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CVS > L09: Special Circulations > Flashcards

L09: Special Circulations Flashcards

1
Q

Where does coronary arteries lie

A

On the pericardium

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2
Q

Which atrium does the coronary veins empty into

A

Right atrium

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3
Q

Which organ has the highest a-vo2 difference

A

Heart

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4
Q

Which organs have the smallest a-vo2 difference

A

Kidney

Skin

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5
Q

Where does the coronary artery originate from

A

Aorta (just after the aortic valve)

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6
Q

Are cardiac muscles highly or low perfused

A

Highly perfused

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7
Q

What adaptation of the cardiac myocytes allow it to have a reduced diffusion distance

A

High capillary density

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8
Q

In the coronary circulation what does haemoglobin hand the oxygen to

A

Myoglobulin

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9
Q

What is the affinity of oxygen to myoglobulin compared to haemoglobin

A

Higher affinity for oxygen

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10
Q

What does myglobulin do to the speed of oxygen transport inside the myocytes

A

Increase the speed of oxygen transport

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11
Q

What mechanism controls the blood flow in coronary circulation

A

Auto regulation via a myogenic response

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12
Q

What other things control the blood flow

A

Sympathetic innervation
Local factors
Endothelial factors

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13
Q

What are local factors

A

Factors from metabolism

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14
Q

List the substances from metabolism

A

Carbon dioxide
Potassium
Hydrogen ions
Adenosine

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15
Q

Which endothelial factors released from blood vessel result in vasodilation

A

Prostaglandins
Nitric oxide
Endothelial derives hyper-polarisation factors

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16
Q

What happens to blood flow in the coronary arteries when they are blocked

A

Blood flow decreases

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17
Q

What happens to the endothelial factors if the blood vessel walls are damaged due to the blockage

A

Decrease

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18
Q

What does reduced blood flow to the coronary circulation result in

A

Angina (chest pain).

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19
Q

Which type of angina is the most serious

A

Unstable angina (thrombus)

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20
Q

What vessels take blood to the brain

A

2 vertebral arteries

2 carotid arteries

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21
Q

What is the circle of Willis

A

The circle of blood vessel formed when vertebral arteries join to carotid arteries

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22
Q

What is the density of the capillaries like in the grey matter

A

High density

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23
Q

What does the high density of capillaries allow in the grey matter

A

Short diffusion distance for exchange

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24
Q

What type of junction does the blood brain barrier have

A

Tight junctions

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25
Q

What controls the blood flow to the brain

A

Auto regulation via myogenic response

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26
Q

What happens to the blood flow to other organs if the brain does not have enough blood flow

A

Other organs undergo peripheral vasoconstriction to main ABP and cerebral flow

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27
Q

What is hypercapnia

A

High carbon dioxide

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28
Q

What is hypocapnia

A

Vasoconstriction

29
Q

What does hypercapnia do to the blood flow in the cerebral vessel

A

Increase it by vasodilation

30
Q

What does hypocapnia do to the blood flow in the cerebral vessels

A

Decrease it via vasoconstriction

31
Q

Are cerebral vessels responsive to levels of arterial oxygen as much as carbon dioxide

A

No they are less responsive

32
Q

When does cerebral blood flow react to oxygen levels

A

When there is severe hypoxia

33
Q

What substances does functional hyperaemia result in

A

Potassium
Adenosine
Carbon dioxide
Hydrogen ions

34
Q

What causes a raised intracranial pressure

A

Bleeding
Cerebral oedema
Tumour

35
Q

What happens to cerebral blood flow in postural syncope when you stand up

A

Cerebral blood flow decreases

36
Q

What are the 2 main functions of the cutaneous circulation

A

Provide spine with modest metabolic requirements

Regulate body temperature

37
Q

What is the network of cutaneous circulation like

A

Arteries give rise to arteriole that penetrate dermis to give capillaries
Blood flows into the venous plexus
Blood from arteries also give blood to venous plexus

