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Physio > Chapter 14 - Blood vessels, flow, and pressure > Flashcards

Chapter 14 - Blood vessels, flow, and pressure Flashcards

1
Q

what determines flow rate

A

it’s directly proportional to the difference between the pressure at the two ends of the pipe and inversely proportional to the resistance of the pipe

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2
Q

what is bulk flow

A

flow due to pressure gradient

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3
Q

how does heart move blood

A

it creates a pressure gradient for bulk flow of blood. a gradient must exist throughout the circulatory system to maintain blood flow

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4
Q

does flow rate depend on absolute pressure

A

no it depends only on the pressure gradient

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5
Q

what is delta P for systemic circuit

A

pressure in aorta minus pressure in vena cava just before it empties into right atrium

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6
Q

what is the pressure in the aorta

A

mean arterial pressure (MAP) = 88mm Hg

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7
Q

what is pressure in vena cava

A

cenral venous pressure (CVP = 0 mm Hg

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8
Q

what does MAP provide

A

it is the overall driving force that pushes blood through systemic circuit

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9
Q

how dose pressure gradient in pulmonary circuit compare to systemic circuit

A

there is a smaller pressure gradient in pulmonary than systemic

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10
Q

what is delta P for pulmonary circuit

A

pressure in pulmonary arteries minus pressure in pulmonary veins = 15 mm HG

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11
Q

what is pulmonary arterial pressure

A

15 mm HG

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12
Q

what is pulmonary venous pressure

A

0mm HG

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13
Q

how does the amount of flow through pulmonary and systemic circuits compare

A

they are equal. While systemic pressure gradient is much higher the resistance in the pulmonary circuit is much less so it balances out

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14
Q

name 3 factors affecting resistance

A

radius of vessel (arterioles [and small arteries] can greatly change radius). Length of vessel (stays the same in a person). and viscosity of fluid (blood viscosity depends on the amount of RBCs and proteins - usually constant).

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15
Q

what is the equation for flow

A

(delta P)(pi)(r^4)/(8)(viscosity)(L)

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16
Q

what is vasoconstriction

A

decreased radius of arterioles and small arteries. leads to increased resistance

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17
Q

what is vasodilation

A

increased radius in arterioles and small arteries. leads to decreased resistance

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18
Q

what is total peripheral resistance (TPR)

A

combined resistance of all blood vessels within the systemic circuit

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19
Q

how does the equation for flow = delta P/R apply to systemic circulation

A

flow = cardiac output (CO). Delta P = mean arterial pressure (MAP). R = total peripheral resistance (TPR). CO = MAP/TPR

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20
Q

compare arteries and veins

A

arteries carry blood away from heart while veins return blood to the heart

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21
Q

describe walls of blood vessels

A

3 layers found in all vessels except capillaries. endothelium lines all blood vessels. smooth muscle layer (also containing elastin and collagen fibers). and connective tissue layer. Capillaries have only endothelium

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22
Q

what is compliance

A

a measure of the relationship between the pressure and volume changes in a blood vessel.

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23
Q

what is compliance like in arteries

A

low compliance. Small increase in blood volume causes a large increase in pressure (or a large increase in pressure causes only small degree of expansion of blood vessel wall)

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24
Q

describe blood pressure in the aorta

A

fluctuates with cardiac cycle. systolic blood pressure = maximum pressure due to ejection of blood into aorta. diastolic blood pressure = minimum pressure (not zero due to elastic recoil)

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25
Q

what does pressure in cuff higher than systolic cause

A

a fully compressed brachial artery so there are no sounds

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26
Q

what is the pressure at first sound

A

the systolic blood pressure

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27
Q

what is pressure when sound disappears

A

diastolic blood pressure

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28
Q

how is measure BP shown

A

SP/DP

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29
Q

what is pulse pressure

A

SP - DP ex. 110-70 = 40 mm Hg

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30
Q

how do you calculate MAP from measured BP

A

SP + (2xDP)/3 ex. (110 + 140)/3 = 88.3 mm Hg

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31
Q

describe arterioles

A

part of microcirculation. they connect arteries to capillaries. regulate blood flow into capillary b4ds. arterioles are resistance vessels. they can greatly change their diameter through vasoconstriction or vasodilation; arterioles are the best site to regulate resistance

