Pressure & Flow in Arteries & Veins Flashcards

1
Q

How do we measure BP?

A

A sphygmomanometer to measure BP
A stethoscope to auscultate korotkoff sound below the cuff in order to tell systole vs diastole.

Automatic cuffs are becoming common so you dont need to auscultate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

How do we distinguish between systole/dyastole?

A

At a certain cuff pressure it will contrict the dyastolic flow but systolic pressure is still high enough to pass through without trouble. Therefore you will hear a continuous muffled sound or thumping to show dyastole.
At a higher pressure it will completely constrict dystolic pressure and somewhat constrict systolic pressure so you will hear tapping in time with systole showing your at the systolic pressure.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are the pros/cons to measuring BP with a sphygmomanometer??

A

Pros- Non invasive & Cheap
Cons - Inaccurate, Discontinuous and takes care

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Whats the function of elastic arteries?

A

To dampen any pressure variations, acting as a “pressure reservoir”

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What effects the arterial pressure wave?

A
  • SV
  • Ejection Velocity
  • Elasticity of Arteries
  • TPR
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How does ejection velocity effect the arterial pressure wave?

A

A higher ejection velocity means the elastic arteries have less time to react & stretch so a higher peak pressure is reached

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How does TPR effect arterial pressure wave?

A

If TPR all the pressures go down (MAP = CO x TPR)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Why does pressure decrease in the vessels during/after arterioles?

A

They have a high resistance which you would think would increase pressure (Pressure = flow x resistance)
However this resistance decreases flow so so each consecutive section of arteriole and the following vessels has a lower flow and therfore pressure.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What do we call the pressure difference pushing pressure difference driving blood back through veins?

A

Systemic Filling Pressure (quite small ~5-20mmHg)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Why are external influences able to affect flow in veins?

A

Because theyre very distensible/collapsible.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What external factors effect the pressure & flow of veins?

A

Gravity
The SkeletalMuscle Pump
Respiratory Pump
Venomotor Tone
Systemic Filling Pump

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Why doesnt gravity effect the pressure driving blood from arteries -> veins?

A

Because it evenly effects the veins and arteries so the pressure difference is unchanged

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How does gravity effect he veins?

A

Venous distension in the legs and collapse in the head/neck.
Pressure in the veins above the heart can become sub-atmospheric and the legs can go as much as 80mmHg higher.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

venous distension in the legs can lead to postural/orthostatic hypotension, how?

A

Venous distension in legs
-> Reduced Venous Return
-> Reduced EDV
-> Reduced Preload
-> Reduced SV
-> Reduced CO
-> Reduced MAP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Whats the use of measuring the level of jugular collapse?

A

It can be used to estimate CVP (just well enough to tel if its roughly normal or not)
Level of jugular collapse is basically how high above the heart does the pressure become subatmospheric and the vein collapse

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How does the skeletal muscle pump work?

A

Every time it contracts it squashes the vein pushing blood in the right direction thanks to valves.
This is particularly important in the legs to counter venous distension

17
Q

What effect do rythmic vs static exercise have on the veins?

A

Rythmic exercise involves lots of contractions so lots of blood is pumped through the veins by the skeletal muscle pump.
Static exercise like weight lifting involves a sustained contraction which stops blood flow through the veins

18
Q

What happens if you sit or stand still for long periods without contractions?

A

Deep vein Thrombosis can occur, hence why fliers and palace guards are told to move about periodically.

19
Q

What is the effect of long term venous distension (for years)

A

Varicose veins

20
Q

What is the respiratory pump?

A

Every time you inhale you increase abdominal presure and decrease thoracic presssure.
This pushes and pulls (respectively) blood through veins from the abdomen into the heart.
The deeper the breath the more blood flow.

21
Q

What is venomotor tone?

A

The level of sustained contraction in smooth muscle surrounding veins and venules.

22
Q

how does venomotor tone change during exercise?

A

It increases during exercise or flight/flight so the muscle contracts and pushes blood back to the heart

23
Q

What creates systemic filling pressure?

A

The contraction of the left ventricle, its transmitted through the whole vascular tree to the veins.
Its the main force pushing blood back to the heart at rest.

24
Q

How do the veins themselves affect the next systemic filling pressure?

A

Very dilated veins pump less blood to heart
Therefore theres a smaller CO and a lower pressure produced
This means the systemic filling pressure gets lower.

25
Q

How does pressure change through the major arteries ?

A

thers a small drop as theyre a low resistance conduit,
~95 to 90 mmHg

26
Q

how does pressure change through the arterioles?

A

A big drop as theyre resistance vessels
From ~90mmHg to 40mmHg

27
Q

Why is it important blood pressure is low upon reaching the capillaries?

A

Theyre v thin walled so a high pressure would burst them?

28
Q

What is the value of systemic filling pressure?

A

~5-20mmHg

29
Q

How do the pressures of pulmonary circ compare to systemic circ?

A

Pulmonary circulation has pressure about 1/5 of systemic.

30
Q

What determines velocity in the vessels?

A

The total cross section of the vessels, hence its lowest in the capillaries and fastest in the aorta/vena Cavae.