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HLSC 128 > Vascular Physiology > Flashcards

Vascular Physiology Flashcards

1
Q

Non-conditioning organs

A

heart, skeletal muscles

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2
Q

The vascular tree consists of…

A

arteries- carry blood from heart to tissues

arterioles- smaller branches of arteries

capillaries- smaller branches of arterioles that perform all exchanges with surrounding cells

venules- formed when capillaries rejoin and return blood to heart

veins- formed when venules merge and return blood to heart

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3
Q

Blood vessel walls are composed of alternating layers of ..

A

connective tissue (elastic and collagen fibers), smooth muscle and epithelial cells

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4
Q

Outermost layer of blood vessel

A

tunica externa/adventitia

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5
Q

Middle layer of blood vessel

A

tunica media

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6
Q

Innermost layer of blood vessel

A

tunica intima

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7
Q

What does blood flow depend on?

A

pressure in vascular system and resistance developed in vascular system

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8
Q

flow rate of blood

A

the volume of blood passing through a blood vessel per unit of time

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9
Q

pressure gradient

A

pressure difference between the beginning and end of a vessel (H–>L)

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10
Q

resistance

A

measure of opposition to blood flow through a vessel

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11
Q

what causes resistance

A

friction between moving fluid/blood against the stationary vessel wall

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12
Q

resistance to blood flow is dependent on 3 factors..

A
  1. blood viscosity (fluid dependent)
  2. vessel length (vessel dependent)
  3. vessel radius (vessel dependent)
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13
Q

Blood viscosity

A

friction between the molecules of a flowing fluid

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14
Q

Blood viscosity is determined by..

A

number of RBCs

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15
Q

relationship between #RBCS, friction, viscosity, resistance and blood flow

A

more RBCS= more friction= more viscous= greater resistance= less blood flow

less RBCs= less friction= less viscous= less resistance= more blood flow

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16
Q

Is blood viscosity important to controlling resistance?

A

No, relatively constant

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17
Q

relationship between vessel length, SA, resistance, blood flow

A

longer vessel= greater SA= more resistance= less blood flow

shorter vessel= less SA= less resistance= more blood flow

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18
Q

Is vessel length important to controlling resistance?

A

No- not a variable factor (cannot control it)

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19
Q

relationship between vessel radius, resistance and blood flow

A

bigger radius= less resistance= more blood flow

smaller radius= more resistance= less blood flow

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20
Q

Is vessel radius important to controlling resistance?

A

YES- it is a major determinant of resistance to flow, major variable

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21
Q

arteries 2 functions

A
  1. serve as ‘rapid-transit passageways’ for blood from the heart to the organs
  2. act as a ‘pressure reservoir’ to provide a driving force for blood when heart is relaxing
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22
Q

collagen fibers

A

provide tensile strength, temporarily expand without damage

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23
Q

elastin fibres

A

provide elasticity to arterial walls

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24
Q

systolic pressure

A

maximum (peak) pressure is exerted in the arteries when blood is ejected into them during cardiac systole

heart contract –> increase blood to arteries

averages 120mmHg

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25
Q

diastolic pressure

A

minimum (less) pressure in arteries when blood is draining off into vessels downstream during diastole

averages 80mmHg

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26
Q

Pulse pressure

A

pressure difference between systolic and diastolic pressure

40mmHg

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27
Q

Mean Arterial Pressure (MAP)

A

average pressure driving blood forward into the tissues throughout the cardiac cycle

=diastolic pressure + 1/3 pulse pressure = 93mmHg

=cardiac output x total peripheral resistance

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28
Q

2 criteria about MAP

A

1) must be high enough to ensure sufficient driving pressure

2) must not be SO high, it creates hard work for the heart, causing a rupture in the small blood vessels in the brain (capillaries cannot withstand high pressure because they are not elastic and are instead narrow and single celled)

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29
Q

Muscular arteries

A
  • arteries deliver blood to specific organs
  • contains a thick, smooth muscle layer in tunica media (very active in vasoconstriction and vasodilation)
    -can play major role in blood pressure regulation
30
Q

Arterioles

A
  • major resistance vessels
  • highly muscular
  • exist within organs
31
Q

The radius of arterioles supplying individual organs can be adjusted independently to…

A
  • distribute CO among systemic organs, depending on the body’s momentary needs
  • help regulate arterial blood pressure
32
Q

Arteriole wall contains..

