# Systemic Circulation and Hemodynamics Flashcards

1
Q

the volume of blood contained in the arteries is called what?

A

stressed volume-meaning the blood volume under high pressure

2
Q

which blood vessel type has the highest resistance to blood flow?

A

arterioles

3
Q

what is a special feature of the arterioles besides them having the highest resistance to blood flow?

A

they are also the site where resistance can be changed by alterations in sympathetic nerve activity

4
Q

what is the pressure/ volume like of veins?

A

low pressure; high volume

5
Q

the volume of the blood contained in the veins is called what?

A

unstressed volume- meaning the blood volume under low pressure

6
Q

where is the cross-sectional area the greatest?

A

in the capillaries

7
Q

where is the volume of blood the greatest?

A

in the veins

8
Q

what happens to the resistance and the flow as the diameter of the blood vessel changes?

A

as the diameter increases, the resistance is going to decrease and flow is going to increase; as the diameter decreases, the resistance is going to increase and flow is going to decrease

9
Q

what does Poiseuille’s law calculate?

A

resistance through a tube

10
Q

what happens to the resistance has viscosity goes down?

A

resistance decreases as viscosity decreases

11
Q

when would viscosity decrease?

A

in an anemic state

12
Q

what happens if there is increased hematocrit?

A

it will decrease the flow (because resistance is increased)

13
Q

how would you find the total resistance for vascular resistances that are in a series?

A

you simply add the individual resistances for the total

14
Q

how would you find total resistance for vascular resistance beds that are in parallel?

A

1/ Rtotal= the sum of the 1/R1…1/R2 etc.

15
Q

what does adding resistance beds in series do to the total resistance?

A

it increases the total resistance

16
Q

what does adding resistance beds in parallel do to the total resistance?

A

it decreases the total resistance

17
Q

how are capillaries arrange: series or parallel?

A

capillaries are arranged in parallel–> low resistance

18
Q

where is the site of the greatest control of blood flow and TPR?

A

the arterioles

19
Q

what does increased sympathetic stimulation cause in the blood vessels?

A

vasoconstriction

20
Q

what does vasoconstriction cause?

A

reduced flow, increased TPR or increased pressure

21
Q

what does decreased sympathetic stimulation cause?

A

vasodilation

22
Q

what does vasodilation cause?

A

increased flow, decreased TPR or decreased pressure

23
Q

what is velocity like in arteries? In capillaries?

A

high in arteries and low in capillaries

24
Q

what contributes to blood flow becoming turbulent?

A

when velocity is high, cross sectional area is large, or viscosity is low

25
Q

what is reynold’s number?

A

an equation which takes into account the velocity, cross sectional area, and viscosity to predict when turbulence will occur

26
Q

when is it considered that there is a transition from laminar to turbulent flow?

A

when reynold’s number is greater than 2000

27
Q

what does turbulent blood flow lead to?

A

sound (bruits) and lesions (arteriosclerosis)

28
Q

what is compliance (aka capacitance)?

A

the change in volume/ the change in pressure

29
Q

what is compliance (aka capacitance) the reciprocal of?

A

elastance

30
Q

where is the highest compliance?

A

in the veins

31
Q

where is the lowest compliance found?

A

in the arteries

32
Q

which is more elastic, arteries or veins?

A

arteries

33
Q

blood is being pushed forward not only through the pressure gradient but also through what?

A

the elastic recoil of the arteries

34
Q

when is the elastic recoil of the arteries prominent?

A

during diastole

35
Q

what affect does aging and atherosclerosis have on compliance and how?

A

they decrease compliance by reducing the amount an artery can distend during systole and by reducing the recoil during diastole

36
Q

what is the effect of smooth muscle contraction in veins?

A

you are contracting the blood forward; redistributing blood to the arteries

37
Q

what is the pulsatile nature of the aortic end of the pressure due to?

A

compliance and distention of the walls during ejection and recoil during relaxation

38
Q

which blood vessel sees the largest pressure drop?

A

arterioles

39
Q

what is the driving force for blood flow?

A

the pressure differences that exist between the heart and the blood vessels

40
Q

what is pulse pressure?

A

the difference between systolic and diastolic pressure

41
Q

if all other factors are equal, what does the magnitude of the pulse pressure reflect?

A

the blood ejected from the left ventricle in a single beat AKA STROKE VOLUME

42
Q

how do you calculate the mean arterial pressure?

