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bioregulatory systems 🦠 > microcirculation > Flashcards

microcirculation Flashcards

1
Q

what does each individual organ have

A

it’s own microcirculation

which branches off the main artery an rejoins to main vein

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2
Q

what does the 1st order arteriole do

A

lots of smooth muscle
deliver blood to capillaries (where exchange takes place) across organ/tissue
goes to venule > drains to main vein

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3
Q

what is the overall aim of the cardiovascular system

A

to get adequate blood flow through the capillaries

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4
Q

what is blood flow rate

A

volume of blood passing through a vessel per unit time

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5
Q

what is Darcy’s law

A

fluid circuit
change in pressure gradient = flow rate x resistance
Q = pressure gradient / resistance

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6
Q

equation for pressure gradient (change in P)

A

pressure gradient = pressure A - pressure B

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7
Q

what is flow rate directly proportional to

A

pressure gradient

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8
Q

what is flow rate inversely proportional to

A

resistance

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9
Q

what is the definition of resistance

A

hindrance to blood flow due to friction between moving fluid and stationary vascular walls

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10
Q

what is the equation for resistance

A

R = 8Ln/pi r^4
vessel length = L
vessel radius = r halving the radius decreases the flow 16 times
blood viscosity = n

only the radius really changes minute to minute - the rest are fairly constant

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11
Q

what happens to pressure gradient and flow rate when increased BP

A

pressure gradient goes up

flow rate goes up

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12
Q

what happens to resistance and flow rate with arteriolar vasoconstriction

A

resistance goes up

flow rate goes down

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13
Q

what is mean arterial pressure (number)

A

93 mmHg

pressure in arteries same amount around the body

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14
Q

what is blood flow of an organ is dependent on

A

pressure gradient

using pressure B as the pressure leaving the organ (venule)

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15
Q

if flow rate cannot be the same for each organ - what does this indicate about the resistance for each organ

A

considering pressure entering and leaving are the same for each organ - the resistance must change significantly
without this pressure difference, blood would not reach capillary beds

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16
Q

what does vasoconstriction do to radius, resistance and flow rate

A

radius decreases
resistance increases
flow rate decreases
(contraction)

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17
Q

what does vasodilation do to radius, resistance and flow rate

A

increase radius
decrease resistance
increase flow rate
(relaxation)

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18
Q

what does vascular tone mean

A

partial constriction of arteriolar smooth muscle
this way you can either constrict further or dilate (if completely dilated then you can only constrict) -
in a state of partial constriction you can both dilate and constrict to increase or decrease blood flow

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19
Q

what are 2 reasons why radii of arterioles are adjusted independently

A

1) to match blood flow to the metabolic needs of specific tissues (depending on bodys momentary needs)
2) to help regulate systemic arterial blood pressure

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20
Q

describe ACTIVE HYPERAEMIA

A

regulated by intrinsic controls and is independent of nervous or endocrine stimulation
ACTIVE HYPERAEMIA
1) tissue is doing more
2) using more oxygen
3) generates metabolites (influences and is detected by arterioles)
4) arterioles dilate

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21
Q

describe MYOGENIC AUTOREGULATION

A

MYOGENIC AUTOREGULATION
1) damage to tissue
2) leakage of fluid
3) ice pack/decreased blood temp
4) vasoconstriction - diverting blood away from cold area to preserve body temp
increased stretch (distension) due to high BP > myogenic autoregulation

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22
Q

use exercise as an example to describe matching blood flow to meet demands

A

perfusion pressure - pressure through tissue bed

1) start exercise
2) pressure increases (good in some tissue but in most = not)
3) increased pressure leads to increased flow to that tissue
4) immediate increase in flow stretches arterioles
5) the arterioles respond to physical stretch
6) cause local constriction called AUTOREGULATION to bring the pressure/flow down

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23
Q

equation for blood pressure

A 
cardiac output (Q) = blood pressure (MAP) / total peripheral resistance (TPR)
so 
blood pressure (MAP) = cardiac output (Q) x total peripheral resistance (TPR)
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24
Q

definition of cardiac output

A

amount of blood flowing through system

25
Q

definition for total peripheral resistance

A

total resistance in every arteriole in the body

26
Q

equation to calculate MAP

A

SBP + 2(DBP) all / 3

27
Q

equation for cardiac output

A

cardiac output = SV x HR

28
Q

equation for stroke volume

A

SV = end diastolic - end systolic

29
Q

how do arterioles regulate systemic arterial blood pressure

A

regulated by extrinsic controls which travel via nerves or blood and are usually centrally coordinated

