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Cardiovascular > Local regulation of blood flow - supply and demand > Flashcards

Local regulation of blood flow - supply and demand Flashcards

1
Q

haemodynamics

A

physical study of flowing blood and all the solid structures through which it flows

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2
Q

in poiseuille formula Q( flow) is proportional to what

A

change in pressure x vessel radius to the power of 4 divided by /////
blood viscosity x vessel length

lood flows from higher pressure system largest being arotia down to lower pressure in capillaries and then to lowest point in the vena cava.

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3
Q

what are the 4 physical determinants of blood flow through the vascular system

A

pressure change
vessel radius
blood viscosity
vessel length

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4
Q

As fluid becomes thicker (viscosity increases), flow decreases in proportion
What conditions may result in increased blood viscosity

A 
Polycythemia 
Hypercholesterolaemia
Diabetes
Smoking, alcoholism, severe dehydration, diuretics
(Anaemia can reduce blood viscosity)

Q=1/n
Flow is inversely proportional to the viscosity of the fluid
Moderate anaemia can actually increase tissue oxygen delivery by lowering blood viscosity and increasing flow through the vascular bed
Transfusions of cold, concentrated red blood cells run slowly

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5
Q

which factor is most important in the regulation of blood flow?

A

vessel radius

this causes the resistance

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6
Q

What property of the vasculature determines vessel radius?

A

Vascular smooth muscle tone (vasoconstriction/dilatation)

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7
Q

A change in vascular tone of which vessel type is the most influential in regulating blood flow to tissues/organs?

A

Arterioles are the main sites of resistance to blood flow within the vascular system

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8
Q

Arterioles have a thick layer of smooth muscle (tunica media) in their walls, highly innervated by what

A

by sympathetic nerve fibres

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9
Q

what arterioles vasoconstriction what happens to resistance and blood flow to the capillaries

A

resistance goes up and blood flow to the capillaries decreases

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10
Q

in the regulation of blood flow what two mechanisms controls whole body circulation

A

neurological - autonomic NS

Humoral via angiotensine II , vasopressin , adrenaline, atrial natriuretic peptide

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11
Q

in the regulation of blood flow what mechanism controls regional/ organ blood flow

A

Local(metabolic and myogenic)

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12
Q

what type of receptor does adrenaline have a greater affinity for creating what effect

A

Beta-2 so vasodilation

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13
Q

What type of receptor does nor-adrenaline have a greater affinity for creating what effect

A

Alpha-1 so vasoconstriction - there are no alpha-1 receptors however in cerebral arteriolar smooth muscle

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14
Q

A high dose of adrenaline is used in clinical settings to do what?

A

increase blood pressure through vasoconstriction

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15
Q

how is the increase of blood pressure achieved

A

Through binding to both α1 and β2 adrenergic receptors on vascular smooth muscle

Adrenaline has higher affinity for β2 receptors but there are more α1 receptors overall across the vascular bed, so a high dose of adrenaline leads to overall vasoconstriction and an increase in arterial blood pressure. Physiological levels of adrenaline cause vasodilatation through binding to β2 receptors within skeletal muscle vascular beds, decreasing blood pressure.

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16
Q

obviously cell respiration and metabolic demand goes up so Lowered partial pressure of oxygen
this triggers release of NO what does this do

A

vasodilator - relax underlying smooth muscle

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17
Q

what is active hyperaemia

A

caused by increased of blood flow to organs - blood vessels widen to increase supply of blood. - local intrinsic mechanism of increasing blood flow to tissues to meet metabolic demand

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18
Q

what does NO do

A

Local chemical and physical changes due to increased metabolic demand
Increased shear stress on endothelium

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19
Q

what does endothelin do

and what stimulates and inhibits it

A

A potent vasoconstrictor
Stimulated by angiotensin II, vasopressin
Inhibited by NO

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20
Q

what do vascular endothelia growth macros do

A

promote angiogenesis - Long-term adaptation to decreased blood flow to a tissue

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21
Q

the intrinsic myogenic response is called what

A

auto-regulation - important in kidneys

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22
Q

vascular tone is controlled by 3 influences yes or no

A

Neurogenic (sympathetic NS)
Humoral (vasoactive substances)
Local (intrinsic) mechanisms

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23
Q

Local/intrinsic control of blood flow includes what

A

Active hyperaemia – responds to changes in demand

Autoregulation – responds to changes in supply

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24
Q

when is local control of blood flow most important

A

local control of blood flow is the most important mechanism in cerebral, coronary, renal, pulmonary & exercising skeletal muscle vascular beds