A
  • very little elastic connective tissue
  • have a thick layer of smooth muscles (richly supplied by sympathetic nerve fibers)
33
Q

vasoconstriction

A

narrowing of a vessel

34
Q

vasodilation

A

enlargement in circumference and radius of the vessel

35
Q

relationship between vasoconstriction, resistance and blood flow

A

vasoconstriction= contraction circular smooth muscle in arteriolar wall= increased resistance= decreased blood flow

36
Q

What is vasoconstriction caused by

A
  • increased myogenic activity
  • increased oxygen
  • decreased carbon dioxide and other metabolites
    -increased endothelin
  • increased sympathetic stimulation
  • vasopressin, angiotensin II, cold
37
Q

relationship between vasodilation, resistance and blood flow

A

vasodilation= decreased contraction of circular smooth muscle in the arteriolar wall= decreased resistance= increased blood flow

38
Q

What is vasodilation caused by

A
  • decreased myogenic activity
  • decreased oxygen
  • increased carbon dioxide and other metabolites
  • increased nitric oxide
  • decreased sympathetic stimulation
  • histamine release, heat
39
Q

vascular tone

A

arteriolar smooth muscle displays a state of partial contraction

40
Q

2 factors are responsible for vascular tone

A

1) myogenic (self-induced) activity of smooth muscle

2) sympathetic fibres continually release norepinephrine

41
Q

fraction of total CO delivered to each systemic organ depends on..

A
  • number and calibre of the arterioles supplying that organ/area
  • extent of vascularization of organ/area
  • differences in the resistance offered by the arterioles supplying organ
42
Q

Active hyperemia

A

increased metabolic activity of organ= decreased oxygen, increased metabolites in organ interstitial fluid= arteriolar dilation in organ= increased blood flow to organ

43
Q

endothelial cells

A
  • release chemical mediators that play a vital role in locally regulating arteriolar calibre
  • release locally acting chemical messengers in response to chemical changes in their environment
  • among best studied local vasoactive mediators is NO and endothelin
44
Q

Factors affecting arteriolar radius and therefore total peripheral resistance

A

local(intrinsic) control and extrinsic control

45
Q

Local (intrinsic) control

A

local changes acting on arteriolar smooth muscle in the vicinity

46
Q

Examples/types of local controls

A
  • heat,cold application
  • response to shear stress
  • myogenic responses to stretch
  • histamine release (involved with injuries and allergic responses)
  • local metabolic changes in oxygen and other metabolites
47
Q

Extrinsic control

A

important in regulation of blood pressure

48
Q

Examples/types of extrinsic controls

A
  • vasopressin (hormone important in fluid balance, exerts vasoconstrictor effect)
  • angiotensin II (hormone important in fluid balance, exerts vasoconstrictor effect)
  • epinephrine and norepinephrine (hormones that generally reinforce sympathetic nervous system)
  • sympathetic activity (exerts generalized vasoconstrictor effect)
49
Q

capillaries

A
  • maximized surface area and minimized diffusion distance (capillaries lie close to cells)
  • slow velocity through capillaries allows adequate time for the exchange of materials
50
Q

how water-soluble substances, lipid-soluble and proteins pass through capillary wall

