Haemodynamics

Question 1

What is the difference between plasma and serum?

Answer 1

Plasma is fluid collected from unclothed blood whereas serum is the fluid collected from clotted blood

Question 2

What is the most common cause of increased plasma viscosity?

Answer 2

Multiple myeloma

Question 3

What is the name given to an increase in red blood cells?

Answer 3

Polycythaemia

Question 4

What is the term given to an increase in platelet levels?

Answer 4

Thrombocytosis

Question 5

What is the name given to increased white blood cells?

Answer 5

Leukaemia

Question 6

Increased RBCs, platelets and WBCs can all lead to what?

Answer 6

Increased whole blood viscosity and sludging of blood in peripheries

Question 7

How can MINOR changes in plasma viscosity occur?

Give three examples

Answer 7

Raised levels of acute phase proteins
e.g. Fibrinogen
Complement factors
CRP (c-reactive protein)

Question 8

What substance can be used clinically as a measure of inflammation?

Answer 8

C-reactive protein (CRP)

Question 9

What is the difference between laminar and turbulent flow?

Answer 9

Laminar:
Streamline flow of blood with each layer remaining the same distance from the blood vessel wall
Turbulent:
Blood flowing in all directions in the vessel and continually mixing as a result of an obstruction, increased resistance, the rate of blood flow being too great

Question 10

What causes a pulse?

Answer 10

The shock wave produced by distension of the aortic wall and the compliment vessels it then travels down. It arrives slightly before the blood itself

Question 11

What is the difference between the flow and the velocity of blood?

Answer 11

The flow is the movement of a volume of blood over time whereas the velocity is the distance moved by an object over time

Question 12

When laminar flow occurs, where in the vessel is the velocity of blood the greatest?

Answer 12

In the centre of the vessel compared to the outer edge, creating a parabolic profile

Question 13

A strong pulse is often described as what?

Answer 13

“Bounding”

Question 14

Reduced pulse volume can result from what?

Answer 14

Left ventricular failure
Aortic valve stenosis
Hypovolaemia

Question 15

Reduced pulse volume is often described as what?

Answer 15

“Thready”

Question 16

What does bradycardia do to the pulse pressure and how does this relate to the pulse that is felt?

Answer 16

It widens pulse pressure and leads to a bounding pulse

Question 17

How does lowering peripheral resistance affect diastolic pressure and pulse pressure?

Answer 17

It lowers diastolic pressure

Therefore increasing pulse pressure

Question 18

Name three things that lower peripheral resistance?

Answer 18

Hot bath
Exercise
Pregnancy

Question 19

Serum = plasma - _______________

Answer 19

Clotting factors (fibrinogens)

Question 20

What kind of profile does laminar flow produce?

Answer 20

Parabolic profile

Question 21

What can cause turbulent flow in a blood vessel?

Answer 21

Sharp turn
Rough surface
Increased resistance to blood flow

Question 22

Pulse pressure= ___________-_____________

Answer 22

Systolic pressure - Diastolic pressure

Question 23

What is an general, average measurement of pulse pressure?

Answer 23

40mmHg

Question 24

Mean arterial pressure is measured how?

Answer 24

Diastolic pressure + 1/3 Pulse pressure

Question 25

Below what value is mean arterial pressure (MAP) considered to impair organ perfusion?

Answer 25

MAP below 70mmHg

Question 26

Retrograde flow of blood in the arterial system is greatest when what feature is high?

Answer 26

Resistance

Question 27

If the blood vessels lose their compliancy they cannot do what?
What might be a cause of this?

Answer 27

Transmit a shock wave, no pulse will be felt

Caused by calcification of the arterial wall

Question 28

Resistance vessels are found on which side of the circulatory system?

Answer 28

Arteriolar side (arterioles)

Question 29

What is the role of resistance vessels in the circulatory system?

Answer 29

To restrict blood flow to drive supply to areas of the body that are hard to perfuse

Question 30

On which side of the circulatory system are capitance vessels found?

Answer 30

The Venous return side

Question 31

What is the role of capitance vessels within the circulatory system?

Answer 31

To enable the system to vary the amount of blood pumped around the body

Question 32

The circulation acts as two pumps in series, what are these two pumps?
How does the pressure within these two pump system vary?

Answer 32

The systemic circulation (high pressure)

The pulmonary circulation (low pressure)

Question 33

Systole is what?

Answer 33

Contraction and ejection of blood from the ventricles

Question 34

Diastole is what?

Answer 34

Relaxation and filling of the ventricles

Question 35

What is the usual value for stroke volume for each ventricle?
Given this value, what is the amount of blood pumped by the heart in a minute?

Answer 35

Around 70ml per beat

@ 70bpm, amount pumped in 1 minute= 5L of blood

Question 36

Describe the structure of cardiac muscle and how it compares to other muscle types

Answer 36

Specialised, striated muscle made up on individual cells (cardiac myocytes)
Somewhere between skeletal and smooth muscle

Question 37

How do cardiac myocytes communicate with each other?

Answer 37

They are interconnected electronically by gap junctions

Question 38

How does the action potential across the membrane of cardiac myocytes differ from action potentials in other cells?
Why is this the case?

Answer 38

The AP is longer in cardiac myocytes (around 280ms)

One AP is driving one beat of the heart, needs to be long enough to sustain the beat

Question 39

What determines whether the valves of the heart are open or closed?

Answer 39

The difference in pressure across the valves

Question 40

What structures prevent the inversion of valves on systole?

What are these structures connected to to give them their strength?

Answer 40

Chordae Tendineae

Papillary muscles