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PSIO 259 > Blood Vessels 1 > Flashcards

Blood Vessels 1 Flashcards

1
Q

Arterioles are ___ vessels.

A

resistant

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2
Q

Arterioles connect ____ to _____ or _______.

A

arteries to capillaries or metarterioles

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3
Q

Arterioles contain ____ to regulate ____.

A

contain rings of smooth muscle to regulate radius and therefore resistance

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4
Q

Changes in arteriole radius depends on:

A

contraction state of smooth muscle in arteriole wall

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5
Q

Name 2 functions of varying arteriole radius.

A
  • controlling blood flow to individual capillary beds

- regulating MAP

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6
Q

Contraction level (radius) of arterioles is _________ of extrinsic influences.

A

independent

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7
Q

Vasoconstriction of arterioles =

A

increased contraction = decreased radius

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8
Q

Vasodilation of arterioles =

A

decreased contraction = increased radius

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9
Q

Regulation of blood flow to organs is based on ____. What is it regulated by?

A
  • based on need

- regulated by varying resistance

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10
Q

Organ blood flow =

A

MAP/organ resistance

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11
Q

What is regulated through changes in radius of arterioles?

A

vascular resistance

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12
Q

Local factors regulate radius, thereby regulating blood flow. Give 3 examples.

A
  • carbon dioxide
  • potassium
  • hydrogen ions
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13
Q

Changes associated with increased metabolic activity generally cause ______. This comes with increased levels of:

A
  • vasodilation
  • carbon dioxide
  • potassium
  • hydrogen ions
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14
Q

Changes associated with decreased metabolic activity generally cause _____. This comes with increased levels of:

A
  • vasoconstriction

- oxygen

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15
Q

What is active hyperemia?

A

increased blood flow in response to increased metabolic activity

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16
Q

Describe O2 delivery and CO2 removal in steady state.

A
  • O2 is delivered as fast as it is consumed

- CO2 is removed as fast as it is produced

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17
Q

Describe O2 delivery and CO2 removal during increased metabolic rate.

A
  • O2 is consumed faster than it is delivered

- CO2 is produced faster than it is removed

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18
Q

Describe the response to low O2 and high CO2.

A
  • vasodilation
  • increased blood flow
  • delivers more O2
  • removes more CO2
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19
Q

What is reactive hyperemia?

A

increased blood flow in response to a previous reduction in blood flow

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20
Q

What is the response when there is a blockage of blood flow to tissues?

A
  • metabolites increase
  • oxygen decreases
  • causes vasodilation
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21
Q

What is the response when the blockage of blood flow to tissue is released?

A
  • increased blood flow due to low resistance
  • metabolites removed
  • oxygen delivered
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22
Q

Describe the negative feedback for active hyperemia.

A

TISSUES
- increase metabolic rate
- increased O2 consumption and CO2 production
- decreased O2 concentration, increased CO2 concentration
LOCAL ARTERIOLAR SMOOTH MUSCLE
- increased vasodilation
- decreased resistance
- increased blood flow
- increased O2 delivery and CO2 removal
- increased O2 concentration, decreased CO2 concentration
- neg. feedback to step 3 in tissue

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23
Q

Describe the negative feedback for reactive hyperemia.

A

TISSUE
- decreased blood flow
- decreased O2 concentration, increased CO2 concentration
LOCAL ARTERIOLAR SMOOTH MUSCLE
- increased vasodilation
- decreased resistance
- increased blood flow
- increased O2 delivery, increased CO2 removal
- increased O2 concentration, decreased CO2 concentration
- neg. feedback to step 2 in tissue

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24
Q

Describe the myogenic response to changes in perfusion pressure.

A
  • change in vascular resistance in response to stretch of blood vessels in the absence of external factors
  • intrinsic control
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25
Q

What is perfusion pressure?

A

pressure gradient driving blood flow

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26
Q

Describe flow autoregulation.

A
  • myogenic response maintains blood flow through the tissue bed
  • blood flow remains constant (local control)
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27
Q

Why is myogenic response interconnected with responses?

A

due to metabolite concentration

28
Q

Describe neg. feedback for increased perfusion pressure in arteriole leading to decreased flow.

A
  • increased perfusion pressure
  • increased stretch of arteriolar smooth muscle
  • increased constriction
  • increased resistance
  • decreased flow
  • neg. feedback to increased flow
29
Q

Nitric Oxide (NO) is produced by _____ and causes ____.

A
  • endothelial cells
  • relaxes narrowed blood vessels
  • increases oxygen and blood flow
30
Q

Histamine is produced with ______ and causes _____.

A
  • inflammatory response
  • dilation of blood vessels
  • increases permeability
  • lowers blood pressure
31
Q

Endothelin-1 is produced by ______ and causes ______.

A
  • endothelial cells

- vasoconstriction

32
Q

Radius of arterioles is regulated by_______ mechanisms to control ____.