  • neural
  • hormonal
30
Q

describe neural methods for arterioles to help regulate systemic arterial blood pressure

A

cardiovascular control centre in the medulla
can cause vasoconstriction
eg lost a lot of blood > need to get blood pressure back up > force multiple tissue beds to constrict at the same time > increased TPR > increased BP

31
Q

describe hormonal methods for arterioles to help regulate systemic arterial blood pressure

A

brain can send signals to endocrine tissues/glands - to release vasoconstrictors
vasopressin/ADH
angiotensin 2
adrenaline/noradrenaline

32
Q

what is the purpose for capillaries and what are it’s measurements

A

the delivery of metabolic substrates to the cells of the organism (ultimate function of the cardiovascular system)
7 micrometres in diameter
1 micrometre in cell width

33
Q

why is the highly branched structure of capillaries important

A

it is close to tissues/organs
ideally suited to enhance diffusion - Fick’s Law
minimise diffusion distance
maximise the SA and time for diffusion

34
Q

do highly metabolically active tissues have more dense or less densely capillary networks

A

more dense!

35
Q

density of capillaries in skeletal muscle

A

100 cm2/g

36
Q

density of capillaries in myocardium/brain

A

500 cm2/g

37
Q

density of capillaries in lung

A

3500 cm2/g

you want capillaries to be as close to air for diffusion

38
Q

what can some tissues do to direct blood away from less important tissues

A

they can constrict to try and direct blood away from less important tissues to areas that need more eg gut constriction

39
Q

what are the 3 types of capillary structure

A

continuous
fenestrated
discontinuous

40
Q

what structure do most capillaries have

A

continuous structure - things that are really small - can get through H2O filled gap junctions eg sodium ions or water
bigger molecules have to diffuse or be moved by transporters eg glucose
other structures = fenestrated = bigger gaps > allow glucose to pass through and other bigger molecules
discontinuous structure = huge gaps > eg liver > drugs can pass through to liver and get metabolised by liver
also seen in bone marrow and spleen > for WBC to move in and out of cell

41
Q

what is the blood brain barrier

A

capillary structure but no H2O gap junctions
IMPENETRABLE CAPILLARY STRUCTURE
anything remotely water soluble needs transporter
TIGHTER CONTROL

42
Q

what is bulk flow

A

a volume of protein free plasma filters out of the capillary, mixes with the surrounding interstitial fluid (IF) and is reabsorbed
pressure forcing blood through capillaries (with water filled gap junctions) > fluid is forced out of these junctions and enters tissue

43
Q

what pressure draws fluid back in

A

oncotic pressure draws fluid back in

44
Q

what does osmotic force do

A

draws fluid back in

45
Q

what kind of a force is hydrostatic force

A

it is a pushing force

46
Q

what kind of a force is oncotic force

A

a pulling force

47
Q

what is Starling’s hypothesis

A

needs to be balanced else you’ll be decreasing blood volume

48
Q

describe the forces and therefore net movement of fluid through the journey of a capillary

A

hydrostatic pressure at the start of arteriole is high and drops as it moves down but fluid is still being forced out
oncotic pressure is constant
net pressure - due to high hydrostatic pressure at the start = massive net loss of fluid > as hydrostatic pressure drops then oncotic pressure is dominant and fluid moves back in

49
Q

what is ultrafiltration

A

if pressure inside the capillary is greater than in the IF then ultrafiltration occurs

50
Q

what is reabsorption

A

if inward driving pressures are greater than outward pressure across the capillary then reabsorption occurs

51
Q

is ultrafiltration more effective than reabsorption

A

yesssssss

net loss of fluid into tissues from the blood

52
Q

what is the role of lymphatic system

A

needs to bring the loss of fluid back otherwise blood volume will keep decreasing

53
Q

describe the lymphatic system

A

wherever there is a capillary there is a lymphatic capillary too
fluid loss forced out of the blood drains into lymphatic > drains back to major lymphatics and returns to blood

54
Q

what do lymph nodes/glands do

A

respond to bacteria/virus in the fluid that is returning to blood and triggers immune response (eg lymphocytes)

55
Q

is there a pump to induce flow of lymphatics

A

no
requires skeletal muscle forcing lymphatics back up the leg
requires negative pressure in the lungs to draw fluid up

56
Q

where is drainage

A

right lymphatic duct and thoracic duct and right and left subclavian beins

57
Q

how many L per day are returned

A

3

58
Q

what happens if the rate of production is greater than the rate of drainage

A

oedema ensures

59
Q

what happens if there is parasitic blockage of lymph nodes

A

elephantiasis

bioregulatory systems 🦠 (54 decks)

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