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Physiology > Regulation of Blood Flow > Flashcards

Regulation of Blood Flow Flashcards

1
Q

Cardiovascular reflexes adjust…

A

blood flow to meet immediate demand

- alters CO and/or TPR

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2
Q

Cardiovascular reflexes will monitor…

A

conditions in specific locations in cardiovascular system

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3
Q

Control mechanisms of cardiovascular reflexes are…

A

systemic

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4
Q

Cardiovascular reflex center is located in the…

A

medulla oblongata

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5
Q

CV reflex center gets input from…

A
  • peripheral baroreceptor and chemoreceptors

- high centers

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6
Q

CV reflex center outputs via changes to…

A

PNS and SNS to heart and blood vessels

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7
Q

Hypothalamus provides _____ input to CV center

A

behavioral and thermal

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8
Q

Examples of behavioral input:

A
  • fear
  • anger
  • pain
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9
Q

Behavioral input leads to…

A
  • increase of SNS output
  • decrease of PNS output
  • increase in heart rate
  • increase in SV
  • increase in MAP
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10
Q

Behavioral input produces…

A
  • venoconstriction to increase VR and CO

- vasoconstriction to increase TPR

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11
Q

Behavioral input is a stress response designed to…

A

provide body with increased available O2 and deliver to appropriately respond to stress

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12
Q

Thermal input comes from…

A

thermoreceptors in skin and blood perfusing hypothalamus

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13
Q

Thermal input leads to ____ output…

A

SNS output to peripheral blood vessels of skin

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14
Q

Thermal input will lead to the…

A

redistribution of blood flow

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15
Q

What happens with cold input?

A
  • increased SNS output to skin
  • constricts surface vessels
  • reducing flow
  • limiting heat loss
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16
Q

What happens with warm input?

A
  • decreased SNS output to skin
  • surface vessels dilate
  • increases surface flow
  • promoting heat loss
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17
Q

When body is stressed, it first pulls blood away from…

A

skin, GI, and reproductive system so it can flow to areas that need O2

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18
Q

Arterial baroreceptors are located in…

A

carotid sinuses and aortic arch

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19
Q

Arterial baroreceptors continuously…

A

monitor pressure in cardiovascular system

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20
Q

Arterial baroreceptors: increased MAP leads to an increase in…

A
  • pressure on vessel wall
  • vascular stretch and deformation
  • firing
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21
Q

Sensitivity of arterial baroreceptors can be…

A

altered

- ex: high BP leads to adaptation (occurs due to stiffness of sinus and/or aorta)

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22
Q

Increased firing of baroreceptors will cause the CV center to respond by…

A
  • decreasing SNS output to arterioles, which leads to decreased vasoconstriction and venoconstriction
  • increasing PNS output, which leads to increased venous compliance and decreased VR, therefore decreased EDV
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23
Q

Decreased vasoconstriction leads to…

A
  • decreased TPR
  • increased outflow into venous system
  • decreased MAP
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24
Q

Decreased venoconstriction leads to…

A
  • increased venous compliance
  • decreased VR
  • decreased EDV
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25
Q

Reflex of arterial baroreceptors causes…

A

fast changes in blood pressure in response to abrupt changes in blood volume
- orthostatic hypotension: short term drop in VR due to gravity triggers decreased firing rate of baroreceptors

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26
Q

Cardiopulmonary baroreceptors are…

A

tonically active mechanoreceptors located in R atrium and pulmonary vessels

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27
Q

Increase in volume of blood in atria or pulmonary vessels lead to…

A

increase in stretch and firing of cardiopulmonary baroreceptors

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28
Q

Increased firing of cardiopulmonary baroreceptors lead to…

A
  • decreased SNS output (especially to kidney)
  • decreased ADH
  • release of ANP from atrial myocytes
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29
Q

Cardiopulmonary baroreceptors: decreased SNS output to kidneys will…

A
  • increases renal blood flow and urine flow
  • helps to eliminate excess fluid
  • decreases blood volume
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30
Q