A
  • extrinsic

- MAP

33
Q

_____ innervates most arterioles.

A

SNS

34
Q

What hormones play a role in the regulation of the radius of arterioles?

A
  • epinephrine
  • vasopressin (ADH)
  • angiotensin II (part of the RAAS system)
35
Q

Sympathetic innervation of ______ ______ of arterioles

A

smooth muscle

36
Q

Smooth muscle of most arterioles (not those in brain) has __ _______ receptors.

A

α adrenergic receptors

37
Q

________ binds to α adrenergic receptors, causing _____, which increases ____ and _____.

A
  • Norepinephrine
  • vasoconstriction
  • increases TPR
  • increases MAP
38
Q

There are both ___ and _____ adrenergic receptors in arterioles.

A

α and β2

39
Q

______ binds to α and β2 receptors, causing _____ at α receptors and _______ at β2 receptors

A
  • epinephrine
  • vasoconstriction at α receptors
  • vasodilation at β2 receptors
40
Q

α and β2 receptors dominate in ____ and _____ tissue.

A

skeletal and cardiac

41
Q

Epinephrine is released by both:

A
  • SNS stimulation

- adrenal medulla

42
Q

What are the effects of epinephrine on arteriole radius in lower concentrations?

A
  • binds β2

- vasodilation

43
Q

What are the effects of epinephrine on arteriole radius in higher concentrations?

A
  • binds α and β2
  • Vasodilation in skeletal and cardiac muscle vascular beds = Decreases TPR → decreases blood pressure
  • Vasoconstriction in most vascular beds = Maintains/increases TPR → maintains blood pressure
44
Q

Dominant effect of epinephrine on arteriole radius is usually:

A

vasoconstriction (whole body)

45
Q

Distribution of blood does not increase proportionally, meaning:

A
  • 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
  • Disproportionate flow diverts blood to muscles
46
Q

Epinephrine is released from:

A

adrenal medulla

47
Q

Vasopressin (ADH) is secreted by ____ and does:

A
  • secreted by posterior pituitary
  • increases water reabsorption by kidneys, limits urine output
  • vasoconstriction
48
Q

Angiotensin II does what in plasma? What does it do overall?

A
  • precursor in plasma, interacts with vessel wall
  • vasoconstriction
  • increases TPR
49
Q

What is the purpose of capillaries?

A

site of exchange between blood and tissue

50
Q

How many capillaries per body? What is the total SA?

A
  • 10-40 billion per body
  • total SA = 600 m^2
  • most cells within 1 mm of capillary
  • 1 mm long
51
Q

What is the function of pores between endothelial cells?

A

protein-free plasma moves through pores

52
Q

Describe diffusion distance in capillaries.

A
  • 5-10 mm in diameter

- small diffusion distance

53
Q

Describe the walls of capillaries.

A
  • one cell layer
  • small diffusion barrier
  • have greatest total cross-sectional area
  • have slowest velocity of blood flow, which enhances exchange
54
Q

List the vessels from smallest to largest total cross-sectional area.

A
  • aorta
  • arteries/veins
  • arterioles/venules
  • capillaries
55
Q

What are the 4 types of capillaries?

A
  • continuous
  • fenestrated
  • discontinuous
  • sinusoids
56
Q

Describe continuous capillaries.

A
  • most other tissues
  • most common
  • small gaps between endothelial cells
  • small gaps allow small water-soluble molecules to move through
57
Q

Describe fenestrated capillaries.

A
  • kidneys, intestines
  • large gaps between endothelial cells forming pores/fenestrations (windows)
  • large gaps allow proteins, and in some cases blood cells to move through
58
Q

Describe discontinuous capillaries.

A
  • spleen, bone marrow, liver
  • transition between fenestrated to sinusoids
  • proteins and cells need to cross
  • discontinuous form sinusoids
59
Q

Describe sinusoids capillaries.

A
  • formed from discontinuous (same organs)
  • large spaces filled with blood
  • exchange between blood and tissues
  • ie. RBCs from marrow to circulation
60
Q

Describe the structure of metarterioles.

A
  • intermediate between arterioles and capillaries

- directly connect arterioles to venules

61
Q

What is the function of metarterioles?

A

function as shunts to bypass capillaries

62
Q

What do the rings of smooth muscle do on metarterioles.

A
  • at strategic locations
  • contract and relax in response to local factors
  • contract: decrease blood flow through capillaries
  • relax: increase blood flow through capillaries
63
Q

What are pre capillary sphincters?

A

rings of smooth muscle that surround capillaries on the arteriole end

64
Q

Pre capillary sphincters contract and relax in response to ____ _____ only.

A

local factors

65
Q

Contraction of pre capillary sphincters causes:

A
  • constriction of capillary

- decreased blood flow

66
Q

Relaxation of pre capillary sphincters causes:

A

increased blood flow

67
Q

What causes relaxation of pre capillary sphincters?

A

metabolites

PSIO 259 (22 decks)

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