Cardiovascular L5/6: Blood vessel function and determinants of flow; Blood vessel properties - arteries and arterioles Flashcards
(88 cards)
1
Q
What is the main function of blood vessels? (Name 5 functions)
A
‘Vascular highways’ that transport blood around the body to meet demands:
- Oxygen delivery
- Nutrient delivery (GIT –> bloodstream)
- Waste removal (CO2 after aerobic metabolism)
- Chemical messenger delivery (e.g. hormones- produced in another organ- travels via bloodstream)
- Maintain body temperature (cold: periphery constrict; hot: periphery dilate)
2
Q
Arteries transport blood ____ (into/out of) the heart
A
out of
3
Q
Arterioles regulate the flow of blood _____ (into/out of) tissues
A
into
4
Q
Capillaries _______ substances in blood (nutrients, gases, hormones) with tissues
A
exchange
5
Q
Venules carry away the waste _____ tissues. The venule starts to become a _____.
A
from; vein
6
Q
Veins transport blood ______ the heart
A
into
7
Q
What is the pulmonary circulation? List the 3 steps
A
- Oxygenated blood from left side of heart goes to systemic arterial circulation
- supplies various tissues
- deoxygenated blood returns via systemic veins to right side of heart
8
Q
What is the systemic circulation?
A
- Deoxygenated blood from right side of heart goes to pulmonary arterial circulation
- gas exchange in lungs
- oxygenated blood returns via pulmonary veins to le] side of heart
9
Q
Is the blood oxygenated or deoxygenated in arteries in the systemic circulation?
A
Oxygenated
10
Q
Is the blood oxygenated or deoxygenated in arteries in the pulmonary circulation?
A
Deoxygenated
11
Q
Is the blood oxygenated or deoxygenated in veins in the systemic circulation?
A
Deoxygenated
12
Q
Is the blood oxygenated or deoxygenated in veins in the pulmonary circulation?
A
Oxygenated
13
Q
How is blood distributed around the body? 3 characteristics.
A
- Parallel arrangement of vessels from the aorta ensures fresh blood to all organs
- More blood goes to organs that are responsible for ‘reconditioning’ blood
- Other organs receive just enough blood to meet needs & therefore ‘less tolerant’ of reductions in blood flow – e.g. the brain
14
Q
_______ arrangement of vessels from the aorta ensures fresh blood to all organs
A
Parallel
15
Q
More blood goes to organs that are responsible for _______ the blood. Give examples of 2 organs.
A
‘reconditioning’
Eg.
- kidneys-waste control (20%)
- digestive system (20%)- able to go lomger without blood because there is less.
16
Q
Other organs receive _______ blood to meet needs & therefore ‘_____ (more/less) tolerant’ of reductions in blood flow. Give an example of an organ.
A
just enough; less
- Brain
- Only 4 mins without oxygen before irreversible damage
17
Q
How much (L) is the average cardiac output?
A
5L/min
18
Q
Blood flow to each organ can be changed independently. True or false.
A
True
19
Q
What is flow rate?
A
volume per unit of time
20
Q
Flow rate is ______ (directly proportional/inversely proportional) to pressure gradient.
A
directly proportional
F ∝ ΔP/R
F = flow rate
ΔP = pressure gradient
R =resistance
21
Q
Flow rate is ______ (directly proportional/inversely proportional) to vessel resistance.
A
inversely proportional
F ∝ ΔP/R
F = flow rate
ΔP = pressure gradient
R =resistance
22
Q
What is a pressure gradient (ΔP)?
A
Difference between the start & end of a vessel
23
Q
What are 3 characteristics of a pressure gradient (ΔP)?
A
- Difference between the start & end of a vessel
- Blood flows down a pressure gradient, from high to low
- Contraction of heart is the main driving force for blood flow
24
Q
Blood flows down a pressure gradient, from ___ (high/low) to _____ (high/low).
A
high; low
25
\_\_\_\_\_\_\_\_ of heart is the main driving force for blood flow
Contraction
\* The aorta has very high pressure (main driving force of blood)
26
How is blood flow affected by pressure gradient (ΔP)?
* The greater the ΔP, the greater the flow
* Pressure is lower at the end of a vessel because of frictional loss (resistance) along vessel length
27
How does the pressure gradient change from the start to the end?
