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CVS > Special Circulations > Flashcards

Special Circulations Flashcards

1
Q

What are the 2 circulations to the lungs?

A

Bronchial circulation

Pulmonary circulation

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2
Q

What is Bronchial circulation?

A

Part of systemic circulation which supplies Oxygen to the parts of the lungs NOT CLOSE to thee alveoli

It meets the metabolic requirements of the lungs

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3
Q

What is the pulmonary circulation to the lungs?

A

Blood supplied to the alveoli for gas exchange

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4
Q

What is the normal cardiac output for the typical 70kg male at rest?

A

5 L/min

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5
Q

What physiological situation does Cardiac Output increase with?

A

Exercise

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6
Q

What chamber of the heart is the pressure of the pulmonary artery equal to during SYSTOLE?

A

Right Ventricle

(Pulmonary artery pressure = Right ventricular pressure in diastole)

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7
Q

Is the pressure of the pulmonary artery less than, equal to or greater than the right ventricle in DIASTOLE?

Why?

A

Pulmonary artery pressure > RV pressure

Elastic recoil of artery makes it greater

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8
Q

What is the relative pressure of the right atrium compared to the right atrium during DIASTOLE?

A

Pressures equal

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9
Q

What chamber of the heart is the pressure of the aorta equal to during SYSTOLE?

A

Left ventricle

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10
Q

Is the pressure of the aorta less than, equal to or greater than the Left ventricle in DIASTOLE?

Why?

A

Aorta pressure greater than LV in diastole

Elastic recoil or aorta makes it a greater pressure

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11
Q

In terms of pressures, how are the atrial and ventricular pressures related in DIASTOLE?

A

Pressure of ATRIA = Pressure of Ventricles

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12
Q

What relative pressure and resistance does the pulmonary circulation/right side of the heart work at?

A

Low pressure
Low resistance

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13
Q

What relative pressure and resistance does the systemic circulation/left side of the heart work at?

A

High pressure
Higher resistance

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14
Q

What contributes to the low pressure of the pulmonary circulation?

A

Low Mean Arterial Pressure
Low Mean Capillary Pressure
Low Mean Venous Pressure

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15
Q

What contributes to the low resistance of the pulmonary circulation?

A

Short + wide vessels
Lots of capillaries (lots of parallel elements)
Arterioles have relatively little smooth muscle

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16
Q

What contributes to the High pressure of systemic circulation?

A

High Mean Arterial Pressure
HighMean Capillary Pressure
High Mean Venous Pressure

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17
Q

What contributes to the High resistance of systemic circulation?

A

Long + Narrow vessels
Variable blood flow to capillaries
Arterioles have relatively thick smooth muscle walls

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18
Q

What are the 2 adaptations to promote efficient gas exchange at the lungs?

A

High capillary density in Alveolar wall(Large SA)

Short diffusion distance

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19
Q

What needs to match the rate of ventilation of alveoli for efficient gas exchange?

A

Ventilation of alveoli = Perfusion of alveoli

Ventilation must match perfusion

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20
Q

What is the optimal perfusion ratio (V/Q ratio)?

A

V/Q = 0.8

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21
Q

How may mucus build up affect Perfusion ratio (V/Q ratio)?

A

Mucus prevents ventilation so means any perfused blood is not oxygenated

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22
Q

How is blood diverted away from alveoli that are not well ventilated to maintain an optimal V/Q ratio?

A

Hypoxic pulmonary vasoconstriction

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23
Q

What is hypoxic pulmonary vasoconstriction?

A

When the pulmonary blood vessels constrict in a response to hypoxia

Ensures that perfusion matches ventilation so that poorly ventilated alveoli get less perfused (maximising gas exchange)

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24
Q

How is hypoxic pulmonary vasoconstriction different to the response of hypoxia in the systemic circulation?

A

Response is opposite

In systemic vasodilation happens to maximise blood flow to area

In pulmonary vasoconstriction happens to keep blood away from areas that it wont get oxygenated

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25
Q

What negative effects can happen as a result of Chronic hypoxic vasoconstriction?

A

Chronic increase in vascular resistance causing Chronic Pulmonary Hypertension
High AFTERLOAD on RV, leads to RV Hypertrophy and eventually RV HEART FAILURE (this is called cor pulmonale)

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26
Q

How does gravity effect the lower pressure blood vessels of the pulmonary circulation?

