Pressure and Flow in Arteries

Question 1

What is the main method used for measurement of arterial pressure?

Answer 1

Auscultation of Korotkoff sounds using sphygmomanometer and stethoscope

Question 2

What is the function of elastic arteries?

Answer 2

Act as a pressure reservoir to dampen down pressure variations (prevents pressure getting too high in systole and too low in diastole)

Question 3

What is the pressure wave affected by?

Answer 3

Stroke volume
Velocity of ejection
Elasticity of arteries
Total peripheral resistance

Question 4

What is the ‘normal’ arterial pressure?

Answer 4

120/80 mmHg

Question 5

What happens to arterial pressure with age?

Answer 5

It increases as blood vessels lose elasticity

Question 6

What happens to pressure in blood vessels moving from the arteries all the way through to the veins?

Answer 6

Decreases

Question 7

Between which two types of vessels is the decrease in pressure the greatest?

Answer 7

Arteries and arterioles
Moving into these resistance vessels the area increases dramatically as the diameter of the vessels decreases, this increase in area means that pressure decreases dramatically too

Question 8

What is the systemic filling pressure?

Answer 8

The pressure of blood exiting the circulatory system - created by the arterioles and pushes blood into the veins

Question 9

What is the pressure drop through the arteries?

Answer 9

95 to 90 mmHg

Question 10

What is the pressure drop through the arterioles?

Answer 10

90 to 40mmHg

Question 11

What is the pressure drop through the veins?

Answer 11

20 to 5 mmHg

Question 12

What is the pressure in the pulmonary circulation in comparison the to the pressure in the systemic circulation?

Answer 12

1/5th of systemic

Question 13

What is the main determinant of blood velocity?

Answer 13

Total cross-sectional area - higher it is the lower the velocity is

Fastest in aorta and slowest in capillaries

Question 14

Why do external influences affect flow in veins?

Answer 14

They are distensible and collapsible

Question 15

Is the pressure in the veins high or low?

Answer 15

Low

Question 16

Does gravity affect the driving pressure from arteries to veins?

Answer 16

No

Question 17

What does gravity cause in the veins of the legs and why?

Answer 17

Venous distension - Gravity causes increase in pressure in lower limbs and as the veins cannot cape with increased pressure, the expand and absorb the velocity of the blood

Question 18

How does the distension in the veins on the legs affect the mean arterial pressure?

Answer 18

Decrease in venous return -> EDV -> decrease preload-> decrease SV -> decrease CO -> decrease MAP

Question 19

What is orthostatic (postural) hypotension?

Answer 19

Decrease in BP when standing due to gravity

Question 20

What can jugular (venous) collapse in the neck be used to estimate?

Answer 20

Central venous pressure

Question 21

What sound is heart when cuff pressure is just less than systolic pressue?

Answer 21

Tapping - blood flow through for short time

Question 22

What sound is heard when cuff pressure is between diastolic and systolic pressure?

Answer 22

Thumping - blood flows through for longer time

Question 23

What sound is heard when cuff pressure is the same as diastolic pressure?

Answer 23

Muffled

Question 24

What sounds id heard when cuff pressure is above systolic or below diastolic pressure?

Answer 24

Nothing - flow is laminar

Question 25

What occurs during the ejection phase?

Answer 25

Ventricle muscle contracts and pushes blood through the aortic valve, making the elastic walls of the aorta swell and absorb energy

Question 26

What occurs during the relaxation phase?

Answer 26

Ventricles are filling with blood, the aortic valves are shut and the elastic energy is released from the walls of the aorta, changing the pressure

Question 27

How does SV affect the pressure wave?

Answer 27

Affects rising phase - pushing more blood into the aorta would increase the pressure

Question 28

How does the velocity of ejection affect the pressure wave?

Answer 28

If blood is pushed out fast, the elastic walls don’t have time to absorb so much energy, increasing pressure

Faster rising phase and higher peak systole

Question 29

How does the elasticity of the arteries affect the pressure wave?

Answer 29

If arteries are not elastic then the pressure will rise higher during systole and have less energy to release during the diastolic phase so the pressure will further fall

Effects rising and falling phase

Question 30

How does total peripheral resistance affect the pressure wave?

Answer 30

Affects the falling phase - if the arteries are constricted, resistance is increased, and blood flows much slower which means that pressure fall much slower during diastole

Question 31

What drives blood back to the heart?

Answer 31

The pressure difference between veins and atrium - the veins must have a higher pressure

Question 32

Describe the skeletal pump

Answer 32

Some veins travel through muscle and are squeezed during muscle contraction - valves prevent back flow so blood is pushed to heart

Static contraction of muscle does not act as a pump

Question 33

Describe the respiratory pump

Answer 33

Pressure in thorax decreases during inspiration, which also affects the vessel, and the decrease draws blood to the heart

Question 34

What is the venomotor tone?

Answer 34

The state of contraction of the smooth muscle surround the venues and veins

Question 35

How does the venomotor tone affect pressure?

Answer 35

Constriction increases pressure

Question 36

What 5 factors affect venous pressure and hence venous return?

Answer 36

Gravity 
Skeletal muscle pump
Respiratory pump
Venomotor tone 
Systemic filling pressure