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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
Q

what happens when noradrenaline binds to the alpha adrenergic receptors

A

it causes vasoconstriction which leads to increased resistance

26
Q

what happens when noradrenaline binds to the beta adrenergic receptors

A

it leads to increased HR and SV

27
Q

why is extrinsic regulation of coronary blood flow not suitable

A

because it only has a transient effect as b increases work but a decreases supply

therefore this is overcome by metabolic autoregulation

28
Q

what is the primary regulator of coronary blood flow

A

metabolic autoregulation

aka active hyperemia

29
Q

what is active hyperemia

A

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
Q

what are some vasodilator messengers that are able to regulate coronary blood flow

A

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
Q

how many people in NZ dies of cardiovascular disease

A

1 in 3

one every 90 min

32
Q

what is atherolosclerosis

A

it is the underlying cause of heart disease and is the development of lesions (plaques) in arterial wall of larger arteries

33
Q

what are some common sites of atherosclerosis

A 
Aortic sinus
Aortic arch
Brachiocephalic
Carotid arteries
Large epicardial arteries
(LAD, Right coronary, circumflex)
34
Q

when does atherosclerosis start to cause symptoms of heart disease

A

when 60 - 70% of the lumen is black which means that distal to where the blockage is wont receive O2

35
Q

what are some risk factors of heart disease

A

high cholesterol, smoking and age

36
Q

what is angina

A

Angina is a type of chest pain caused by reduced blood flow to the heart

37
Q

what is a myocardial infarction

A

it is a heart attack

occurs when blood flow to the heart muscle is abruptly cut off

38
Q

what is stenosis

A

90% blockage

39
Q

how does atherosclearosis affect the production of nitric oxide

A

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
Q

how does coronary atherosclerosis effect the myocardial supply and demand ratio

A

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
Q

what happens when NO production decreases

A

increased resistance –> decreases flow decreased vasodilatory reserve capacity –> exercise induced angina (chest pain)

42
Q

why is the pulmonary circuit highly branches

A

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
Q

describe the characteristics of the pulmonary circulation

A

it is a high flow, low pressure, low resistance, high compliance system

44
Q

compare the pressure between the pulmonary and systemic circuits

A

pulmonary = 25/10mmHg

systemic = 120/80mmHg

45
Q

how many more x lower is the resistance in the pulmonary circuit compeered to the systemic circuit

A

10 to 15x lower

this is because of shorter vessels (therefore lower resistance). the veins and arteries also have a large radius

46
Q

what happens in the lungs when CO increases

A

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
Q

what is different about starling’s forces in the pulmonary circuit

A

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
Q

what is postures effect on the lungs

A

when you are standing up there is a difference in pressure between the upper and the lower lung

49
Q

what is the difference between hypER and hypOfussion

A

hypO is in the upper lung and hypER is in the lower lung

50
Q

what is postors effect on the upper lung

A

a decrease in hydrostatic pressure and vessels partially collapse. this causes an increase in resistance and a decrease in blood flow

hypofussion

51
Q

what is postures effect on the lower lung

A

increase in hydrostatic pressure therefore vessels become distended. this decreases resistance and increases blood flow

hyperfusion

52
Q

what is the importance of hyper and hypofusion

A

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
Q

what does a reduction in pulmonary O2 lead to

A

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
Q

what are the 2 ways on intrinsic control of pulmonary blood flow

A

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
Q

what does imbalance of the intrinsic control mechanisms in the pulmonary circuit lead to

A

pulmonary hypertension

56
Q

what is the extrinsic control over the P circuit

A

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
Q

why do we have extrinsic controls if they cancel each other out

A

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
Q

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

A

B

59
Q

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

A

both statements are true and causal

PHSL 232 (30 decks)

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