Intro to The Cardiovascular System

Question 1

What functions does the CVS aid / carry out in the body?

Answer 1

• Pumps blood through lungs
• Carries O₂, removes CO₂ and waste materials
• Transports nutrients to muscles & organs
• Circulates hormones and immune mediators
• Human reproduction
• Temperature regulation (vasodilation and
  vasoconstriction)

Question 2

What is passive diffusion?

Answer 2

The random, undirected thermal movements of molecules

Question 3

What is the relationship between time and distance of diffusion?

Answer 3

The time taken to diffuse a given distance, is proportional to the square of the distance
t ∝ d²

Question 4

Why is diffusion not used for whole body transport?

Answer 4

Diffusion is most effective in distances in µm but is very time consuming for distances > 1 mm
- inappropriate for whole body transport

Question 5

Give examples of times taken for diffusion to occur in different parts of the body

Answer 5

Synapse - 0.1 µm takes 0.005 ms
Capillary –> cell - 10 µm takes 50 ms
Cartilage - 1 mm takes 8 minutes
Left ventricle wall - 1 cm takes 13 hours

Question 6

What is myocardium?

Answer 6

The muscular tissue of the heart

Question 7

What causes a pressure difference in the heart?

Answer 7

Output of blood at high pressure creates a pressure difference in distant blood vessels

Question 8

What is the average pressure maintained in the aorta and large veins respectively?

Answer 8

Aorta > 100 mm Hg

Large veins 5 - 10 mm Hg

Question 9

What is meant by systole?

Answer 9

Contraction

Question 10

What does diastole mean?

Answer 10

Relaxation

Question 11

Outline the equation to calculate Cardiac output

Answer 11

CO = HR x SV

Question 12

Describe quantitatively how the CO differs at rest and during exercise

Answer 12

at rest: 70 bpm x 70 ml = 5 litres / min

during exercise: 18 bpm x 120 ml = 20 litres / min

Question 13

What are the average blood pressures of systemic and pulmonary circulation?

Answer 13

Systemic circulation - 120/80 mm Hg

Pulmonary circulation - 25/15 mm Hg

Question 14

What is cardiac output?

Answer 14

The volume of blood ejected from the heart per minute, typically around 5 litres / min

Question 15

What is the role of high blood pressure?

Answer 15

High pressure enables blood to be pumped around the whole body

Question 16

Typically, how is the cardiac output distributed throughout the body at rest?

Answer 16

25% Liver & GI tract 
20% Muscle 
20% Kidney 
18% Other
13% Brain
4% Myocardium

Question 17

Describe the structure and function of elastic vessels

Answer 17

Arteries
Large arteries accommodate Stroke volume
Convert intermittent ejection to into continuous flow

Question 18

How is blood flow and blood pressure controlled?

Answer 18

Controlling the resistance of vessels gives some control of blood flow
High resistance = decreased flow

Blood Flow = (Pa - Pv) / resistance

Question 19

What are exchange vessels?

Answer 19

Capillaries

Provide nutrient delivery to cell tissue, water, lymph formation and removal of metabolites and waste

Question 20

What is the function of low blood pressure?

Answer 20

Allows time for exchange of gases and nutrients in capillaries

Question 21

What factors affect Cardiac Output?

Answer 21

Starling’s law (filling pressure)
Sympathetic + Parasympathetic nervous systems
Chemical factors + hormones

Question 22

What are the 4 main functional groups of blood vessels?

Answer 22

• Elastic vessels
• Exchange vessels
• Resistance vessels
• Capacitance vessels

Question 23

Describe the structure of the capillary network

Answer 23

Capillaries are made up of millions of small vessels, giving a large cross-sectional area = slower velocity

Question 24

What is the consequence of under perfused myocardium and brain?

Answer 24

This creates potential clinical problems
- angina
- MI
- strokes
triggered by relatively moderate falls in perfusion
CO needs to be carefully controlled

Question 25

Why is pressure in the aorta higher than in capillaries?

Answer 25

The aorta is just one vessel so has a very low cross-sectional area

Question 26

What is the role of arterioles?

Answer 26

Arterioles are resistance vessels, controlling arterial blood pressure by determining total peripheral resistance (TPR)

Question 27

Describe the percentage oxygen consumption by the body during rest

Answer 27

30% Liver, GI tract 
20% Muscle 
18% Brain 
10% Kidneys 
10% Myocardium 
12% other

Question 28

Why is it important to control blood flow?

Answer 28

Blood flow and blood pressure control is significant for correct bodily functioning

Question 29

What is meant by series blood flow in dual circulation?

Answer 29

Same blood supply between organs
lower perfusion pressures
medically significant if first organ is under perfused

Question 30

Describe the arterial vessel wall structure

Answer 30

Thick tunica adventitia (external elastic membrane)
Thick tunica media (smooth muscle)
Contains internal elastic membrane
Tunica intima and endothelium

Question 31

Give the equation used to calculate blood velocity (m/s)

Answer 31

Blood velocity (m/s) = Blood flow (cm³/s) / SA (cm²)

Question 32

What is parallel circulation?

Answer 32

When the cardiac output is split up, safeguarding the O₂ supply in organs
Most organs are supplied in parallel

Question 33

Describe the function of resistance vessels

Answer 33

Arterioles

Control arterial blood pressure and regulate local blood flow

Question 34

Describe the percentage distribution of the body’s blood volume

Answer 34

5% capillaries
10% arteries 
10% heart 
10% lungs 
24% large veins 
24% small veins & venules

Question 35

What is the role of veins & venules?

Answer 35

Systemic veins & venules act as reservoirs for blood, holding up to 65% of the body’s total blood volume

Question 36

What are capacitance vessels?

Answer 36

Venules & veins

They control filling pressure and provide reservoir of blood