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32
Q

what percentage of TPR is caused by arterioles

A

more than 60% of TPR is attributable to arterioles

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33
Q

where and how much is the largest pressure drop in vasculature

A

it is along the arterioles and it is 90 mm Hg to 40 mm Hg

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34
Q

what two things to arteriolar resistance regulate

A

blood flow into individual capillary beds and MAP

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35
Q

what does radius of arterioles depend on

A

contraction state of smooth muscle in arteriole wall

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36
Q

what is arteriolar tone

A

continuously contracted at mid-level. contraction level (radius) is independent of extrinsic influences

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37
Q

how is local blood flow regulated

A

local blood flow in individual organs/capillary beds is regulated through intrinsic (local) mechanisms

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38
Q

how is systemic arterial pressure (MAP) regulated

A

it is regulated through extrinsic mechanisms (neural, hormonal)

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39
Q

describe intrinsic control of blood flow to organs

A

regulation of blood flow to organs is based on need. regulated by varying resistance. vasulcar resistance is regulated through changes in radius of arterioles. local factors regulate radius, thereby regulating blood flow

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40
Q

describe intrinsic control of blood flow to organs based on metabolic activity

A

changes associated with increased metabolic activity generally cause vasodilation. (carbon dioxide, potassium, hydrogen ions). Changes associated with decreased metabolic activity generally cause vasoconsriction (oxygen)

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41
Q

describe active hypermia

A

increased blood flow in response to metabolic activity. Steady state: O2 is delivered as fast as it’s consumed, CO2 is removed as fast as it is produced. Increased metabolic rate: O2 is consumed faster than it’s delivered, CO2 is produced faster than its removed.

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42
Q

what is response to low O2 and high CO2

A

vasodilation and increase in blood flow thus more O2 delivered and more CO2 removed

43
Q

describe reactive hypermia

A

increased blood flow in response to a previous reduction in blood flow. Blockage of blood flow to tissues: metabolites increase and oxygen decreases, vasodilation, increased blood flow due to low resistance. When blockage is released: blood flow remains elevated until metabolites are removed, oxygen is delivered, normal concentration restored

44
Q

what is a myogenic response

A

change in vascular resistance in response to stretch of blood vessels in absence of external factors

45
Q

what is the purpose of myogenic autoregulation of blood flow

A

keep blood flow constant (autoregulation)

46
Q

describe myogenic autoregulation of blood flow

A

increased perfusion pressure increases blood flow and pressure in arterioles. increased pressure in arteriole stretches arteriole wall.stretch of vascular smooth muscle induces conraction of vascular smooth muscle (inherent property of smooth muscle). vasoconstriction decreases blood flow

47
Q

describe regulation of blood flow during exercise

A

CO increases during exercise. distribution of blood does not increase proportionally: dilation of vessels to skeletal muscle and heart increases blood flow to muscles. constriction of vessels to GI tract and kidneys decreases blood flow to these organs. So disproportionate flow diverts blood flow to muscles

48
Q

describe sympathetic control of arteriolar radius

A

sympathetic innervation of smooth muscle of arterioles. smooth muscle of most arterioles (not those in brain) has alpha adrenergic receptors. norepinephrine binds to alpha adrenergic receptors. produces vasoconstriction. increases TPR, increases MAP

49
Q

what is distribution of adrenergic receptors in skeletal and cardiac muscle

A

predominately beta 2 receptors. epinephrine causes vasoconstriction at alpha receptors and vasodilation at beta 2 receptors. epinephrine has greater affinity for beta 2 receptors and binds beta 2 in lower concentrations

50
Q

describe effects of epinephrine on arteriole radius at higher concentrations

A

binds both alpha and beta 2. this causes vasodilation in cardiac and skeletal vascular beds due to beta 2 receptors and promotes blood flow to these tissues. vasoconstriction due to alpha receptors at most vascular beds. this maintains/increases TPR, and an increase in MAP maintains systemic blood pressure

51
Q

describe hormonal control of arteriole radius and MAP

A

epinephrine: released from adrenal medula. Vasopressin (ADH): secreted by posterior petuitary, increases water reabsorption by kidneys, vasoconstriction. Angiotensin II: vasoconstriction increases TPR.

