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PHSL 232 > L11 > Flashcards

L11 Flashcards

1
Q

what is the role of the vascular bed (capillary network) in each organ

A

perfuses the organ and delivers O2 and removes CO2

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2
Q

what is blood flow regulated by

A

myogenic, neural and metabolic control

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3
Q

is regulation of blood flow uniform in all of the organs. why?

A

no because some vascular beds are specialised

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4
Q

what is special about cardiac muscle in terms of it specialised regulation of blood flow

A

the muscle is completely dependent on aerobic metabolism (compeered to skeltal which can do both)

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5
Q

what is special about the pulmonary blood flow

A

it is the only organ that receives 100% of the CO as it is the site of gas exchange

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6
Q

describe the locations of the coronary vessels

A

large coronary arteries are on the epicardial surface

smaller vessels penetrate into the myocardium

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7
Q

how much of the CO do the coronary arteries receive

A

5%

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8
Q

where do the coronary arteries arise from

A

just outside of the aortic root by the the SL valve

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9
Q

what helps blood flow into the coronary arteries

A

recoil

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10
Q

what does the right main coronary artery supply

A

the right main coronary artery supplies blood to the RA, RV and inferior posterior region of the LV

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11
Q

what does the left main coronary artery split into

A

the circumflex and left anterior descending arteries

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12
Q

what does the circumflex artery supply

A

the La and the posterior LV

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13
Q

what does the left anterior descending artery supply

A

the anterior side of the left ventricle

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14
Q

why does the heart have a dense cappilary network

A

it ensures that each cardiac muscle cell is closely associated with several capillaries. this is important because cardiac muscle cells can only use aerobic respiration therefore they need to have a good supply of O2 and fast removal of waste

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15
Q

where do all the cardiac veins empty back into

A

the coronary sinus which empties into the right atrium

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16
Q

when is the myocardium perfused

A

during diastole

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17
Q

what happens to cardiac circulation during systole

A

myocardium contraction causes the vessels to become compressed decreasing the radius therefore increasing resistance and decreasing the floow

the opposite happens during diastole

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18
Q

what % od perfusion to the hart happens during diastole

A

75%

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19
Q

what makes puffusion different in the heart compered to other parts i the body

A

it is pulsatile

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20
Q

what is the difference between the left and the right sides of the heart in terms of blood flow and puffsion

A

the right does not experience the pulsatile effects as much as the left side

this is because the right side is not as strong as the left therefore it doesn’t contract as much

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21
Q

what % of O2 does the heart extract from the blood

A

65-75%

it is always working at maximum which means that increased O2 demand in the heart means that it has a limited ability to extract more O2 from the blood

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22
Q

how does the heart increase its O2 levels when it has higher metabolic demands eg when exercising

A

the heart has the ability to increase its O2 capacity by 5x

it does this through its vasodilator reserve capacity

increased O2 demand = increased flow to the heart

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23
Q

what are the extrinsic regulator of coronary blood flow

A

the sympathetic nervous system

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24
Q

how does the sympathetic NS have extrinsic control over coronary blood flow

A

it releases noradrenaline which binds to alpha adrenergic receptors OR beta adrenergic receptors