A

1/3( SBP) + 2/3 (DBP) (bc you spend a lot more time in diastole than you do in systole)

43
Q

what is the normal mean arterial pressure?

A

93.3 mm Hg

44
Q

a decrease in compliance would have what effect on the pulse pressure?

A

a decrease in compliance would cause pulse pressure to increase

45
Q

what effect does arteriosclerosis have on pressure?

A

it increases SBP, MAP, and pulse pressure; DBP does not generally change

46
Q

what effect does aortic stenosis have on pressure?

A

it decreases SBP, MAP, and pulse pressure; DBP does not generally change

47
Q

what is the general rule of thumb for the venous system?

A

low pressure, high compliance, and large volume

48
Q

what effect does venoconstriction have on the venous system?

A

it decreases venous “compliance” with minor changes to the radius of the veins (so there is little resistance change)

49
Q

what is the backflow of blood in veins prevented by?

A

valves

50
Q

what does venous pressure in the cardiac cycle look like?

A

there is an A wave, a C wave, and a V wave

51
Q

when does the A wave occur?

A

during atrial contraction (so between the mid p-wave on the ECG and R wave of the QRS complex)

52
Q

when does the C wave occur?

A

during ventricular contraction

53
Q

what is the C wave caused by?

A

partially by slight backflow of blood into the atria at the onset of ventricular contraction but mainly by the bulging of the AV valves backwards into the atria due to increases in pressure in the ventricles

54
Q

when does the V wave occur?

A

at the end of the ventricular contraction

55
Q

what causes the V wave?

A

slow flow of blood into the atria from veins while the AV valves are closed

56
Q

What are the walls of the arterioles rich with?

A

extensive smooth muscle

57
Q

what is the composition of metarterioles?

A

they have more limited smooth muscle along the walls

58
Q

what do the capillaries have that further control flow?

A

precapillary sphincters

59
Q

in the capillary walls, what allow for the passage of water soluble substances such as glucose or electrolytes?

A

clefts

60
Q

where are clefts found to be very small? Where are clefts found to be very large?

A

Very small in the brain (tight junctions) and very large in the liver and the gut

61
Q

how do lipid soluble substances such as O2 and CO2 pass across the capillary walls?

A

through plasma membranes

62
Q

how do larger molecules pass through the capillary walls?

A

through vesicles

63
Q

Not all capillaries are open all the time; what is vasomotion?

A

it is the term used for the oscillating flow of blood through capillaries, which flows intermittently on and off every few seconds or minutes

64
Q

how does vasomotion occur?

A

from the oscillating contraction of metarterioles and precapillary sphincters

65
Q

what is vasomotion largely regulated by?

A

oxygen levels in the tissues; as oxygen consumption increases in the tissue, the frequency of vasomotion and duration the sphincters remain open increases to increase blood flow

66
Q

what does the starling equation calculate?

A

the flow of water either out of a capillary or drawing into the capillary

67
Q

what does a positive starling number indiccate?

A

that the flow of water is out of the capillary

68
Q

what does a negative starling number indicate?

A

there is a drawing of water into the capillary

69
Q

what represents fluid moving out of the capillary (+)?

A

filtration

70
Q

what represents fluid moving into the capillary (-)?

A

absorption

71
Q

what 2 forces act on the fluid exchange that is occurring in capillaries?

A

hydrostatic pressure and osmotic/oncotic pressure

72
Q

what type of forces are the hydrostatic pressures?

A

pushing forces

73
Q

what type of forces are the osmotic/oncotic forces?

A

pulling forces

74
Q

what is the equation used for fluid exchange across the capillary walls?