25
functions of cardiovascular system
Delivery of oxygen and nutrients to tissues and removal of waste products Distributes hormones fluids , electrolytes Immune function Thermoregulation Consists of pump ( heart) pipes ( blood vessels) and a carrier ( blood)
26
what circulatory system exists at lower pressure
pulmonary - 25/10mmHg lower resistance to
27
what is the mean arterial blood pressure - MABP - approximate to diastolic +1/3 of the difference between systolic and diastolic pressure ( pulse pressure)
AROUND 87 diastolic normally twice as long elastic ompianc allows them to take blood veins share the largest amount of blood
28
total peripheral resistance TPR or systemic vascular resistance SVR is controlled how
by constricting or dilating muscular arteries and arterioles
29
the autonomic nervous system provides short term regulation and influences what
CO and vascular resistance
30
the humeral response through hormones and molecules provides short and long term regulation and influences what
vascular resistance and blood volume
31
where are baroreceptors found
aortic arch and carotid sinus
32
mechnaorecptors are detected where
aortic wall
33
what nerves reduce HR or BP
glossopharyngeal from carotid vagus from aortic arch increase para of heart and at same time bak though vagus increase para to SNS to decrease activity by B1 SNS via alpha1
34
hormones that cause excretion or reabsorption of sodium and water help regulate blood volume and thus blood pressure Aldosterone released from the adrenal cortex in response to decreased blood volume increase BP what does it do
increase sodium and water reabsorption in kidney
35
ADH released from posterior pituitary in repose to increase blood osmolarity increase BP what does it do
increases water reabsorption from kidneys and vasoconstriction
36
Type A and Type B peptides ( ANP and BNP ) are released in response to high volume load ( stretch) on atria and ventricles what do they do
increase sodium and water excretion from kidneys (and vasodilation)
37
beta 2 receptors cause vasodilation and have a higher density in the skull muscles and cardiac muscle vessels what hormone is best tp stimulate theses
adrenaline
38
alpha 1 receptors cause vasoconstriction and have a high density throughout the body what hormone is more sensitive to these
Noradrenaline
39
hormones that mainly act through inducing vasoconstriction or vasodilation to adjust vascular resistance and thus blood pressure and blood flow ARE angiotensin II which does what
a vasoconstrictor activated by angiotensin converting enzyme ACE within blood vessels
40
5 main types of blood vessels
arteries - elastic ones conserve pressure, muscular ones conduit vessels and distribute the blood arterioles - resistance vessels control the arterial pressure and local blood flow capillaries - exchange vessels and transfer nutrients and waste products venules veins - capacitance vessels which return blood to the heart
41
three layers of blood vessels
tunica interna/intima - innermost tunica media - middle tunica externa/adventitia- outside
42
describe the tunica internal
made of endothelia cells basement membrane convective tissue in contact with the blood
43
describe the tunica media
boundaries marked by internal and external elastic lamina smooth muscle cells elastin and collagen
44
describe the tunica external
connective tissue nerves and blood vessels exist here collagen and elastin
45
do arteries ten to have thick elastic all that resit distension and thus maintain a high pressure
yes arterioles ahem thicker walls relative to lumen so good for constricting veins have thin alls and large distensible lumens so are good for holding blood - capacitance
46
large elastic arteries such as the aorta and some main branches have many adaptations - they buffer the systolic rise in pressure and convert intermittent flow to contiouns flow and maintain blood flow and pressure during diastole. how is the artery adapted to do this
thick media containing lots of elastin fibres allowing the vessels to stretch during systole and rebound during diastole maintain the high pressure e wide lumen offers low resistance therefore pressure and velocity drop is low good conductance of blood they absorb and then propel blood through the inward elastic recoil during diastole propelling the blood forward and sustaining the high blood pressure
47
muscular Arteies distrubute flow, resit collapse eat joints and adjust the blood flow to tissues or organs how are they adapt to do this
thick smooth muscle media with fewer elastic fibres smooth muscle allows some degree of vasoconstriction or dilate to adjust the flow have a thick tunica external with loose structure and longitudinal collagen fibres too prevent retraction when cut
48
what vessel are the main site of resistance within the vascular system
arterioles - have a thick layer of smooth muscle with abundant amount of sympathetic nerve endings allowing extensive vasoconstriction via alpha 1 and vasodilation of b2 vasocnstriton increase upstream arterial blood pressure but reduces downstream blood flow to tissues
49
what is active hyperaemia
ability of arterioles to vasoconstriction/dilate rapidly and extensively allow them to adjust blood flow to tissues according to metabolic demand
50
where are nutrients and gases exchanged between the blood and tissue fluids
capillaries large cross section area endothelia cell and basement membrane more abundant in metabolically active tissue only abut 25% perfused arrest due to prescnece of precapillary sphincter and metarterioles nail fold ones RBC have to deform to fit
51
what are the 3 types of capillaries
continuous - most common in muscle skin and fat fenestrated- fluid exchange - renal glomerulus and synvoium of joints discountinuous/ sinusoid - seen liver and gaps allow red cell migration in the bone marrow)
52
in capillaries what does velocity equal
blood flow over the cross sectional area | if large slows velocity menial gas and nutrient exchange is more effective
53
what determines the fluid exchange between the capillaries and surrounding tissue fluid
opposing hydrostatic and osmotic pressures
54
describe and explain how fluid moves out and into the capillaries
hydrostatic pressure is greater than osmotic pressure at start of capillary so net movement out osmotic pressure is greater at the venule end so net movement in
55
hydrostatic pressure
flow and verse restiiacne and ia a force that pushes water out of blood vessels
56
osmotic pressure
aka colloid and oncotic pressure is determined by many by charges protein in the blood and pull water into blood vessels
57
net absorption and net filtration go to net filtration pressure
net filtration exceeds net absorption by approx 3l a day and the excess fluid is returned to circulation via the lymphatic system
58
veins have valves and act as capacitance vessels hat does this mean
stores and has blood volume - 65% skeletal muscle pump and respiratory pump aid venous return from lower half of body venoconstriction alpha 1 shunts blood from preoripjerla to central vessels to increase stroke volume like during exercise

Cardiovascular (20 decks)

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