Start --\> high pressure
Further down --\> low pressure
Even further down --\> meets arterioles (due to decreased radius)
28
Flow is determined by the pressure difference between the ____ and the ____ of a vessel - not the _____ pressures!
start; end; absolute
29
The greater the ΔP, the ______ (greater/lesser) the flow
greater
30
Pressure is lower at the end of a vessel because of ____________ along vessel length
frictional loss (resistance)
31
Is blood flow the same between these vessels?
Yes, doesn't matter what the absolute, start and end pressures are.
ΔP= has an effect
32
How is blood flow affected by R?
* The greater the R, the lower the flow
* Resistance is directly proportional to viscosity of blood & length of vessel, &inversely proportional to radius of vessel which has the greatest impact
R ∝ ηL / r4
where η = blood viscosity
L = vessel length
r = vessel radius
(L and r = surface area)
33
What is resistance (R)?
Opposition to blood flow caused by friction between blood flow &vascular walls
34
The greater the R, the ______ (higher/lower) the flow
lower
35
Resistance is _________ (directly proportional/inversely proportional) to viscosity of blood & length of vessel. However, resistance is _________ (directly proportional/inversely proportional) to radius of vessel which has the greatest impact
directly proportional; inversely proportional
36
What is Poiseuille's Equation in terms of blood viscosity (n)?
the thicker a liquid, the greater the viscosity
**Increased viscosity = increased R =decreaseed F**
37
What is Poiseuille's Equation in terms of surface area (L/r4)?
the longer a vessel and smaller a radius, the greater the surface contact with blood
**decreased r (increased surface area) = increased R = decreased F**
38
Increased viscosity = ______ R = ______ F
increased; decreased
39
Decreased r (increased surface area) = _____ R = ______ F
increased; decreased
40
What are the 3 factors that affect resistance and in turn affects blood flow?
1. Viscosity of blood
2. Length of vessel
3. Radius of vessel
41
The radius (r) has a major effect on R & ultimately flow. True or false.
True
A slight change in r causes a considerable change,
i.e. R ∝ 1/r4
42
What happens to resistance (when there is an increase in r)?
ADD
43
What happens to blood flow (when there is an increased in r)
ADD
44
Upon arterial stenosis (thus increased resistance), how does ΔP increase to maintain adequate flow? Hint: what is the main driving force for flow? F = ΔP / R
Heart will work harder (contraction) = compensate = increased pressure
How?
= increased HR
= increased strength of contraction
45
Arteries are \_\_\_\_\_\_. (main function) How does this work?
pressure reservoirs 1/3 of blood is transported from arteries to arterioles. The excess (2/3) of blood is held in arteries.
**Not all of the blood that enters arteries flows into the smaller, high resistance arterioles**
46
\_\_\_\_\_\_ allows arteries to expand like a balloon & temporarily hold excess blood
Elastin
47
What is the function of elastin in arteries?
allows arteries to expand like a balloon and temporarily hold excess blood
48
When the heart is in diastole, stretched arterial walls _____ & exert pressure on the blood, ensuring _______ even when the heart is relaxed & not pumping
recoil; continued flow
49
How do arteries act as a pressure reservoir? What is the most important material?
* Elastin fibers allow arteries to expand during systole... (stores energy)
* Elastin fibres allow arteries to passively recoil during diastole (this is less than a heart beat)
50
Why does blood flow not stop in arteries?
Hold blood and pressure and is realised during diastole
51
What are 2 things that blood pressure depends on?
1. Volume of blood
2. Compliance of vessel
52
What is blood pressure?
the force exerted by blood against a vessel wall
53
Blood pressure fluctuates during the cardiac cycle. True or false.
True
54
During ventricular contraction, the volume of blood that enters the arteries (stroke volume) is about one third ____ (greater/lesser) than what leaves & enters the arterioles
greater
55
During ventricular relaxation, blood ____ (does/does not) enter arteries although blood flow from arteries into arterioles contnues due to the \_\_\_\_\_\_\_\_\_.
does not; elastic recoil
56
What is systolic pressure?
the max pressure in arteries when blood is pumped into them
57
What is diastolic pressure?
is the min pressure in arteries when there is no heart contraction & blood continues to flow into arterioles
58
What is pulse pressure?
the difference between systolic & diastolic pressures. It is this pressure difference we can feel when taking our pulse
59
What is mean arterial pressure (MAP)?
the average pressure during each cardiac cycle. This is the pressure that the body monitors & regulates
60
What is the average systolic pressure?
120mmHg
61
What is the average diastolic pressure?
80mmHg
62
What is the average pulse pressure?
