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The Heart > Circulation > Flashcards

Circulation Flashcards

1
Q

What is % CO through the liver

A

27%

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2
Q

What is % CO through the kidney

A

22%

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3
Q

What is % CO through the muscle

A

15%

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4
Q

What is % CO through the brain

A

14%

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5
Q

What is % CO through the skin

A

6%

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6
Q

What is % CO through the bone

A

5%

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7
Q

What is % CO through the heart

A

4%

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8
Q

What is % CO through the rest of the system

A

3.5%

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9
Q

What is % CO through the bronchi

A

2%

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10
Q

What is % CO through the thyroid

A

1%

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11
Q

What is % CO through the adrenal

A

0.5%

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12
Q

Describe the arteries

A

Low resistance

Elastic

Cushion systole

Maintain blood flow to organs during diastole

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13
Q

Describe arterioles

A

Principal site of resistance to vascular flow

Determined by local, neural and hormonal factors

Major role in determining arterial pressure

Major role in distributing flow to tissue/organs

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14
Q

What is myogenic tone

A

Vascular smooth muscle is never completely relaxed

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15
Q

Describe capillaries

A

Slow flow

Flow determined by
- arteriolar resistance
- no. of open pre-capillary sphincters

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16
Q

Describe veins

A

Compliant

Low resistance conduits

Capacitance vessels

Up to 70% of blood flow but only 10mmHg

Valves aid venous return against gravity

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17
Q

Define CO

A

HR x SV

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18
Q

Define BP (MAP)

A

CO x TPR (total peripheral resistance)

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19
Q

Define pulse pressure

A

Systolic - diastolic pressure

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20
Q

Define mean arterial pressure

A

Diastolic pressure + 1/3PP

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21
Q

What governs flow

A

Ohm’s law

Poiseuille’s law

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22
Q

Describe Frank-Starling Mechanism

A

SV increases as end-diastolic volume increases

Due to length-tension (L-T) relationship of muscle

Increase EDV = increase stretch = increase force of contraction

Cardiac muscle at rest is NOT at its optimal length

Increase VR = Increase EDV = Increase SV = Increase CO

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23
Q

Define blood pressure

A

Pressure of blood within and against the arteries

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24
Q

When is blood pressure highest

A

When ventricles contract - systole

100-150mmHg

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25
Q

When is blood pressure lowest

A

When ventricles relax - diastole

60-90mmHg

Not 0 due to aortic valve and aortic elasticity

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26
Q

Define mean arterial pressure

A

D + 1/3(S-D)

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27
Q

What artery is used to measure BP

A

Brachial artery

28
Q

What are the components of BP control

A

Autoregulation

Local mediators

Humoral factors

Baroreceptors

Central (neural) control

29
Q

Describe myogenic autoregulation

A

Stretch of vascular smooth muscle

Contraction until diameter is normalised or slightly reduced

30
Q

What organs have good autoregulation

A

Renal

Cerebral

Coronary

31
Q

What organs have moderate autoregulation

A

Skeletal muscle

Splanchnic

32
Q

What organ has poor autoregulation

33
Q

Local humoral factors - what are the vasoconstrictors

A

Endithelin-1

Internal blood pressure (myogenic contraction)

34
Q

Local humoral factors - what are vasodilators

A

Hypoxia

Adenosine

Bradykinin

NO

K+, CO2, H+

Tissue breakdown products

35
Q

Is NO a vasodilator or vasoconstrictor

A

Vasodilator

36
Q

Circulating hormonal factors - vasoconstrictors

A

Epinephrine (skin)

Angiotensin II

Vasopressin

37
Q

Circulating hormonal factors - vasodilators

A

Epinephrine (muscle)

ANP

38
Q

Describe intrinsic and extrinsic control

A

Intrinsic control dominates to maintain BF to vital organs

Skin - BF vasoconstrictor response to temp (extrinsic)

Skeletal muscle - Dual effects. Rest vasoconstrictor (extrinsic) tone dominant, exercise intrinsic mechanisms predominate

39
Q

Local control - endothelium

A

Essential for control of circulation

Uses NO, prostacyclin, endothelin

40
Q

Is prostacyclin a vasodilator or vasoconstrictor

A

Vasodilator

41
Q

Is endothelin a vasodilator or vasoconstrictor

A

Vasoconstrictor

42
Q

Describe baroreceptors

A

Pressure sensing

Firing rate is proportional to MAP and PP - integrated by the medulla

Increased BP = Increased firing = Increased PNS/Decreased SNS = Decreased CO/TRP = Decreased BP

Vice versa

43
Q

What is the location of baroreceptors

A

Primary (arterial)
- carotid sinus
- aortic arch

Secondary
- veins
- myocardium
- pulmonary vessels

Afferent - glossopharyngeal

Efferent - sympathetic and Vagus

44
Q

What does arterial baroreceptors play a key role in

A

Short term regulation of BP
- minute to minute control
- response to exercise
- haemorrhage

If arterial pressure deviates from norm for more than a few days adapt to a new baseline pressure

45
Q

What is the major factor in long-term BP control

A

Blood volume

46
Q

Describe cardiopulmonary baroreceptors

A

Atria, ventricles, PA

Stimulation - decrease vasoconstriction = decrease BP

Decrease in angiotensin, aldosterone and vasopressin = fluid loss

Play an important role in blood volume regulation

47
Q

Describe the central neural control loop

A

Baroreceptors signal to brain stem

Either + or - sympathetic = + or - vasoconstrictors

Effects HR, SV, vessel diameter

BP + or -

48
Q

Describe arterial baroreceptors affect on central control

A

Increase arterial pressure = increased baroreceptor firing

  • decreased sympathetic outflow to heart, arteries and veins
  • increased sympathetic outflow to heart
49
Q

Describe the role of central chemoreceptors

A

Increase PaCO2 = vasoconstriction - increase peripheral resistance, increase BP

Decrease PaCO2 = decrease medullary tonic activity, Decrease BP

Similar changes with pH

PaO2 less effect on medulla
- decreased = vasoconstriction
- serve decrease = general depression

50
Q

What is the effect of PaO2 mainly by

A

Peripheral chemoreceptors

51
Q

What is the short term control of BP

A

Baroreceptors

52
Q

What is the long term control of BP

A

Volume of blood

Na+, H20, RAAS, ADH

53
Q

Describe the minute by minute feedback loop

A

Blood pressure

Baroreceptor discharge

Sympathetic and Parasympathetic outflow

Vasomotor tone and CO

54
Q

What is the location of chemoreceptors

A

Peripheral
- carotid body
- aortic body

Central
- medulla oblongata

55
Q

Define cushings syndrome

A

Clinical manifestation of pathological hypercortisolism from any cause

56
Q

What circulation do both lungs have

A

Bronchial and pulmonary

57
Q

What is the bronchial circulation

A

Supplied O2 and nutrients to meet metabolic needs

58
Q

What are the adaptations of the pulmonary circulation

A

Low pressure - mean arterial pressure 5-15mmHg

Low resistance

59
Q

What is the mean arterial pressure of the systemic circualtion

60
Q

What are extrinsic controls of cardiovascular system

A

Neural

Hormonal

Reflex

Chemical regulatory mechanisms

61
Q

What do extrinsic factors control

A

Regulate HR

Myocardial contractility

Vascular smooth muscle maintain CO, blood flow distribution and arterial blood pressure

62
Q

What is the role of intrinsic factors of control

A

Vary stroke volume by affecting the myocardial contractility

Can change the sarcomere length or independent of the cell length change using other agents

63
Q

Define Ohm’s Law

A

Pressure gradient/resistance

64
Q

Define Poiseuille’s equation

A

Flow = radius to the power of 4

65
Q

What is the cushings phenomenon

A

NS response to increased intracranial pressure leads to

Increased BP
Irregular breathing
Brachy cardia

66
Q

What are the constituents of plasma

A

91.5% water

7% proteins

67
Q

Describe plasma proteins

A

Carrier proteins e.g. albumin, globulin

Immunoglobulins

Clotting factors

The Heart (12 decks)

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