A
```J= [(Pcap-Pinterstial)- (Osmotic pressure cap.-osmotic pressure interstitial)}
J= flow```
75
Q

what is the general rule about the hydrostatic pressure at the arteriole side and what effect does this have?

A

it is usually higher on the capillary side; so therefore, you are more likely to see filtration (+)

76
Q

what is the general rule about the hydrostatic pressure at the venous side?

A

it is lower, so you are more likely to see absorption (-)

77
Q

what is the capillary osmotic pressure caused by?

A

plasma proteins that tend to draw fluid from the interstitial fluid into the blood

78
Q

what is the interstitial fluid pressure?

A

the pressure to force fluid into the capillary from the interstitial fluid

79
Q

what is the interstitial osmotic pressure?

A

tends to pull fluid from the capillary into the interstitial fluid

80
Q

how do the lymphatics re-enter venous circulation?

A

at the subclavian vein

81
Q

what effect does elevated venous pressure have on Pc? and when might you have this?

A

Pc can be increased by elevated venous pressure; this can occur during right-sided heart failure

82
Q

when can Pi be altered?

A

by restricted lymphatic flow or increased driving force out of a capillary

83
Q

when can osmotic pressure of the capillary be decreased?

A

by reduced levels of albumin (such as in starvation or liver failure)- causes fluid to stay in the interstitial space

84
Q

when might interstitial osmotic pressure be altered?

A

by restricted lymph flow or inflammation

85
Q

what is acute control of blood flow achieved by?

A

rapid changes in local vasodilation or vasoconstriction of arterioles, metarterioles, and precapillary sphincters

86
Q

what is autoregulation?

A

the maintenance of a constant blood flow to an organ in the face of changing arterial pressure

87
Q

what does the vasodilator theory state?

A

decreased oxygen availability increases the formation of vasodilator substances

88
Q

what are the vasodilator substances?

A

89
Q

what does the oxygen demand theory state?

A

as oxygen levels rise or decrease the contraction of precapillary sphincter smooth muscle constricts or relaxes

90
Q

what is active hyperemia?

A

the concept that blood flow to an organ is proportional to its metabolic activity

91
Q

what is reactive hyperemia?

A

an increase in blood flow in response to or reacting to a prior period of decreased blood flow

92
Q

what is the most important mechanism for coronary circulation?

A

local metabolic control

93
Q

what is the most important mechanism for cerebral circulation?

A

local metabolic control

94
Q

what is the most important mechanism during exercise for skeletal muscle?

A

local metabolic control

95
Q

what is the most important mechanism during rest for skeletal muscle?

A

sympathetic control

96
Q

what is the most important mechanism for temperature regulation of the skin?

A

sympathetic control

97
Q

what is the most important mechanism for pulmonary circulation?

A

local metabolic control

98
Q

what is the most important mechanism for renal circulation?

A

local metabolic control

99
Q

what NT causes vasocontriction?

A

norepinephrine and epinephrine (norepinephrine greater than epinephrine)

100
Q

what effect does Angiotensin II have on blood vessels?

A

it acts as a vasoconstrictor

101
Q

what effect does vasopressin have on the blood vessels?

A

vasoconstrictor

102
Q

what effect does serotonin have on the blood vessels?

A

it acts as a vasoconstrictor

103
Q

what are the two main vasodilators we discussed?

A

104
Q

what ions are considered vasodilators?

A

K+, Mg2+, H+, acetate, and citrate, and CO2

105
Q

what is coronary blood flow mostly regulated by?

A

local control mechanisms- largely under metabolic control

106
Q

what is the rate and contractility of the heart controlled by?

A

the sympathetic nervous system

107
Q

when does coronary blood flow begin and when does it end?

A

begins during ventricular repolarization and lasts into diastole

108
Q

when is coronary blood flow partially occluded?

A

during systole

109
Q

what is almost entirely controlling the cerebral blood flow?

A

metabolic control, Pco2, and H+

110
Q

injury to the head can result in what?

A

vasodilation and edema

111
Q

what are the critical pressures that affect cerebral blood flow?

A

150 mmHg and 50 mmHg

112
Q

what is the mean artial pressure in the pulmonary circulation?

A

113
Q

at rest, what is the skeletal blood flow governed by?

A

central and baroreceptor control

114
Q

how does skeletal muscle dilate during exercise?

A

through the release of local factors like ATP, adenosine, NO, K+, and lactate

115
Q

what effect does the central command that occurs during exercise have on the blood vessels?

A

it will cause an increase in the sympathetic outflow- this causes constriction of vein and constriction of the splanchnic and renal arterioles

116
Q

what effect do the local responses that occur during exercise have on the blood vessels?

A

it causes an increase in vasodilator metabolites- so there will be a dilation of skeletal muscle arterioles and there will be a decreased in TPR

117
Q

what causes constriction of the blood vessels in the skin?

A

constriction is induced by the alpha-1 adrenergic receptors (sympathetics)

118
Q

what happens to the central sympathetics in the skin as body temperature rises?

A

the central sympathetic activation are inhibited to induce vasodilation of arterioles

119
Q

what does trauma to the skin cause release of?

A

histamine

120
Q

what effect does histamine have in the skin?

A

it produces a triple response in skin: a red line, a red flare, and a wheal (local edema)