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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
Vasoconstriction
Luminal radius of arterioles decrease
26
MAP constant
Total blood flow increased | TPR decrease
27
High vascular compliance means that
blood tends to accumulate (pool) in veins
28
Supine (laying down) | venous volume, gravity
Venous volume uniform (equal) from head to toe | Blood evenly distributed not working against gravity
29
Upright position from supine (no moving muscles) | venous volume below & above heart, Pooling, Arteries, Veins, gravity
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
What counteract venous pooling?
Venous valves Tone of surrounding tissue (skeletal muscle)
31
To prevent pooling in veins
Venous valves Tone of surrounding tissue
32
No valves in veins causes
Pooling due to gravity
33
Venous valves
(unidirectional flow) in medium veins towards heart - Even distribution in each section - Prevents backflow
34
Tone of surrounding tissue
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
Poor muscle tone
``` Elderly Prone to fainting Veins not supported Pooling Doesn’t get to heart Poor circulation Blood doesn’t get to brain ```
36
What increases venous return to the heart?
Skeletal muscle contractions
37
Skeletal muscle contraction
Squeeze veins and pushes blood upwards through valves, valves prevent going downwards Increase blood flow in veins back towards the heart
38
Diaphragm
Large muscle | Rises and falls as we breathe
39
Intercostal muscles
Between ribs Constrict and expand as we breathe Supports veins
40
More that we breathe the more the diaphragm goes down and the more the intercostal muscles expand and contract and the
veins as we breathe are being squeezed on and is pushing blood up towards the heart
41
Exercising
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
Increased venous return means
increased stroke volume
43
Starling’s Law
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
Cellular mechanism of cardiac contraction
Actin and myosin filaments Myosin heads grab on to actin and pull when calcium is released
45
Contracted sarcomere
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
Maximum contraction
Space between the actin filament and last myosin head
47
What happens when we return more blood to the heart through the veins?
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
Starling
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
More ventricular volume before the contraction (end of diastole)
The larger the contraction, The larger the stroke volume (volume of blood that comes out of the heart with each heartbeat)
50
More blood return
More blood packed in Bigger heart Stronger contraction More stroke volume
51
Supine
Veins aren’t working against gravity Getting really good return to the heart through the veins
52
Tilted upwards
Not using muscles Nothing to push the blood to the heart Extra pooling due to gravity Less return
53
Reduce return of blood
Smaller contraction Diastolic volume of blood (before contraction) smaller Smaller volume of blood before contraction Smaller stroke volume during contraction
54
Starling’s law of the heart
the more the walls of the heart stretch prior to contraction, the stronger a contraction and greater stroke volume
55
venous return directly affects
the stroke volume and performance of the heart.

HUBS192 (36 decks)

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