A

Strongly

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27
Q

How does pressure affect the status of the vessels in the lungs during diastole at the Apex of the lungs, level of the heart and base of the lungs?

A

Apex vessels - Collapse during diastole, open in systole

Level of Heart vessels - Continuously open

Base of lung vessels - Vessels constantly distended/swollen

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28
Q

How does hydrostatic pressure in blood vessels change as you go down the body?

A

Increased pressure

More fluid above

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29
Q

What happens to pulmonary blood flow in exercise?

A

Inc Cardiac output
In Pulmonary arterial pressure opening apical capillaries
Inc O2 uptake by lungs
Capillary transit time reduces

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30
Q

What 2 types of pressure contribute to formation of tissue fluid

A

Hydrostatic pressure of blood in capillary

Oncotic pressure

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31
Q

What is oncotic pressure?

A

Pressure exerted by plasma proteins in the capillary drawing fluid back into the blood

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32
Q

What influences capillary hydrostatic pressure more, venous pressure or arterial pressure in the systemic circulation?

A

Venous pressure

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33
Q

What increase in pressure leads to peripheral oedema ?

A

Inc Central Venous Pressure

Hypertension doesn’t usually result in peripheral oedema

34
Q

What factor causes a low amount of lymph/tissue fluid produced in the lungs?

A

LOW capillary hydrostatic pressure of capillaries in lungs

35
Q

What is the primary cause of oedema causing capillary pressure to increase?

A

Increased Venous pressure

36
Q

What may lead to Venous pressure increasing leading to pulmonary oedema?

A

Mitral valve stenosis
Left ventricular failure

37
Q

How can Mitral valve stenosis lead to pulmonary oedema?

A

Pressure builds up in Left Atrium
Leads to pressure build up in the pulmonary veins leading to the left atria
Increased pulmonary venous pressure leads to increased capillary/hydrostatic pressure leading too more tissue fluid being filtered out than reabsorbed

38
Q

How can left ventricular failure lead to peripheral oedema?

A

Pressure builds up in the Left Ventricle
Leads to increased pressure in the Left Atrium
Leads to increases pressure in the pulmonary veins
Increased Pulmonary Venous Pressure leads to pulmonary oedema

39
Q

How does Pulmonary Oedema affect gas exchange?

A

Impairs gas exchange

40
Q

How does pulmonary oedema change when standing up and lying down?

A

Changes with hydrostatic pressure (due to gravity)

Forms at bases when standing
Forms throughout lungs when lying down

41
Q

What symptoms does pulmonary oedema cause?

A

Breathlessness

42
Q

How can the symptoms of pulmonary oedema be relieved?

A

Diuretics to minimise fluid retention

43
Q

How does the Cerebral circulation meet the high O2 demand for the brain?

A

High capillary density

High basal flow rate

High O2 extraction

44
Q

Why is a secure blood supply to the brain vital?

A

Neurones very sensitive to hypoxia

Irreversible damage to neurones after 4 mins without oxygen

45
Q

What is an anastomoses?

A

An alternate pathway for blood to flow through in case of a blockage in one of the vessels

46
Q

Structurally how is a secure blood supply to the brain ensured?

A

Anastomoses between basilar and internal carotid arteries

47
Q

What is the main anastomotic structure of the cerebral circulation?

A

Circle of Willis

48
Q

Functionally how is a secure blood supply to the brain ensured?

A

Myogenic auto regulation maintains perfusion during hypotension

Metabolic factors

Brainstem regulating other circulations

49
Q

What is hypercapnia and hypocapnia?

A

High or low partial pressure of CO2

50
Q

How do metabolic factors help secure blood flow to the brain?

A

Cerebral vessels are very sensitive to changes in arterial partial pressure of CO2

51
Q

What happens to cerebral blood vessels in hypercapnia?

A

Vasodilation

52
Q

What happens to cerebral blood vessels in Hypocapnia?

A

Vasoconstriction

53
Q

Why does panic hyperventilation lead to dizziness or fainting?

A

Can cause hypocapnia by expelling lots of CO2
Causes cerebral blood vessels to vasoconstriction reducing blood flow to brain

54
Q

What is the myogenic auto regulated response of the cerebral blood vessels when blood pressure increases?

A

Vasoconstriction

Reduce the blood flow to the brain

55
Q

What is the myogenic auto regulated response of the cerebral blood vessels when blood pressure decreases?

