3 Haemodynamics

Question 1

What is serum?

Answer 1

Plasma without clotting factors

Question 2

Does blood viscosity change?

Answer 2

Overall blood viscosity is relatively constant

Plasm viscosity undergoes acute changes locally

Question 3

What is haemodynamics?

Answer 3

The movement of blood dictated by the metabolic demands of the body

Question 4

Describe the movement of blood in terms of pressure

Answer 4

Moves from high pressure to low pressure

Question 5

What are the 2 types of blood flow?

Answer 5

Laminar flow

Turbulent flow

Question 6

What is laminar flow?

Answer 6

Blood flow that maintains its energy and is smooth, silent, streamlined and regulated

Question 7

Where does blood move fastest and slowest during laminar flow and why?

Answer 7

Fastest - Centre of the blood vessel

Slowest - edge of the blood vessel as there is the most resistance here

Question 8

What is turbulent flow?

Answer 8

Blood flow that loses it’s energy and is disorganised/irregular and noisy

Question 9

Why does turbulent flow occur?

Answer 9

Change in the vessel diameter

Question 10

Why is lost during turbulent flow?

Answer 10

The pressure of the increases beyond which flow can match it linearly

Question 11

Where does turbulent flow typically occur?

Answer 11

Stenosed arteries

Where vessels branch off (changing dricetion of vessels)

Question 12

What is flow?

Answer 12

Volume transferred per unit time

Question 13

What is the unit of flow?

Answer 13

L/min

Question 14

What is pressure?

Answer 14

Force per unit area

Question 15

What is the unit of pressure?

Answer 15

Pascal

Question 16

What other unit is used to measure blood pressure?

Answer 16

mmHg (mm of mercury)

Question 17

What is conductance?

Answer 17

measure of ease of flow

Question 18

What is resistance?

Answer 18

measure of difficulty of flow

Question 19

What is the relationship between conductance and resistance?

Answer 19

Reciprocal/inverse

R = -(1/K)

Question 20

What is Darcy’s law?

Answer 20

Flow = Pressure gradient / resistance
OR
Flow = Conductance x Pressure gradient

Question 21

How does the body change blood supply to organs?

Answer 21

Change resistance

Question 22

Why cant the body alter blood supply to organs via pressure?

Answer 22

Pressure is tightly regulated, as resistance is tightly regulated

Question 23

What factors could POTENTIALLY alter the resistance to flow?

Answer 23

Diameter of blood vessel
Length of blood vessel
Viscosity of blood

Question 24

Which factors DO alter resistance to flow?

Answer 24

Diameter of blood vessel - lumen size

Question 25

What is the relationship between flow and radius of blood vessel?

Answer 25

Directly proportional | Changes impact flow by the 4th power

Question 26

What is the relationship between resistance and diameter, length of vessel and viscosity?

Answer 26

R=8nL/Πr^4

Question 27

Why is resistance in the aorta low?

Answer 27

Short length, large diameter

Question 28

Which vessel contribute the greatest peripheral resistance?

Answer 28

Small arteries and arterioles

Question 29

Where is resistance lower, in the pulmonary or systemic circulation? Why? What anatomical feature of the heart demonstrates this?

Answer 29

Pulmonary circulation, as vessels are wider and shorter. Left ventrical is thicker than rigth ventrical a it pumps blood to the systemic circulation, which has more resistance than the pulmonary circulation that the right ventricle pumps blood to

Question 30

Define velocity and give units

Answer 30

Distance a fluid moves in a given time (cm/s)

Question 31

How are flow and velocity related?

Answer 31

Flow = Corss sectional area x velocity

Question 32

What is the relationship between velocity and r^2

Answer 32

inversely related

Question 33

Why is velocity slower at capillaries and why is it useful?

Answer 33

Capillaries have a large cross sectional area, velocity is inversely related to area, so slow velocity. This is useful for gas exchange, as it gives gases a longer time for diffusion to occur.

Question 34

What is the equation for pulse pressure?

Answer 34

Peak systolic blood pressure - end diastolic blood pressure

Question 35

What is the equation for mean arterial pressure (MAP)?

Answer 35

End diastolic blood pressure - ((Peak systolic blood pressure - End diastolic blood pressure)/3) OR DBP - 1/3 Pulse pressure OR pressure gradient = resistance x flow OR Cardiac output x total peripheral resistance

Question 36

Below which blood pressure does organ perfusion become impaired?

Answer 36

70mm/hg

Question 37

What is cardiac output? How is the pressure gradient measured? How is resistance measured in mean arterial pressure? How does this give you the equation for mean arterial pressure?

Answer 37

The amount of blood being ejected from the hear in one given systole Mean Aortic Pressure - Central Venus Pressure Systemic resistance is equilvalent to the Total Peripheral resistance

Question 38

What is the value of central venous pressure?

Answer 38

Almost 0

Question 39

How is cardiac output measured?

Answer 39

Stroke volume x Heart rate

Question 40

What is an average systolic blood pressure?

Answer 40

90mm/Hg