Cardiopulmonary baroreceptors: decrease in ADH leads to…

A
  • inhibition of release of anti-diuretic hormone from hypothalamus
  • diuresis occurs: increase urine production removes excess fluid from cardio system
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31
Q

Decreased firing of cardiopulmonary baroreceptors lead to…

A
  • increased SNS output to kidney
  • increased release of angiotensin, aldosterone, and ADH vasopressin (reabsorption at kidney)
  • helps retain salt and water by kidney
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32
Q

Peripheral chemoreceptors monitors…

A

level of O2/CO2 in blood leaving the heart

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33
Q

Peripheral chemoreceptors located in…

A

aortic and carotid bodies

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34
Q

Peripheral chemoreceptors are the primary input to..

A

respiratory center in medulla to provide respiratory adjustments
- direct input to CV center and indirect input through respiratory center

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35
Q

Increased peripheral chemoreceptors firing comes from…

A
  • increased partial pressure of CO2 in arterial blood
  • decrease in O2 pressure
  • decrease in pH of blood
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36
Q

Increased firing of peripheral chemoreceptors lead to…

A

mild increase in SNS output from CV center

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37
Q

Central chemoreceptors monitor…

A

presence of wastes in the brain, which would inhibit activity of neurons

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38
Q

Central chemoreceptors are located in…

A

medulla

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39
Q

Central chemoreceptors are directly stimulated by…

A
  • decrease of pH

- increase of CO2 pressure

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40
Q

T/F: O2 tension has a big direct effect on central chemoreceptors

A

F

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41
Q

Effect of hyperventilation on central chemoreceptors:

A
  • decreased tonic action
  • increase pH
  • decrease CO2 pressure
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42
Q

Central ischemic response is…

A

insufficient blood flow to brain

- increased firing of central chemoreceptors, which lead to massive increase in SNS

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43
Q

Overall regulatory activity is a combo of…

A

extrinsic and intrinsic factors

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44
Q

In the brain and heart, does extrinsic or intrinsic factor systems dominate?

A

intrinsic

- limited tolerance for decrease in CO2 pressure

45
Q

In the skin and splancnic (blood flow to GI), does extrinsic or intrinsic factor systems dominate?

A

extrinsic

  • regulate themselves locally during rest
  • allows body to divert flow of blood away during stress
46
Q

In skeletal muscles, does extrinsic or intrinsic factor systems domintate?

A

intrinsic

47
Q

Mean arterial pressure is sensed and corrected by…

A
  • baroreceptor reflex
  • chemoreceptor reflex
  • hormones
48
Q

Which hormones regulate mean arterial pressure?

A
  • renin-angiotensin-aldosterone (RAA) system
  • epi and norepi
  • anti-diuretic hormone (ADH)
  • atril natriuretic peptide (ANP)
49
Q

Long term regulation of blood pressure is based on…

A

vascular health and adequate circulating volume

50
Q

Decrease in vascular health leads to…

A

atherosclerosis: age and disease related changes in vascular wall

51
Q

Atherosclerosis gives a fixed…

A

volume of blood vessels and reduces ability to compensate by altering diameter

52
Q

Effects of atherosclerosis:

A
  • stiffens wall and narrows lumen
  • decrease in arterial compliance
  • contributes to elevated pulse pressure
  • reduces overall sensitivity of baroreceptors
53
Q

Circulating volume is primarily under control of…

A

kidneys and GI systems

54
Q

Kidney controls…

A

excretion and reabsorption of salt and water

55
Q

GI system mediates…

A

absorption of salt and water

56
Q

Inadequate circulation of blood volume can be corrected by…

A
  • activating thirst mechanisms
  • shifting blood volume from peripheral vascular beds to heart
  • increasing venomotor tone
  • orthostatic changes
  • reabsorption of interstitial fluid at capillaries due to changes in starling forces
57
Q

Hemorrhage, hypotension, and exercise all cause…

A

primary changes in either CO or TPR

- has to be matched by compensatory changes elsewhere

58
Q

Hemorrhage is…

A

blood loss

- abnormal change, so body has to compensate for changes not caused by altered metabolic activity

59
Q

What does a hemorrhage look like?

