peripheral resistance is almost constant

27
Q

What is the effect of static exercise on MAP?

A

MAP dramatically rises; both systolic and diastolic increased; sympathetic activity constricts vessels and increases total peripheral resistance

28
Q

What physiological factors determine MAP?

A

MAP = CO*TPR

29
Q

What is TPR?

A

Sum of resistance in organs of the body

A Human Physiology (24 decks)

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