A

Vasodilation

Increase blood flow to brain

56
Q

If there is high activity in the brain what affect does this have on blood flow?

A

Areas with increased neuronal activity = increased blood flow

57
Q

What is metabolic hyperaemia?

A

Increased blood flow to a highly metabolically active area

58
Q

What metabolites act as vasodilators?

A

Increased:
-Partial pressure of CO2
-[K+]
-Adenosine (From ATP breakdown)

Decreased:
-Partial pressure of O2

59
Q

If intercranial pressure increases how is cerebral blood flow affected?

A

Impaired

60
Q

What happens if blood flow to the vasomotor control regions of the brainstem is impaired?

A

Increased sympathetic vasomotor activity
Increases arterial BP
(This helps maintain cerebral blood flow)

61
Q

What baroreceptor reflex is stimulated when blood pressure increases?

A

Reflex bradycardia

62
Q

What does bradycardia + acute hypertension indicate and why?

A

Hall mark of space occupying lesion in brain

Cerebral tumour increases intracranial pressure. This impairs cerebral blood flow. Blood flow to vasomotor control region in brainstem impaired leading to vasoconstriction which increases the BP. This stimulates the bradycardic response

63
Q

What are the 3 main coronary arteries?

A

Right Coronary artery
Left Coronary artery branches into 2:
-Circumflex (Posteriorly)
-Left Anterior Descending (Front) LAD

64
Q

Where do the coronary arteries come from?

A

First branches of aorta

65
Q

When does the left coronary artery mainly flow with blood, systole or diastole?

A

Diastole

66
Q

Why does angina come on during exercise but is relieved by rest?

A

In exercise Diastole period decreases. Left coronary artery mainly has blood flow during diastole, so less blood supplied to heart in exercise causing hypoxia to heart muscle, transient ischaemia causing pain

67
Q

How is the coronary circulation maximised for blood flow?

A

High capillary density (Facilitates efficient O2 delivery)
Very short diffusion distance

68
Q

What factors of the coronary blood vessels help cope with increases myocardial O2 demand?

A

Increased coronary blood flow (proportional up until a point)

Small increase in amount of Oxygen extracted

69
Q

What causes the vasodilation of coronary arteries when demand for oxygen by the heart is high?

A

Metabolic hyperaemia

Adenosine, increased [K+] and lower pH are vasodilators

70
Q

What is a problem with the structure of the coronary arteries?

A

They are end arteries therefore have very few anastomoses

Means if theres a blockage any tissue downstream will die since no alternate route for blood flow

70
Q

What is a problem with the structure of the coronary arteries?

A

They are end arteries therefore have very few anastomoses

Means if theres a blockage any tissue downstream will die since no alternate route for blood flow

71
Q

How do narrowed coronary arteries lead to angina on exercise?

A

Blood flows mostly through coronaries during diastole
Diastole in exercise reduced
This combined with increased demand causes the pain due to hypoxic heart tissue

72
Q

How is skeletal muscles circulation controlled?

A

Capillary density depends on muscle type

Very high vascular tone

Only 1/2 capillaries perfused at rest (means more can be recruited when needed)

73
Q

What metabolites act as vasodilators in skeletal muscle causing metabolic hyperaemia?

A

Inc [K+]
Inc osmolarity
Inorganic phosphates
Adenosine
Inc [H+]

Adrenaline acts on B2 receptors

74
Q

What it’s the special role of cutaneous circulation?

A

Temperature regulation

75
Q

How does cutaneous circulation play a role in temperature regulation?

A

Skin = Main heat dissipating surface

Arterovenous anastomoses

76
Q

What are arterovnous anastomoses?

A

Shunts/blood vessels that pass from arteries to veins to avoid blood flowing close to the surface of the skin

77
Q

What is the main regulator of blood flow through thee cutaneous circulation?

A

Sympathetic stimulation NOT metabolites

Blood flows mainly through arteriovenous anastomoses

78
Q

What happens in terms of sympathetic tone in arterovenous anastomoses when core body temperature decreases?

A

Increased sympathetic tone in arterovenous anastomoses
Decreases blood flow to apical skin

79
Q

What happens in terms of sympathetic tone in arterovenous anastomoses when core body temperature increases?

A

Decreased sympathetic tone in arterovenous anastomoses
Opens the anastomoses allowing blood to divert near to veins near the skin

CVS (21 decks)

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