A
  • cutaneous veins collapsed
  • pale, moist skin
  • fast breathing
60
Q

Vital signs during hemorrhage:

A
  • decrease in arterial systolic and diastolic pressures
  • decrease in VR -> decrease in EDV and SV
  • decrease in CO = decrease in MAP
  • arterial pulse is rapid and feeble
61
Q

Response to a hemorrhage:

A

mobilize blood stored in veins and spleen to restore bp by restoring blood volume

62
Q

To fix the decrease in MAP caused by a hemorrhage, what is required?

A
  • increase in CO

- increase in TPR

63
Q

If MAP decreases but is above 60 mmHg during a hemorrhage, what can restore bp?

A

baroreceptor reflexes

64
Q

What happens when baroreceptor reflexes kick in during a hemorrhage?

A
  • decreases stretch on aortic arch and carotid sinus
  • decreases firing of baroreceptors
  • decrease in PNS
  • increase in SNS
  • increase in CO via increase in HR and SV
  • venoconstriction
65
Q

Venoconstriction leads to…

A
  • increased VR, which will increase EDV, which in turn increases SV, which finally increases CO
66
Q

If MAP decreases below 60 mmHg during a hemorrhage, what happens?

A

chemoreceptor reflexes, which leads to increase in firing

67
Q

What happens when chemoreceptor reflexes kick in during a hemorrhage?

A
  • increased SNS

- respiration stimulated leads to ancillary pump increasing VR

68
Q

If MAP decreases below 40 mmHg during a hemorrhage, what happens?

A

cerebral ischemia responses lead to massive increase in SNS

69
Q

Increase in MAP leads to neural changes via increase in…

A
  • HR
  • cardiac contractility
  • TPR
  • venoconstriction
70
Q

Prolonged response to hemorrhage occurs over…

A

12-24 hours to increase blood volume

71
Q

Ways to increase blood volume during a hemorrhage:

A
  • decreasing capillary hydrostatic pressure
  • thirst mechanism
  • release of endogenous constrictor substances
72
Q

Decreasing capillary hydrostatic pressure increases blood volume during a hemorrhage by…

A

increasing reabsorption of fluid from ISF

73
Q

The thirst mechanism increases blood volume during a hemorrhage by…

A

increasing fluid ingestion and absorption

74
Q

Examples of endogenous constrictor substances:

A
  • epi from adrenal medulla (SNS)
  • vasopressin (ADH): decreases urine production
  • renin-angiotensin system (RAS) ANG II
75
Q

Function of renin-angiotensin system (RAS) ANG II:

A
  • potent vasoconstrictor
  • stimulates release of aldosterone
  • renal conservation of salt and water
  • decreases urine production
76
Q

A severely prolonged response to a hemorrhage occurs over…

A

24 H

77
Q

What happens during a severely prolonged response to a hemorrhage?

A
  • synthesis of plasma proteins by liver

- stimulation of erythropoeisis in bone marrow to increase hematocrit

78
Q

What happens when hemorrhage stops but MAP drops below 50 mmHg?

A
  • can cause death due to circulatory shock
  • severe tissue damage, irreversible circulatory collapse and death
  • positive feedback downward spiral
79
Q

What are the downstream effects of hypotension due to hemorrhage?

A
  • cardiac failure
  • CNS depression
  • kidney failure
  • aberrations of blood clotting
80
Q

CNS depression due to hemorrhage leads to..

A
  • decreased cerebral blood flow

- acidosis

81
Q

Shock is the failure of the cardiovascular system to…

A

deliver enough O2 and nutrients to meet cellular metabolic needs

82
Q

What are the four types of shock?