38
Q

How does he venous receive blood from the arteries

A

By arteriovenous anastomoses

39
Q

What is the skin vessel mostly under the influence of

A

Sympathetic NS

40
Q

What happens to the skin vessel when there is an increased temperature

A

1) arterioles dilate due to withdrawal of the SNS
2) AVA also dilates and increases blood flow straight into the venous plexus
3) increase in blood to the venous plexus provide a large area of heat exchange between the blood and skin and environment

41
Q

What is the hypothalamic stimulation of the sympathetic fibres innervating the sweat glands

A

1) sweat glands receive innervation by the sympathetic fibres
2) sweat glands release bradykinin which causes the production of NO
3) this cause vasodilation to the cutaneous vessels and therefore heat loss

42
Q

What happens to the TPR when there is an increase in temperature and vasodilation occurs as a result

A

TPR decreases

43
Q

What happens to the ABP when TPR decreases

A

ABP decreases

44
Q

When the ABP falls which reflex detects the change in pressure

A

The baroreceptor reflex

45
Q

How does the baroreceptor reflex affect the heart

A
  • decreases vagal activity (PNS) and increases SNS activity to the heart to increase HR
46
Q

As a result in an increase HR what happens to the CO

A

Increase

47
Q

If the CO output increases what happens to the ABP

A

Increases to normal

48
Q

Therefore as a result of increased temperature how does it affect the heart overall

A

Tachycardia due to an increased heart rate

49
Q

Describe what happens when there is a drop in temperature

A

1) SNS activity to the arterioles increase
2) vasoconstriction occurs
3) in addition AVA constricts so there is less blood flow into the venous plexus
4) this minimises heat loss by keeping blood away from the surface

50
Q

In a decreased temperature when skin vessels vasoconstrict where is blood diverted to

A

Deep vessels that lye beneath insulating fat (interior vessels)

51
Q

What happens to the cutaneous circulation when there is a prolonged exposure to cold

A

Cold induced vasoconstriction changes to a paradoxical cold vasodilation

52
Q

What does a paradoxical cold vasodilation result in the skin

A

Red appearance

53
Q

Why do we get a paradoxical cold vasodilation

A

Paralyses of NA transmission in response to cold

54
Q

How do we transfer heat to the blood returning from the cold periphery

A

Via a countercurrent exchange

55
Q

What is a Raynaud’s disease

A

When the skin vessels are overactive due to extreme vasoconstriction when exposed to cold

56
Q

What does the pressure have to be like for blood to flow in a VESSEL

A
  • flow depends on perfusion pressure
  • artrial pressure is greater than venous pressure and theses 2 pressures have to be greater than the pressure outside (pressure in the ventricles)
57
Q

What does the pressure inside represent

A

Pressure in aorta

58
Q

What is the pressure outside

A

Pressure in the ventricles

59
Q

What happens to the flow in the left coronary artery when there is systole of the ventricles

A

Decrease

60
Q

Why does the coronary artery flow decrease in systole

A

The pressure outside i.e the ventricles is greater than the pressure in the aorta i.e the coronary artery (pressure inside the VESSELS)

61
Q

What happens when the pressure outside the vessels i.e the ventricles exceed the pressure inside the VESSELS

A

Extravascular compression in the left ventricular wall

62
Q

What happens to the blood flow during extra vascular compression the left ventricular wall

A

Coronary blood flow reverse as the myocytes squeeze the coronary vessels

63
Q

What happens to the blood flow in the RIGHT coronary vessels when there is right ventricular contraction

A

Blood flow will increase

64
Q

Why does the blood flow increase in systole in the RIGHT coronary vessel

A

The pressure inside the vessel i.e the aorta and therefore the coronary vessel increases greater than the pressure outside the vessel i.e the ventricular pressure

65
Q

By how much does the aortic pressure increase in systole

A

40 mmhg

66
Q

How much pressure increase is there in the right ventricular pressure in systole

A

25 mmHG

67
Q

Why does the right ventricular pressure not increase as much as the left ventricular pressure

A

The right ventricular pressure doesn’t need a lot of pressure to overcome the pulmonary resistance whereas the left ventricular pressure needs a bigger pressure to overcome the systemic resistance

68
Q

At what phase is the left coronary flow the highest

A

During diastole

69
Q

At what phase is the right coronary artery the highest

A

During systole

CVS (19 decks)

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