Arterial system and haemodynamics

Question 1

Where is arterial blood pressure determined?

Answer 1

In the elastic arteries

Question 2

Where will you find pulsatile pressure?

Answer 2

In the aorta and large arteries

Question 3

What does the aorta do to pulsatile pressure? And why?

Answer 3

Dampens pulsatile pressure
Ensure continuous flow into the circulation
Ensures blood pressure is maintained during diastole

Question 4

How do you calculate pulse pressure?

Answer 4

Systolic pressure - diastolic pressure

Question 5

How do you calculate mean arterial blood pressure?

Answer 5

(SP-DP)/3 + DP

Question 6

What happens to the elastic wall during systole?

Answer 6

It distends

Energy is stored

Question 7

What happens to the elastic wall during diastole?

Answer 7

It recoils

Blood propelled forwards

Question 8

What limits how fast blood can move through arteries?

Answer 8

Systemic vascular resistance

Question 9

Where is pressure lowest?

Answer 9

In the veins

Question 10

What 3 factors determine resistance to blood flow in a single vessel?

Answer 10

Vessel length
Blood viscosity
Radius

Question 11

What determines the viscosity of blood?

Answer 11

The hematocrit

Question 12

What is the hematocrit?

Answer 12

The ratio of red blood cells to volume of blood

Question 13

What could alter the hematocrit?

Answer 13

Anaemia
Altitude
Dehydration
Pregnancy

Question 14

Describe laminar flow

Answer 14

Flow in straight line
Normal pattern of flow
Highly efficient
Follows Poiseuille’s Law

Question 15

Where does blood flow fastest?

Answer 15

In the middle

Question 16

Describe turbulent flow

Answer 16

Occurs where flow velocity is high
Inefficient
Cannot apply Poiseuille’s law

Question 17

What might cause turbulent flow?

Answer 17

Large artery branches
Pregnancy
Exercise
Valve defects
Arterial stenosis

Question 18

How does arterial stenosis lead to turbulent flow?

Answer 18

Arterial stenosis reduces area of valve

Blood is ejected at a higher velocity

Question 19

What two things determine arterial blood pressure?

Answer 19

Blood volume in the arterial system (cardiac output)

Resistance to blood flow (total peripheral resistance

Question 20

How do you calculate arterial blood pressure?

Answer 20

Cardiac output x total peripheral resistance

Question 21

What determines systolic pressure?

Answer 21

Stroke volume
Aortic/arterial distensibility
Ejection velocity
Diastolic pressure of previous beat

Question 22

What determines diastolic pressure?

Answer 22

Arteriolar resistance

Very high heart rate

Question 23

What affect does ageing have on blood pressure?

Answer 23

Older persons vessels have lost elasticity
Loss of elastin
No distension so pressure increases during systole
No recoil during diastole so diastolic pressure decreases
Widened pulse pressure

Question 24

What affect does vasodilation have on flow?

Answer 24

Increases flow

Question 25

What affect does vasoconstriction have on flow?

Answer 25

Decreases flow

Question 26

What is normal tone of blood vessels?

Answer 26

Slightly constricted

Question 27

What controls vasoconstriction and vasodilation?

Answer 27

Endothelial factors
Local mechanisms
Central neural mechanisms
Hormonal mechanisms

Question 28

What does constriction of arterioles to one organ result in?

Answer 28

Decreases flow to that organ only

Question 29

What does constriction of arterioles to multiple organs result in?

Answer 29

An increase in total peripheral resistance

Therefore an increase arterial blood pressure

Question 30

When might constriction of arterioles to multiple organs be necessary?

Answer 30

Standing

Haemorrhage

Question 31

Give examples of local factors that control flow

Answer 31

Metabolic mechanisms
Myogenic mechanisms
Autoregulation (both the above)

Question 32

What nervous system is responsible for vasomotor tone?

Answer 32

Sympathetic nervous system

Question 33

What does an increase in sympathetic nervous activity result in?

Answer 33

Vasoconstriction