A
  • hypovolemic
  • cardiogenic
  • vascular
  • obstructive
83
Q

Shock homeostatic compensation:

A
  • activation of renin-angiontensin-aldosterone system
  • secretion of ADH
  • release of local vasodilators
84
Q

Orthostatic hypotension:

A

low blood pressure resulting from failure to return blood volume from veins to heart

85
Q

T/F: orthostatic hypotension is true blood loss

A

F, it’s just a change in distribution

86
Q

Orthostatic hypotension has a ____ effect

A

gravitational

- occurs when shifting from prone (lying down) to upright or standing for long time

87
Q

What happens via orthostatic hypotension during standing?

A
  • superficial veins in neck collapse
  • can induce fainting
  • lack of muscular pump -> decrease in VR
88
Q

Orthostatic hypotension can be completely compensated for via…

A

mechanisms initiated by baroreceptors

89
Q

Thermal effect:

A
  • pooling of blood in dependent vessels

- interferes with compensatory vasomotor reaction and absence of muscle activity

90
Q

Thermal effect is caused by…

A
  • warm ambient temp: induces vasodilation, so more blood moves into venous system
  • heavy clothing: prevents heat loss
91
Q

Exercise is a normal change in…

A

metabolic activity

92
Q

Cardiovascular adjustments due to exercise is a combo of…

A

neural and local (chemical) factors

93
Q

Neural factors for cardiovascular adjustments:

A
  • central command: cerebrocortical activity of SNS
  • mental anticipation increases SNS and decreases PNS output
  • not controlled by baroreceptor reflex
94
Q

What increases due to neural factors in cardiovascular adjustments?

A
  • HR
  • myocardial contractibility
  • TPR
  • MAP prior to muscle activity
95
Q

Reflexes for cardiovascular adjustments originate in…

A

skeletal muscle

- alters SNS output via mechanoreceptors by stretch and tension

96
Q

Local/humoral factors causes cardiovascular adjustments in three ways:

A
  • K+ released by contracting muscle
  • adenosine and decrease in tissue pH
  • circulating epi
97
Q

In local/humoral factors in cardiovascular adjustments, K+ acts as…

A

vasodilator

- partly responsible for initial decrease in vascular resistance

98
Q

In local/humoral factors in cardiovascular adjustments, adenosine sustains…

A

vasodilation in blood vessels of skeletal muscle as exercise is sustained

99
Q

In local/humoral factors in cardiovascular adjustments, circulating epi contributes to vasodilation by…

A

binding to beta receptors on blood vessels w/in skeletal muscle bed

100
Q

When there is an anticipation of mild to moderate exercise, ____ is increased and ____ is decreased

A

SNS, PNS

101
Q

When SNS is increased for mild to moderate exercise, what happens?

A
  • decreased blood flow to viscera
  • increase in CO
  • increase in blood flow to active muscle
  • increase in myocardial flow
102
Q

What is blood flow like in the skin during mild to moderate exercise?

A
  • decreases to skin at first

- increases as body temp increases

103
Q

During mild to moderate exercise, there is marked…

A

capillary recruitment

  • only small % of capillaries perfused at rest
  • more perfused during exercise
104
Q

During mild to moderate exercise, there is an increase in…

A
  • hydrostatic pressure in capillaries: water and solutes move into ISF
  • tissue hydrostatic pressure: fluid carries away by lymphatics
105
Q

Blood volume loss is limited during mild to moderate exercise by…

A
  • increase in tissue hydrostatic P
  • increase in plasma osmolarity
  • decrease in urine formation
106
Q

During severe exercise, what beings to fail?

A

compensation mechanisms

107
Q

During severe exercise, there is an increase in _____ and a decrease in _____

A
  • SNS, which leads to vasoconstriction so body temp increases
  • tissue and blood pH due to increase in lactic acid and CO2 production
108
Q

Limits of exercise performance:

A
  • pump limitation
  • O2 supply to muscle
  • regular exercise improves cardiovascular performance
109
Q

Max effective HR is…

A

180 beats/min

Physiology (33 decks)

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