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HUBS192 > Lecture 12 Venous blood flow and the heart > Flashcards

Lecture 12 Venous blood flow and the heart Flashcards

1
Q

Arterioles

A

Decide the direction of blood flow at parallel part of systemic circuit

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2
Q

Blood back from left side of heart to right side of heart

A

To become reoxygenated

veins

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3
Q

Left side of heart

A

In charge of Cardiac output

The amount of flow of blood out

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4
Q

Right side of heart

A

Venous return

The amount of blood flow back in

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5
Q

Where is most blood found?

A

Systemic veins

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6
Q

what is the total blood volume in 70kg human?

A

5L

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7
Q

Distribution of blood in systems

Small amounts in

A

Pulmonary circuit 9%
Heart 7%
Systemic arterial system 13%
Systemic capillaries 7%

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8
Q

Distribution of blood in systems

Majority of blood in

A

Systemic venous system 64%

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9
Q

Why are there large amounts of blood in the veins?

A

Need extra blood to survive

meet the demand of organs (oxygen and nutrient)

If we get an injury lose some blood, and only just have enough the injury will be life threatening

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10
Q

Places where you can’t store extra blood

incl why

A

Heart (Packed has no space)

Pulmonary circuit (short busy to get blood to lungs to become oxygenated)

Arteries (MAP will increase)

Capillaries (tiny no room)

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11
Q

Blood volume and blood pressure distribution at rest

Arteries

A

High pressure

Low volume

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12
Q

Blood volume and blood pressure distribution at rest

Veins

A

Low pressure

High volume

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13
Q

How do veins store more blood at lower pressure?

A

Thin walls
More compliance
Structure

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14
Q

Artery

incl media, structure

A

Thick Tunica media

Rigid (more muscle)

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15
Q

Veins

incl media, structure, muscle

A

Thin Tunica media

Less muscle

More compliance

Flexible accommodate more blood

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16
Q

Compliance

A

The extent to which a vessel allows deformation in response to an applied force to accommodate more blood.

More = flexible

Less = rigid

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17
Q

Compliance equation

A

ΔV / ΔP

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18
Q

Artery compliance

A

Shape maintained as pressure increases,

small change in volume

Less compliant

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19
Q

Vein Compliance

A

At low pressure
- Collapse (drained blood)

Increase pressure (Put blood in vein)

Volume increases

Very compliant

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20
Q

Why is Most blood found in small veins and venules?

A

Compliant
More flexible to accommodate extra blood
Able to store blood in that area

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21
Q

Veins have

A

survival value

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22
Q

Survival value

A

eg Veins have a Pool of blood that you can use when needed

eg puncture small artery

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23
Q

Cut / puncture small artery

what happens, what senses injury, what occurs, what goes back up

A

Loss of arterial blood
Lose blood pressure

Brain senses the injury

Venoconstriction

Veins squeezes on the blood that it’s storing (at higher pressure to the heart)

Under neural control medium and larger veins replaces the blood to the artery

MAP goes back up

24
Q

Vasodilation

A

Luminal radius of arterioles increase

25
Q

Vasoconstriction

A

Luminal radius of arterioles decrease

26
Q

MAP constant

A

Total blood flow increased

TPR decrease

27
Q

High vascular compliance means that

A

blood tends to accumulate (pool) in veins

28
Q

Supine (laying down)

venous volume, gravity

A

Venous volume uniform (equal) from head to toe

Blood evenly distributed not working against gravity

29
Q

Upright position from supine (no moving muscles)

venous volume below & above heart, Pooling, Arteries, Veins, gravity

A

Venous volume below heart increases

Venous volume above heart decreases

Extreme venous pooling in legs and feet

Arteries remain same shape (high pressure low compliance)

Veins (high compliance low pressure) gravity pulls blood downward causes pooling

Veins at bottom collecting too much blood expanded and not getting the blood back to top.

30
Q

What counteract venous pooling?

A

Venous valves

Tone of surrounding tissue (skeletal muscle)

31
Q

To prevent pooling in veins

A

Venous valves

Tone of surrounding tissue

32
Q

No valves in veins causes

A

Pooling due to gravity

33
Q

Venous valves

A

(unidirectional flow) in medium veins towards heart

  • Even distribution in each section
  • Prevents backflow
34
Q

Tone of surrounding tissue

A

Skeletal muscle supports veins to prevent too much blood collecting at bottom

Puts pressure on the vein to keep its shape and prevent pooling

35
Q

Poor muscle tone

A 
Elderly
Prone to fainting
Veins not supported
Pooling 
Doesn’t get to heart
Poor circulation
Blood doesn’t get to brain
36
Q

What increases venous return to the heart?

A

Skeletal muscle contractions

37
Q

Skeletal muscle contraction

A

Squeeze veins and pushes blood upwards through valves, valves prevent going downwards

Increase blood flow in veins back towards the heart

38
Q

Diaphragm

A

Large muscle

Rises and falls as we breathe

39
Q

Intercostal muscles

A

Between ribs
Constrict and expand as we breathe
Supports veins

40
Q

More that we breathe the more the diaphragm goes down and the more the intercostal muscles expand and contract and the

A

veins as we breathe are being squeezed on and is pushing blood up towards the heart

41
Q

Exercising

A

Using muscles

Squeezing on veins

Breathing faster (diaphragm up and down)

Intercostal muscles in and out

Squeezing on veins in chest
Increases the amount of blood returning to the veins

42
Q

Increased venous return means

A

increased stroke volume

43
Q

Starling’s Law

A

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

The more blood returned to the heart the more comes out for each beat
Pendent on the strength of the beat

44
Q

Cellular mechanism of cardiac contraction

A

Actin and myosin filaments

Myosin heads grab on to actin and pull when calcium is released

45
Q

Contracted sarcomere

A

Myosin heads grab on to actin and pull when calcium is released

To the last head last place where it can pull (defines strength of contraction, and amount of blood pushed out)

46
Q

Maximum contraction

A

Space between the actin filament and last myosin head

47
Q

What happens when we return more blood to the heart through the veins?

A

Heart expands to accommodate extra blood
Walls of expands with it

Sarcomeres stretched out

More space for myosin and actin to interact

Maximum contraction increases

Pushes more blood out of the system

48
Q

Starling

A

More blood returned to the heart through the veins the more volume of blood pack into the heart before the contraction. Causes the walls to expand and gives a stronger contraction

49
Q

More ventricular volume before the contraction (end of diastole)

A

The larger the contraction,

The larger the stroke volume (volume of blood that comes out of the heart with each heartbeat)

50
Q

More blood return

A

More blood packed in

Bigger heart

Stronger contraction

More stroke volume

51
Q

Supine

A

Veins aren’t working against gravity

Getting really good return to the heart through the veins

52
Q

Tilted upwards

A

Not using muscles

Nothing to push the blood to the heart

Extra pooling due to gravity

Less return

53
Q

Reduce return of blood

A

Smaller contraction

Diastolic volume of blood (before contraction) smaller

Smaller volume of blood before contraction

Smaller stroke volume during contraction

54
Q

Starling’s law of the heart

A

the more the walls of the heart stretch prior to contraction,

the stronger a contraction and greater stroke volume

55
Q

venous return directly affects

A

the stroke volume and performance of the heart.

HUBS192 (36 decks)

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