Pressure and Flow in Arteries and Veins

Question 1

What Korotkoff sounds are heard when decreasing the pressure of a sphygmomanomater and auscultating with a stethoscope on the arteries?

Answer 1

• Dotted line represents pressure
• Tapping sound tells you systolic pressure
• Muffled sound tells you diastolic pressure

Question 2

What are elastic arteries able to do during systole?

Answer 2

Store some of the energy in their elastic fibres

Question 3

What 4 things effect the pressure wave?

Answer 3

• Stroke volume
• Velocity of injection
• Elasticity of arteries
• Total peripheral resistance

Question 4

What is the systemic filling pressure?

Answer 4

Pressure left after a full systemic blood travel that allows the blood to get back to the ventricles

Question 5

What happens to pressure throughout the vascular tree?

Answer 5

It falls

Question 6

How much does pressure drop through the arterioles?

Answer 6

Tiny drop from about 95 to 90mmHg

Question 7

What is the change in pressure in the arterioles like?

Answer 7

90 to 40 mmHg

Question 8

Why is it good that pressure is low when the blood reaches the capillaries?

Answer 8

They are very thin walled and would rupture

Question 9

What is the pressure difference through the veins?

Answer 9

From 20 to 5mmHg

This is the systemic filling pressure

Question 10

What fraction of systemic blood pressure is pulmonary?

Answer 10

1/5th

Question 11

What is velocity of blood related to?

Answer 11

• Total cross section
• Fastest in aorta and vena cava
• Slowest in capillaries

Question 12

What would happen to blood flow if pressure didn’t fall throughout the vascular tree?

Answer 12

Blood would reverse

Question 13

Study the vascular tree diagram

Answer 13

Question 14

Why do external influences affect flow through veins?

Answer 14

• Pressure is low
• Vessels are distensible and collapsible

Question 15

What effect does gravity have on pressure and flow in veins?

Answer 15

• Causes venous distention in legs
• Reduces EDV, preload, SV, CO and MAP

Question 16

What conditions can be caused by gravity?

Answer 16

• Can cause orthostatic (postural) hypotension
• Can cause venous collapse in neck

Question 17

What is the difference in venous pressure from the head to the thorax while standing?

Answer 17

Roughly - 40mmHg difference

Question 18

What is the venous pressure change from the thorax to the foot while standing?

Answer 18

About +100mmHg

Question 19

What can the height of jugular collapse allow to be estimated?

Answer 19

Central venous pressure (the higher the collapse the higher the pressure

Question 20

What is the skeletal muscle pump?

Answer 20

Skeletal muscles in the leg that increase venous return

Question 22

When do these skeletal muscle pumps fail?

Answer 22

During static exercise

Question 23

How does the respiratory pump aid venous return?

Answer 23

Respiratory inspiration increases thoracic pressure and venous return increases due to a decrease in right atrial pressure

Question 24

What is the venomotor tone?

Answer 24

State of contraction of smooth muscle surrounding venules and veins

Question 25

What does the venomotor tone do?

Answer 25

Decides the capacitance of the vessels, can contract to increase venous return