Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

cardiovascular system year 1 > exchange and flow in the peripheral circulation > Flashcards

exchange and flow in the peripheral circulation Flashcards

1
Q

features of capillaries

A

specialised for exchange
lots of them
thin walled - small diffusion barrier
small diameter (big SA:vol ratio)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what are the 3 types of capillaries

A

continuous
fenestrated
discontinuous

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

continuous capillaries

A

no clefts (between cells) or pores (within cells)
e.g. brain
for the blood brain barrier, protect the brain from blood K conc

clefts only
e.g. muscle
allows some exchange

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

fenestrated capillaries

A

clefts and pores

e.g. intestine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

discontinuous capillaries

A

clefts and massive pores

e.g. liver

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

types of exchange

A

diffusion (majority of exchange)
carrier mediated exchange
bulk flow

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

where does exchange occur from capillary to cell

A

between capillary and ECF, between cell and ECF

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

how does oxygen diffuse

A

down its conc grad

it is lipophilic -no barriers to diffusion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

features of diffusion

A

self regulating - if the cell starts using more oxygen there is a larger conc grad so more is supplied
non-saturable - there is no point where oxygen transport is at its max
non-polar substances across membrane
polar substances through clefts/channels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

describe an example of carrier mediated transport

A

glucose transport
in the brain - glucose is trapped within the capillaries but is highly needed by the brain so a protein transporter is required to move the glucose across

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

features of bulk flow

A

fluid transport

driven by hydrostatic and osmotic (oncotic) pressure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what is hydrostatic pressure

A

loss of water as you move down the capillary from arteriole to venule through clefts
big solutes remain in the capillary

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what is osmotic pressure

A

drawing water back in to the more concentrated plasma due to retention of large solutes in the capillary

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what is the pressure in the arteriole end

A

~40mmHg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what is the pressure in the venule end

A

~20mmHg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what are starlings forces

A

NOT THE SAME AS STARLING’S LAW (preload on the heart)
capillary hydrostatic pressure vs ISF hydrostatic pressure (determines movement of water out)
plasma osmotic pressure vs ISF osmotic pressure (determines movement of water in)
net filtration pressure
varies between capillary beds

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what amount of fluid is lost and regained in the capillary network each day

A

~20L lost and ~17L regained

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what happens to the remaining fluid that isn’t regained into the capillary network

A

drains into the lymph capillaries

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

describe the structure of lymph capillaries

A

same as blood capillaries except they are blind ended
valves prevent backflow of fluid
fluid drains into the low pressure heart of the systemic circulation (vena cava)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

define oedema

A

accumulation of XS fluid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

what are some causes of oedema

A

lymphatic obstruction e.g. due to filariasis, surgery
raised CVP e.g. due to ventricular failure
hypoproteinemia e.g. due to nephrosis, liver failure, malnutrition
increased capillary permeability e.g. inflammation, rheumatism

22
Q

how does filariasis cause oedema

A

parasitic worm

lives in lymph vessels and blocks them

23
Q

how does ventricular failure cause oedema

A

LV isnt pumpin out the blood that is coming into it
back up of pressure
increased loss of fluid from the veins

24
Q

how does rheumatoid arthritis lead to oedema

A

gaps between walls of capillaries and endothelial cells to allow WBC out
other contents of plasma are also drawn out so no build up of osmotic pressure
fluid accumulates

25
Q

how does malnourishment lead to oedema

A

lack of protein in diet
less plasma protein
no osmotic pressure developed
water is lost and isnt drawn back inn

26
Q

control of peripheral blood flow

A

Darcy’s law (flow = pressure difference/resistance) and Poiseuille’s law
varying the radius of vessels is used to control flow and redirect blood

27
Q

how is MAP calculated

A

flow = pressure difference/resistance
MAP - CVP = CO x TPR
MAP = CO x TPR

CVP is negligible as it is so small

28
Q

what is MAP

A

mean arterial pressure

~90-95 mmHg

29
Q

what does varying the radius of resistance vessels control

A

TPR and therefore regulates MAP

MAP is the driving force pushing blood through artieroles, continuous flow out of arterioles

arteriolar radius affects flow through individual vascular beds and MAP

30
Q

what happends is the resistance of a vascular bed is reduced

A

increased flow through that vascular bed

31
Q

if TPR is reduced, what effect does that have on MAP

A

reduced MAP
smaller driving force pushing blood through all arterioles
insufficient blood flow to the other regions