52
Q

what is the equation for MAP

A

CO x TPR

53
Q

what is the equation for CO

A

HR x SV

54
Q

what is the total equation for MAP

A

MAP = HR x SV x TPR

55
Q

what happens if MAP is less than normal

A

hypotension leading to inadequate blood flow to tissues

56
Q

what happens if MAP is greater than normal

A

hypertension leading to damaging of heart and blood vessels

57
Q

how is MAP regulated

A

through control of heart (CO) and arterioles and veins (TPR) due to both neural control and hormonal control

58
Q

describe short term regulation of MAP

A

seconds to minutes. regulates CO and TPR, involves heart and blood vessels, primarily neural control.

59
Q

describe long term regulation of MAP

A

hours to days. regulates blood volume. involves the kidneys. primarily hormonal control

60
Q

describe neural control of MAP

A

negative feedback loops: detector = baroreceptors. integration center = cardiovascular centers of brainstem. controllers = autonomic nervous system. effectors = heart and blood vessels

61
Q

describe baroreceptors

A

pressure receptors. mechanoreceptors sensitive to stretch. nerve ending of visceral afferent neurons. high pressure baroreceptors - arterial and are located in aortic arch and in the carotid sinuses. they respond to stretching due to pressure changes in arteries

62
Q

what is the integration center for blood pressure regulation

A

medulla oblongota of brainstem

63
Q

describe inputs and outputs of cardiovascular control center

A

input comes from: arterial baroreceptors, low-pressure baroreceptors, chemoreceptors, proprioceptors, and higher brain centers. Output goes to sympathetic nervous system and parasympathetic nervous system

64
Q

describe paraympathetic input into cardiovascular effectors

A

SA node (decreases HR), and AV node (decreases conduction velocity)

65
Q

describe sympathetic input into cardiovascular effectors

A

SA node (increases HR). AV node (increases conduction velocity). ventricular myocardium (increases contractility). arterioles (vasoconstriction increases resistance). Veins (vasoconstriction increases venomotor tone, lower compliance)

66
Q

what is baroreceptor reflex

A

fast neural mechanism to mediate short-term regulation of MAP

67
Q

what are detectors, afferents, integration center, efferents, and effectors of negative feedback loop to maintain blood pressure at normal level

A

detectors = baroreceptors. afferents = visceral afferents. integration center = cardiovascular control center. efferents = autonomic nervous system. effectors = heart, arterioles, and veins

68
Q

describe epinephrine control of MAP

A

released by adrenal medulla in response to sympathetic activity. increases MAP. acts on smooth muscle of arterioles (increases TPR). acts on smooth muscle of veins (increases venomotor tone). acts on heart (increases HR and SV)

69
Q

where are low pressure baroreceptors located

A

located at strategic low-pressure sites: walls of large systemic veins, walls of atria, and pulmonary veins.

70
Q

what do low pressure baroreceptors detect

A

changes in blood volume. decrease in blood volume activates receptors which trigger responses that act in parallel with the baroreceptor reflex

71
Q

where is thermoregulation mediated

A

through the hypothalamus (the bodies thermostat)

72
Q

what does an increase in core body temp stimulate

A

decrease in sympathetic activity to skin vasculature. vasodilation in skin blood vessels. increase in heart radiation to environment.

73
Q

which takes presedence during vigorous exercise: thermoregulation or baroreceptor reflex

A

thermoregulation

74
Q

describe baroreceptor reflex contribution to restoring near normal MAP during hemorrhage

A

Hemorrhage leads to decrease in blood volume - lower CO - decrease in MAP. triggers baroreceptor reflex. increases sympathetic activity. increases peripheral resistance and decreased blood flow in extremities, skin, skeletal muscles, and abdominal viscera. blood diverted to brain and heart (at expense of all else). MAP is restore and maintained at near normal levels

75
Q

describe capillary anatomy

A

10-40 billion per body. 5-10 micro meter in diameter. allows blood cells to pass in single file. Walls are single cell layer of endothelium. have greatest total cross-sectional area. have slowest velocity of blood flow which enhances exchange

76
Q

describe continuous capillaries

A

found in most organs. have narrow clefts between endothelial cells. allow passage for small water-soluble molecules between cells (exception is brain capillaries)

77
Q

describe fenestrated capillaries

A

found in intestines, kidneys, choroid plexuses, and glands. have pores (60-80 nm) that run through endothelial cells. allow more flow of solutes (including small proteins) through

78
Q

describe discontinuous (sinusoid) capillaries

A

found in liver spleen and bone marrow. have large gaps between the cells. allow for passage of whole cells

79
Q

describe metarterioles

A

structurally between capillaries and smallest arterioles.. directly connect arterioles to venules bypassing capillaries. have smooth muscle at strategic locations: contract and relax in response to local factors.