A
  • water soluble: through water-filled gaps that lie at junctions between cells
  • lipid-soluble: dissolving in a lipid bilayer barrier
  • proteins: vesicular transport
51
Q

lymphatic system

A
  • extensive network of one-way vessels
  • provides accessory route by which fluid can be returned from interstitial spaces to the blood
52
Q

functions of lymphatic system

A
  • return of excess filtered fluid
  • defense against disease- lymph nodes have phagocytes that destroy bacteria filtered from interstitial fluid
  • transport of absorbed fat
  • return of filtered protein
53
Q

Oedema

A

swelling of tissues, occurs when too much interstitial fluid accumulates

54
Q

causes of oedema

A
  • reduced concentration of plasma proteins e.g. kidney disease, liver disease, loss of proteins from burned skin
  • increased permeability of capillary wall e.g. allergic reaction
  • increased venous pressure (esp in pregnancy)
  • blockage of lymph vessels e.g. filariasis and elephantiasis
55
Q

Veins large ___ offers little resistance to blood flow

A

Veins large radius offers little resistance to blood flow

56
Q

Veins also serve as …

A

blood reservoir- ability to store large amounts of blood

57
Q

Veins:
- walls are ___ than arteries
- ___ smooth muscle, ___ elasticity, __collagen than elastin
- ___ resistance
- ___ cross-sectional area due to ___ in numbers than arteries

A

Veins:
- walls are thinner than arteries
- little smooth muscle, little elasticity, more collagen than elastin
- low resistance
- less cross-sectional area due to less in numbers than arteries

58
Q

Venous return

A

driving pressure from cardiac contraction

59
Q

Sympathetic stimulation causes ___, which ___ venous return

A

Sympathetic stimulation causes vasoconstriction, which elevates venous return

60
Q

primary determinants of blood pressure

A

cardiac output, total peripheral resistance

61
Q

Cardiac output (CO)

A

heart rate (HR:beats per minute) x Stroke volume (SV: blood volume ejected with each beat)
OR
CO= HR x SV

62
Q

baroreceptors

A

special nerve cells or receptors that sense blood pressure, by the way that the walls of the blood vessels stretch. That information is sent from the baroreceptors to the brain to help keep blood pressure balanced

The baroreceptors send signals to the brain and the signals are interpreted as a rise in blood pressure

63
Q

Baroreceptors and MAP

A
  • number of action potential increases when MAP increases
  • number of action potential decreases when MAP decreases
64
Q

ANS on heart function

A

Parasympathetic
- vagus nerves that release acetylcholine to atria never ventricles

Sympathetic
- thoracic spinal nerves/bloodstream that release norepinephrine and epinephrine to both atria and ventricles

65
Q

less sympathetic input= ___ blood vessels
more sympathetic input = ___ blood vessels

A

less sympathetic input= dilated blood vessels
more sympathetic input = constricted blood vessels

66
Q

Circulatory shock(s) occurs when..

A

blood pressure falls so low that adequate blood flow to the tissues can no longer be maintained

67
Q

4 main types of circulatory shock (s)

A
  1. hypovolemic (“low volume”) shock
  2. cardiogenic (“heart produced”) shock
  3. vasogenic (“vessel produced”) shock
  4. neurogenic (“nerve produced”) shock
68
Q

Hypovolemic shock

A

1) severe hemorrhage or excessive vomiting, diarrhea, urinary losses, etc.
2) loss of fluids derived from plasma
3) loss of blood volume
4) decrease cardiac output
5) decreased MAP –> circulatory shock

69
Q

Cardiogenic shock

A

1) weakened heart
2) decreased cardiac output
3) decreased MAP –> circulatory shock

70
Q

Vasogenic shock

A

1) (a) septic shock or (b) anaphylactic shock
2 (a) vasodilator substances released from bacteria, (b) histamine released in severe allergic reaction
3) widespread vasodilation
4) decreased peripheral resistance
5) decreased MAP –> circulatory shock

71
Q

Neurogenic shock

A

1) decreased sympathetic nerve activity
2) loss of vascular tone
3) widespread vasodilation
4) decreased peripheral resistance
5) decreased MAP –> circulatory shock

HLSC 128 (7 decks)

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