40mmHg
63
What is the equation for MAP? What is the mean arterial pressure (MAP)?
**MAP = diastolic pressure + 1/3 (systolic – diastolic)**
MAP = 93mmHg
64
Why is MAP = 93mmHg? Why isn't MAP simply half way between systolic and diastolic pressure i.e. 100mmHg?
The heart is is diastole for longer than systole. Since it is specifically 2/3 longer at rest, the MAP is closer to diastole.
65
Why does the pressure not drop in arteries?
No resistance to flow = no pressure drop
66
Why does the pressure start to drop in arterioles?
There is high and variable resistance = decreased pressure
67
Why does arterial pressure never drop to zero, unlike ventricular pressure?
next contraction fills arteries again, before all the blood has flowed out
68
Why is there a decrease in pressure in venules and veins until 3 mmHg? Why not until 0mmHg?
Higher than heart (at 0mmHg) so that blood can continue to flow into heart (from high pressure to low pressure)
69
What is the main function of arterioles?
regulate blood flow to tissues
70
What are 3 features of arterioles?
1. Branches of an artery within an organ
2. High resistance vessels due to small radius
3. Profound fall in mean pressure as blood flows through these small vessels (93 --\> 37 mmHg)
* This pressure difference helps to maintain flow of blood downstream Arterioles: regulate blood flow
71
Arterioles are branches of an ____ within an organ.
artery
72
Arterioles have ____ (high/low) resistance due to the ___ (large/small) radius.
high; small
73
There _____ is/isn't a profound fall in mean pressure as blood flows (in regards to arterioles)? Why?
is
This pressure difference helps to maintain flow of blood downstream
74
MAP for all organs is \_\_\_\_\_\_, and the amount of blood delivered to each organ ________ (& can be temporally adjusted)
identical; varies
75
What are 2 reasons why there is a difference between the amount of blood being delivered to each organ?
1. Organ vascularisaton (capillary- how much SA)
2. Arteriolar resistance
76
R can be changed independently in organs –why? List 2 reasons
1. distribute blood variably according to needs at any point in time
2. help regulate arterial blood pressure
77
R can be changed independently in organs –How? List 2 ways.
1. Vascular tone
2. Vasoconstriction/dilation
78
What is vascular tone? List 2 features
1. partial constriction for baseline resistance due to myogenic activity (intracellular Ca2+)
2. continuous sympathetic innervation
79
What is vasoconstriction/dilation? List 2 features.
1. sensitive to various factors
2. highly innervated by sympathetic nerves
80
The vascular smooth muscle can undergo changes in force without _______ (unlike skeletal & cardiac). What does this mean? Graded or non-graded?
action potentials; graded
81
What are 2 intrinsic (right at site/local) factors that regulate blood pressure?
1. Chemical
2. Physical
82
What are 2 extrinsic (general) factors that regulate blood pressure?
1. Neural (sympathetic NS)
2. Hormonal (whole bloodstream)
83
How does a chemical intrinsic factor regulate blood pressure? List 2 features.
1. Metabolic changes (exercise): increase O2, CO2, lactic acid, K+, osmolarity, adenosine (increases HR), vasocative paracrines from endothelial cells
2. Histamine release: not released in response to local changes, important in pathology
84
How does a physical intrinsic factor regulate blood pressure? List 3 features
1. Vessel stretch/myogenic: opening of mechanically-gated cation channels causes Ca2+ influx & contraction
2. Shear stress: friction of blood on inner surface of vessels creates a force, releasing NO (vasodilate)
3. Hot/cold: heat causes localised vasodilation (exercise- to cool down) &cold causes vasoconstric4on
85
How does a neural extrinsic factor regulate blood pressure? List 2 features.
1. Innervates smooth muscle everywhere in the systemic circulation for vasoconstriction, except the brain – Noradrenaline binds to α1-adrenergic receptors on arteriolar smooth muscle (none on cerebral arterioles)
2. Contributes to ongoing vascular tone &generalised vasoconstriction increases TPR & therefore MAP
86
How does a hormonal extrinsic factor regulate blood pressure? List 2 features.
1. Noradrenaline &adrenalin generally reinforce the sympathetic nervous system
2. Anti-diuretic hormone & angiotensin II also important in fluid balance &blood volume
87
Of all systemic peripheral vessels, ______ resistance has the greatest impact on TPR. Why?
arteriolar
primary resistance vessels
88
What is TPR?
Total peripheral resistance- combination of all the resistance
