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HUBS192 Melia > Lecture 12: VENOUS BLOOD FLOW AND THE HEART > Flashcards

Lecture 12: VENOUS BLOOD FLOW AND THE HEART Flashcards

1
Q

Where is the most blood found in humans?

A

In the systemic veins

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2
Q

What do humans have in their circulatory system?

A

More blood than they need

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3
Q

How much blood is stored in the systemic veins?

A

Approximately 2/3

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4
Q

Why can’t the excess blood be in other areas of the circulatory system?

A

Cant be in the heart, pulmonary circuit (too short), arteries (maintaining MAP) or capillaries (too small)

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5
Q

What is the total blood volume in a 70kg human?

A

Approximately 5L

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6
Q

What is CO at rest?

A

Approximately 5L/min

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7
Q

What is arterial pressure at rest?

A

Approximately 100mmHg

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8
Q

What is arterial volume at rest?

A

Approximately 0.7L (13%)

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9
Q

What is venous pressure at rest?

A

Approximately 5mmHg

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10
Q

What is venous volume at rest?

A

Approximately 3.2L (64%)

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11
Q

What is the structure of arteries?

A

Thick and rigid tunica media so no way of allowing extra volume

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12
Q

What is the compliance of arteries?

A

Low

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13
Q

What is the structure of veins?

A

Thin and compliant tunica media so is able to allow extra volume

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14
Q

What is the compliance of veins?

A

high

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15
Q

What is compliance?

A

The extent to which a vessel allows deformation in response to an applied force

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16
Q

What is the formula for compliance?

A

change in volume/change in pressure

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17
Q

What happens in arteries?

A

Large change in pressure results in a small change in volume

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18
Q

What happens in veins?

A

Small change in pressure results in a large change in volume

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19
Q

What do veins have?

A

Survival value

20
Q

What can veins do in an emergency situation?

A

Move blood across to arteries

21
Q

What would happen after an arterial puncture?

A

Loss of arterial blood

22
Q

What would happen after loss of arterial blood?

A

Life threatening fall in arterial pressure

23
Q

What would happen after a life threatening fall in arterial pressure?

A

It will be sensed by the nervous system and venoconstriction will occur

24
Q

What control is venoconstriction under?

A

Neural

25
Q

What happens due to venoconstriction?

A

Veins constrict and push blood froward into the heart and arteries

26
Q

What does high vascular compliance in veins mean?

A

That blood tends to accumulate (pool)

27
Q

What volume is larger?

A

venous volume is larger than arterial volume

28
Q

How is venous volume while supine (lying down)?

A

Uniform from head to toe

29
Q

How is venous volume in the upright position?

A

Below the heart it increases and above the heart it decreases (due to gravity)

30
Q

Where is there extreme venous pooling?

A

In the legs and feet

31
Q

What counteracts venous pooling?

A

Valves and tone of surrounding tissue

32
Q

What does a continuous column have?

A

No valves

33
Q

What happens in a continuous column?

A

Heavy at bottom

34
Q

What does a discontinuous column have?

A

Valves

35
Q

What happens in a discontinuous column?

A

More even distribution of weight

36
Q

What tissue particularly counteracts venous pooling?

A

Skeletal muscle because it can alter its tensile state

37
Q

What varies among individuals?

A

Resting muscle tone

38
Q

What does muscle tone act to do?

A

Stiffen the veins - makes them less compliant and prone to pooling

39
Q

What do some people prone to fainting have?

A

Low muscle tone and excessive venous pooling

40
Q

What does skeletal muscle contractions increase?

A

Venous return to the heart

41
Q

What happens when a muscle contracts?

A

It pushes blood up and down

42
Q

What do valves superior to the contracting muscle do?

A

Open, allowing blood to move to the heart

43
Q

What do valves inferior to the contracting muscle do?

A

Are forced close, preventing back flow of blood to the capillaries

44
Q

What is contracting muscle causing blood to flow to the heart called?

A

The skeletal muscle pump

45
Q

What does increased venous return mean?

A

Increased stroke volume

46
Q

What is starlings law of the heart?

A

The more stretch muscle fibres are before a contraction, the stronger the contraction will be

47
Q

How does a stronger contraction occur (starlings law)?

A

When ventricles fill with more blood because of increased venous return, the thick and thin filaments are pulled further apart so can generate a greater maximum force of contraction

HUBS192 Melia (38 decks)

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