80
Q

what does metarteriole contraction cause

A

increased blood flow through capillary bed

81
Q

what does metarteriole relaxation cause

A

decreased blood flow through capillary bed

82
Q

how does lipophilic diffusion in capillaries work

A

diffusion across the membrane

83
Q

how does hydrophilic diffusion in capillaries work

A

diffusion through clefts/gaps between the cells (paracellular route)

84
Q

what is transcytosis

A

endocytosis on luminal side, exocytosis into intersitium on the other side for large macromolecules

85
Q

are capillaries permeable to water

A

yes all capillaries, including in the brain are freely permeable to water

86
Q

describe mediated transport in brain

A

in brain capillaries tight junctions do not allow solutes to pass between cells (blood-brain barrier)

87
Q

how does water move in capillaries

A

through paracellular route between the cells and through water channels in the cells

88
Q

what is filtration in capillaries

A

movement out of capillary into interstitial space

89
Q

what is absorption in capillaries

A

movement into capillary from interstitial space

90
Q

what is hydrostatic pressure

A

force generate by fluid itself (due to blood pressure inside capillary, gravity, fluid outside capillary)

91
Q

what is osmotic pressure

A

force exerted on water by non-permeating solutes: large plasma proteins (albumin, globulins, fibrinogen) and proteins in interstitial fluid

92
Q

what is capillary hydrostatic pressure at arteriole end and venous end

A

arteriole end = 38 mm Hg. and venous end = 16 mm Hg

93
Q

what is interstitial hydrostatic pressure

A

low and constant 0-1 mm Hg

94
Q

what is capillary and interstitial fluid osmotic pressure

A

capillary osmotic pressure = 25 mm Hg, constant. interstitial fluid osmotic pressure = 0-1 mm Hg, constant

95
Q

describe venules

A

smaller than arterioles. connect capillaries to veins. little smooth muscle in walls. some exchange of material between blood and interstitial fluid

96
Q

describe veins

A

large diameter, thinner walls. valves allow unidirectional blood flow: present in peripheral veins (upper and lower limbs). absent in central veins (veins in thorax and abdomen)

97
Q

describe compliance in veins

A

high compliance vessels: expand with little change in pressure. function as volume reservoir for blood. 60% of total blood volume in systemic veins at rest

98
Q

name 4 factors than influence venous pressure and venous return

A

skeletal muscle pump. respiratory pump. venomotor tone. blood volume.

99
Q

describe skeletal muscle pump

A

one-way valves in peripheral veins. when skeletal muscle contracts: squeezes on veins, increasing pressure. blood moves toward heart. blood cannot move backward due to valves. when skeletal muscle relaxes: blood flows into veins between muscles

100
Q

describe respiratory pump

A

inspiration: decreases pressure in thoracic cavity. increases pressure in abdominal cavity. pressure on veins in abdominal cavity creates pressure gradient favoring blood movement toward thoracic cavity. increases central venous pressure. increases venous return

101
Q

describe venomotor tone

A

it is smooth muscle tension in veins. an increase in venomotor tone: contraction of smooth muscle in the wall of a vein. smooth muscle in walls of veins is innervated by sympathetic nervous system. norepinephrine acting at alpha adrenergic receptors causes venous constriction. increases central venous pressure. decreases venous compliance. increases venous return

102
Q

describe blood volume as influencer of venous pressure and venous return

A

increased blood volume leads to increased venous pressure. decreases blood volume leads to decreased venous pressure

103
Q

describe the lymphatic system

A

system of vessels that collects and returns excess filtrate to circulation. lymphatic capillaries collect interstitial fluid from loose CT. lymph travels in lymphatic vessels of increasing size. lymphatic vessels resemble veins (much thinner and with more valves). lymphatic vessels go through one or more lymph nodes (full of immune cells). lymphatic vessels merge to form larger trunks, which merge to form two ducts that deliver lymph to the great veins at base of neck (brachiocephalic veins). lymph flows from tissues toward heart (one-way system)

Physio (7 decks)

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