32
Q

what is used to keep the blood flow to each vascular bed sufficient and keep MAP in the right range

A

2 levels of control over the smooth muscle surrounding arterioles
intrinsic and extrinsic mechanisms

33
Q

what are intrinsic mechanisms

A

concerned with meeting the selfish needs of each individual tissue

34
Q

what are extrinsic mechanisms

A

tend to affect the whole body

concerned with ensuring that the TPR (and therefore MAP) of the whole body stays in the right range

35
Q

extrinsic control (neural)

A

sympathetic nerves - release noradrenaline, binds to alpha 1 receptors, arteriolar constriction, reduced flow through that body region, increased TPR

parasympathetic nerves - usually no effect

36
Q

what is the smooth muscle around vessels innervated by

A

heavily innervated by sympathetic post-ganglionic fibres

37
Q

extrinsic control (hormonal - adrenaline )

A

adrenaline - released from adrenal medulla when sympathetic nerves are activated, binds to alpha 1 receptors, arteriolar constriction, reduced flow through that tissue, increased TPR

in some tissues (skeletal and cardiac muscle) it also activates beta 2 receptors, arteriolar dilation (2y messengers coupled to receptors), increased flow through that tissue and reduced TPR
redirects blood to these muscles where it is needed

38
Q

extrinsic control (other hormonal controls)

A

angiotensin II - produced in response to low blood vol, arteriolar constriction, increased TPR
vasopressin (antidiuretic hormon) - released in response to low blood vol, arteriolar constriction, increased TPR
atrial natriuretic factor - released in response to high blood vol, arteriolar dilation, reduced TPR

39
Q

what are the 4 types of intrinsic control

A

active (metabolic) hyperaemia
pressure (flow) autoregulation
reactive hyperaemia
the injury response

40
Q

active (metabolic) hyperaemia

A

increased blood flow in response to increased metabolism
increased conc of metabolites
triggers the release of EDRF/NO by endothelium
causes arteriolar dilation
increased flow to wash out metabolites
an adaptation to match blood supply to the metabolic needs of that tissue

41
Q

what are paracrines

A

local signalling molecules

e.g. EDRF

42
Q

what does EDRF stand for

A

endothelium derived relaxing factor

43
Q

give 3 examples of metabolites

A

CO2
H+
K+

44
Q

pressure (flow) autoregulation

A

sudden event which leads to sudden decreased MAP, reduced flow and accumulation of metabolites

triggers release of EDRF/NO
arterioles dilate and flow is restored to normal
(or it could be myogenic - when smooth muscle is stretched it tends to contract which can contribute to the same effect)
an adaptation to ensure that a tissue maintains its blood supply despite changes in MAP

45
Q

reactive hyperaemia

A

occlusion of blood supply causes a subsequent increase in blood flow
an extreme version of pressure autoregulation

accumulation of metabolites when flow is cut off, local arteriolar dilation
when pressure is released there is a sudden flow of blood through dilated arterioles

46
Q

the injury response

A

aids delivery of blood born leucocytes etc to injured area

increased C fibre
substance P acts on mast cells
histamine released by mast cells
arteriolar dilation, increased blood flow and increased permeability

47
Q

special areas of circulation

A

coronary circulation
cerebral circulation
pulmonary circulation
renal circulation

48
Q

coronary circulation

A

majority of blood flow to coronary arteries is during diastole
blood supply is interrupted by systole
still has to cope with increased demand during exercise
shows excellent active hyperaemia
expresses many beta 2 receptors
these swamp any sympathetic arteriolar constriction

49
Q

cerebral circulation

A

always needs to be kept stable
shows excellent pressure autoregulation
if MAP decreases, the arterioles in the brain dilate enough to maintain enough blood flow to the brain

50
Q

pulmonary circulation

A

reduced oxygen causes arteriolar constriction (the opposite response to most tissues)
ensures that the blood is directed to the best ventilated parts of the lung
prevents V/Q mismatch

51
Q

renal circulation

A

main function is filtration which depends on pressure
changes in MAP would have big effects on blood volume
shows excellent pressure autoregulation
if MAP falls, arterioles dilate and vice versa to maintain filtration at a constant level

cardiovascular system year 1 (13 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions