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Cardiovascular System > Pressure and Flow in Arteries and Veins > Flashcards

Pressure and Flow in Arteries and Veins Flashcards

1
Q

What is the main method used for measurement of arterial pressure?

A

Auscultation of Karotkoff sounds using spygomanometer and stethoscope.

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2
Q

What sound is heart when cuff pressure is just less than systolic pressue?

A

tapping

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3
Q

What sound is heard when cuff pressure is between diastolic and systolic pressure?

A

a thumping sound

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4
Q

What sound is heard when cuff pressure is the same as diastolic pressure?

A

a muffled sound, often inaudible though

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5
Q

What are the advantages of auscultation of Korotkoff sounds using sphygomomanometer and stephoscope? (2)

A

Non-invasive

Cheap

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6
Q

What are disadvantages of auscultation of Korotkoff sounds using sphymomanometer and stephoscope? (3)

A

Accuracy

Discontinuous

Needs care

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7
Q

What do elastic arteries act as?

A

Pressure reservoirs that damp down pressure variants.

prevents pressure getting too high in systole and too low in diastole

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8
Q

What factors affect the pressure wave for blood in arteries? (4)

A

Stroke volume

Velocity of ejection

Elasticity of arteries

Total peripheral resistance

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9
Q

What is normal arteriolar pressure?

A

120/80mmHg

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10
Q

How does normal arteriolar pressure change with age?

A

It increases, as blood vessels lose elasticity.

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11
Q

The aorta _______ energy during systole and ________ energy during diastole.

A

absorbs

releases

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12
Q

Which factors affect the rising phase of the pressure wave?

A
  • velocity of projection
  • SV
  • HR
  • strength of contraction
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13
Q

Which factors affect the falling phase of the pressure wave?

A
  • elasticity of arteries

- TPR

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14
Q

What happens at the dicrotic notch in the pressure wave?

A
  • isovolumetric relaxation

- small and brief increase in arterial pressure due to closing of aortic valve.

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15
Q

In one word, what happens to pressure in blood vessels moving from the arteries all the way through to the veins?

A

it decreases

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16
Q

Between which two types of vessels is the decrease in pressure the greatest?

Explain this.

A

Arteries to arterioles.

Arterioles, the resistance vessels, have smaller diameters and overall larger surface area which reduces the pressure force.

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17
Q

Pulse pressure = ______ - ________

A

systolic pressure - diastolic pressure

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18
Q

There is a _______ _______ in pressure through arteries (from about __ to __ mmHg).

A

small decrease

95 to 90

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19
Q

There is a _____ drop through arterioles (from about __ to __ mmHg)

  • the _________ vessels
A

large
90 to 40

resistance

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20
Q

How would you describe pressure in the capillaries?

Why is this good?

A

low, 20-40 mmHg

Because capillaries are extremely thin walled and fine.

21
Q

Leaving the capillaries, a ______ pressure difference remains pushing blood back through the ______ (from around __ to __ mmHg).

This is known as the _______ ________ pressure, which returns blood to the ______ ______ of the heart.

A

small
veins
20 to 5

systemic filling
right side

22
Q

Why is there only a small drop in pressure through arteries?

A

Low resistance conduit, elasticity releases energy

23
Q

How does pulmonary circulation pressure compare to systemic circulation?

A

1/5th the size, same curve

24
Q

What is the velocity of blood flow related to?

Which vessels is it fastest/slowest in?

A

Total cross sectional area

Fastest in aorta/arteries, slowest in capillaries.

25
Q

How does velocity of blood flow relate to total cross sectional area?

A

Greater the total cross sectional area, the smaller the velocity.

26
Q

What is the systemic filling pressure?

A

The pressure of blood exiting the circulatory system.

27
Q

Which of the two ventricles has the lower pressure?

Why?

A

RV

Less pressure required to push blood through the pulmonary circulation.

28
Q

Why do external influences affect flow in veins?

A

Due to their thin walls, they are distensible and collapse.

29
Q

What effect does gravity not have on pressure and flow between arteries and veins?

A

It does not affect the pressure gradient, as it is acting on both arteries and veins.

30
Q

Where is venous distension caused by gravity most likely to happen?

What is the clinical term for this?

What effect does this have on the heart?

A

Legs

Orthostatic hypotension

  • decreased EDV
  • decreased preload
  • decreased SV
  • decreased CO
  • decreased MAP/afterload
31
Q

The height of jugular collapse can be used to estimate ______.

A

Central venous pressure

32
Q

If there is a high CVP, the jugular vein collapse will happen ______.

A

higher

33
Q

Explain the concept of jugular venous collapse.

A
  • jugular vein height increase = decrease in pressure
  • pressure becomes sub-atmospheric
  • venous distension
  • High CVP, collapse occurs higher in neck
34
Q

What are examples of external factors that affect flow in veins? (5)

Which of these is the main driving force for venous return to the heart?

A
  • Gravity
  • Skeletal muscle pump
  • Respiratory pump
  • Venomotor tone
  • Systemic filling pressure

Systemic filling pressure

35
Q

What can gravity cause in terms of flow through veins?

A

Venous distension in legs

Venous collapse in neck

36
Q

How does the skeletal muscle pump work?

A

Skeletal muscle contracting in a rhythmic fashion helps pump blood back from the peripheries, as valves prevent blood moving away from the heart.

37
Q

What are examples of skeletal muscle pump impacting venous flow?

A

Rhythmic vs static exercise
Hot guardsmen
Deep vein thrombosis
Varicose veins

38
Q

How does venomotor tone affect pressure and flow in veins?

A

Contraction of smooth muscle round the veins helps to mobilise capacitance and increase EDV.

39
Q

Describe how the respiratory pump changes the flow in veins?

A
  • Inspiration = negative pressure in thorax/positive pressure in abdomen
40
Q

What does clotting involve?

A

Formation of a platelet plug.

Formation of a fibrin clot.

41
Q

What are the anti-clotting mechanisms of the endothelium aiming to do?

A
  • prevent platelet plug
  • prevent fibrin clot
  • break down developed clots
42
Q

Outline the anti-clotting mechanisms of the endothelium.

A
  • physical barrier (no platelet aggregation)
  • prostacyclin and NO production
  • produces TF pathway inhibitor
  • expresses thrombomodulin
  • expresses heparin
  • secretes tissue plasminogen activator.
43
Q

What do prostacyclin and NO do?

A

inhibit platelet aggregation

44
Q

What does TFPI do?

A

stops thrombin production

45
Q

What does thrombomodulin do?

A

binds thrombin & inactivates it.

46
Q

What does heparin do?

A

also inactivates thrombin

47
Q

What does tissue plasminogen activator do?

A

Catalyses the reaction of plasminogen to plasmin, and plasmin digests the clot.

48
Q

What is converted into fibrin and what carries this out?

A

fibrinogen

thrombin

Cardiovascular System (37 decks)

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