25
what happens when noradrenaline binds to the alpha adrenergic receptors
it causes vasoconstriction which leads to increased resistance
26
what happens when noradrenaline binds to the beta adrenergic receptors
it leads to increased HR and SV
27
why is extrinsic regulation of coronary blood flow not suitable
because it only has a transient effect as b increases work but a decreases supply therefore this is overcome by metabolic autoregulation
28
what is the primary regulator of coronary blood flow
metabolic autoregulation aka active hyperemia
29
what is active hyperemia
metabolic autoregulation this is when you have increased metabolic activity which leads to less O2 and more waste products. adenosine and hypoxia leads to vasodilation which increases blood flow to the organ
30
what are some vasodilator messengers that are able to regulate coronary blood flow
increased metabolism (increased AMP) leads to the production of adenosine endothelium also produce NO both of these cause vasodilation these happen in hypoxia (low O2)
31
how many people in NZ dies of cardiovascular disease
1 in 3 one every 90 min
32
what is atherolosclerosis
it is the underlying cause of heart disease and is the development of lesions (plaques) in arterial wall of larger arteries
33
what are some common sites of atherosclerosis
``` Aortic sinus Aortic arch Brachiocephalic Carotid arteries Large epicardial arteries (LAD, Right coronary, circumflex) ```
34
when does atherosclerosis start to cause symptoms of heart disease
when 60 - 70% of the lumen is black which means that distal to where the blockage is wont receive O2
35
what are some risk factors of heart disease
high cholesterol, smoking and age
36
what is angina
Angina is a type of chest pain caused by reduced blood flow to the heart
37
what is a myocardial infarction
it is a heart attack occurs when blood flow to the heart muscle is abruptly cut off
38
what is stenosis
90% blockage
39
how does atherosclearosis affect the production of nitric oxide
it changes supply and demand which impacts NO production because NO is a mechanism for increasing flow as metabolic autoregulation. less metabolism = less NO
40
how does coronary atherosclerosis effect the myocardial supply and demand ratio
it means that increased demand does not = increased supply as more blood cant get there therefore coronary disease causes a decrease in maximal coronary blood flow
41
what happens when NO production decreases
increased resistance --> decreases flow decreased vasodilatory reserve capacity --> exercise induced angina (chest pain)
42
why is the pulmonary circuit highly branches
You can get up to 20 different branches in the pulmonary circulation You need a haigh surface area as this is where diffusion takes place In the lungs it is a range of parallel circuits
43
describe the characteristics of the pulmonary circulation
it is a high flow, low pressure, low resistance, high compliance system
44
compare the pressure between the pulmonary and systemic circuits
pulmonary = 25/10mmHg systemic = 120/80mmHg
45
how many more x lower is the resistance in the pulmonary circuit compeered to the systemic circuit
10 to 15x lower this is because of shorter vessels (therefore lower resistance). the veins and arteries also have a large radius
46
what happens in the lungs when CO increases
the lungs receive 100% of the cardiac output therefore they need to have high compliance for when the CO increases as they need to be able to keep the pressure the same for perfusion
47
what is different about starling's forces in the pulmonary circuit
because of the low pressure in the pulmonary circuit water is more likely to go back into the circulation then it is to go out. this is good because you don't want water in the lungs as it would affect gas diffusion
48
what is postures effect on the lungs
when you are standing up there is a difference in pressure between the upper and the lower lung
49
what is the difference between hypER and hypOfussion
hypO is in the upper lung and hypER is in the lower lung
50
what is postors effect on the upper lung
a decrease in hydrostatic pressure and vessels partially collapse. this causes an increase in resistance and a decrease in blood flow hypofussion
51
what is postures effect on the lower lung
increase in hydrostatic pressure therefore vessels become distended. this decreases resistance and increases blood flow hyperfusion
52
what is the importance of hyper and hypofusion
With excursive you have a increase in CO and the hypoperfusion gives us the capacity to be able to dilate and spread the blood flow around all of the lung it allows for extra space for the extra blood to go
53
what does a reduction in pulmonary O2 lead to
constriction If there is no fresh air going into the avioli then the blood will be redirected. Eg if there is no O2 at a specific alvioli then the arteries supplying at avoli will constrict and the blood will be redirected Therefore you are matching ventilation and perfusion and by doing this we are optimising the gas exchange in the P circuit
54
what are the 2 ways on intrinsic control of pulmonary blood flow
NO and endothelin 1 from the endothelium NO causes the smooth muscle to relax --> vasodilation --> decreased resistance and increases flow ET1 contracts smooth muscles therefore it is the opposite
55
what does imbalance of the intrinsic control mechanisms in the pulmonary circuit lead to
pulmonary hypertension
56
what is the extrinsic control over the P circuit
the SNS alpha adrenoreceptors are mainly found in the large conduit vessels (right and left pulmonary artery) whereas beta adrenoreceptors are in the smaller resistance vessels a causes vasoconstriction b cause vasodilation normally these will balance eachother out
57
why do we have extrinsic controls if they cancel each other out
We have this because we need to be able to adapt to changes Eg when you go up altitude there is less O2 therefore it will cause vasoconstriction in the alveoli because none of them will have good O2 levels. This causes the SNS to kick in and overcome this to cause vasodilation to overrule generalised hypoxia
58
In the pulmonary circulation, hypoxia will cause the vasculature to: A: Dilate to increase flow to under ventilated regions B: Constrict to redirect blood flow to well ventilated regions C: Dilate to remove excess waste products D: Constrict to reduce flow to increase the time available for gas exchange
B
59
Coronary blood flow increases during diastole BECAUSE the elastic recoil of the aorta produces the pressure required to provide flow in the coronary system during diastole
both statements are true and causal

PHSL 232 (30 decks)

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