Lecture 12: Venous Blood Flow and the Heart

Question 1

Where is most of the blood in our body found?

Answer 1

Systemic veins

Question 2

Why can’t we store extra blood in our pulmonary circuit?

Answer 2

It is too small

Question 3

Why can’t we store extra blood in our systemic arteries?

Answer 3

It would raise our blood pressure

Question 4

Why can’t we store extra blood in our capillaries?

Answer 4

They are too small

Question 5

How are veins able to store more blood in them?

Answer 5

They have a higher compliance

Question 6

What allows veins to have a higher compliance?

Answer 6

They have a thin tunica media which allows room for compliance

Question 7

What doesn’t allow arteries to have a higher compliance?

Answer 7

Thick tunica media forming a more rigid structure

Question 8

What is compliance?

Answer 8

The extent to which a vessel allows deformation in response to an applied force

Question 9

What is the equation for compliance?

Answer 9

Delta V/P

Question 10

What does it mean for compliance if it takes more pressure to change the volume of a vessel?

Answer 10

The less compliant it is

Question 11

What allows arteries to maintain their shape even under low pressure?

Answer 11

A thick tunica media

Question 12

What happens to veins under low pressure?

Answer 12

They collapse as pressure conforms shape

Question 13

What does a small portion of pressure do to the volume of a vein?

Answer 13

It causes a large change in volume

Question 14

What is meant by veins having survival value?

Answer 14

They can move blood over to arteries in an emergency situation

Question 15

What is venoconstriction?

Answer 15

contraction of veins pushing blood stored there into the arteries

Question 16

What can happen as a consequence of an arterial puncture?

2

Answer 16

• Loss of arteriole blood

- Life-threatening fall in arterial pressure

Question 17

What controls venoconstriction?

Answer 17

Neural control

Question 18

What does supine mean?

Answer 18

Lying down

Question 19

What happens to venous volume whilst supine?

Answer 19

It is uniform

Question 20

What happens to venous volume whilst standing up?

2

Answer 20

• Venous volume below the heart increases

- Venous volume above the heart decreases

Question 21

What is larger venous or arterial volume?

Answer 21

Venous

Question 22

What does gravity pulling blood down cause the veins to do?

Answer 22

Causes the veins to bow

Question 23

Where does venous pooling mainly occur?

Answer 23

Legs/feet

Question 24

What helps counteract venous pooling?

2

Answer 24

• Venous valves

- Tone of surrounding tissue

Question 25

What does muscle tone do?

Answer 25

Acts to stiffen the veins, making them less compliant and less prone to pooling

Question 26

What do some people prone to fainting possess?

Answer 26

Low muscle tone and excessive pooling

Question 27

What do skeletal muscle contractions do to blood?

Answer 27

Increase venous return to the heart

Question 28

What do venous valves superior to the contracting muscle do?

Answer 28

Open, allowing blood to move towards the heart

Question 29

What do venous valves inferior to the contracting muscle do?

Answer 29

They are forced closed, preventing back flow of blood to the capillaries

Question 30

What does breathing do to the intercostal muscles and intern blood?

Answer 30

Pushes intercostal muscles against veins pumping blood towards the heart

Question 31

What is Starling's law of the heart?

Answer 31

The more stretched muscles fibres are before a contraction, the stronger the contraction will be

Question 32

What does an increased venous return mean?

Answer 32

An increased stroke volume

Question 33

What does a larger stretch of cardiac muscles do to the maximum contraction of the heart?

Answer 33

Larger maximum contraction