Introduction to the CVS

Question 1

Why is a cardiovascular system needed?

Answer 1

1. To pump blood through lungs; carry oxygen to tissues
2. To transport nutrients to muscle and organs/ take away metabolites
3. Form connection with lymphatic system
4. To facilitate human reproduction
5. To help with temperature regulation

Question 2

What is passive diffusion?

Answer 2

The random, undirected thermal movement of molecules.

Question 3

Why is passive diffusion not suitable for transporting blood around the body?

Answer 3

Time needed to diffuse a given distance is proportional to the square of the distance. This means it would take too long toto transport blood this way

Question 4

Why is the heart described as a double pump?

Answer 4

left side pumps oxygenated blood to the tissues while the right side pumps deoxygenated blood to the lungs

Question 5

What are the 4 chambers of the heart called?

Answer 5

Left and right atria

Left and right ventricles

Question 6

Is pressure higher within the arteries or the veins?

Answer 6

Arteries

Question 7

What is it that drives blood to flow around the body?

Answer 7

Pressure difference between the arteries and the veins

Question 8

What is cardiac output?

Answer 8

Volume of blood ejected from the heart per minute

Question 9

What organ receives the least amount of blood from the heart and why is this the case?

Answer 9

Myocardium (muscular tissue of heart) - only gets 4% of blood
This is because during systole coronary arteries “scrunch up” meaning no blood flows through them. It is only during diastole that the coronary arteries are able to have blood flow through them thus allowing them to deliver oxygenated blood to the myocardium.

Question 10

What 2 organs can be described as “under perfused”?

Answer 10

Myocardium - Consumes 10% of your oxygen but only gets 4% of blood
Brain - Consumes 18% of your oxygen but only gets 13% of your blood

Question 11

Why can these organs receive less blood relative to the amount of oxygen they need?

Answer 11

Because they have specialised ways of extracting more oxygen from less blood relative to other organs

Question 12

what does the fact that these organs are under perfused mean for them?

Answer 12

Makes them both vulnerable to cardiovascular disease which can cause them problems e.g. angina, MI, stroke

Question 13

What is the equation for cardiac output?

Answer 13

Cardiac output = heart rate x stroke volume

Question 14

What are the 3 ways of controlling cardiac output?

Answer 14

1. Filling pressure (Starling’s law)
2. Sympathetic and parasympathetic autonomic nerves
3. Chemical factors and hormones (Adrenaline)

Question 15

What is blood flow proportional to?

Answer 15

proportional to pressure across blood vessel

Question 16

What is blood flow inversely proportional to?

Answer 16

inversely proportional to resistance of blood vessel

Question 17

What is the equation for blood flow?

Answer 17

Blood flow = Arterial pressure - Venous pressure / resistance

Question 18

What is meant by systemic circulation?

Answer 18

Circulation of oxygenated blood away from the heart to the body and then circulation of deoxygenated blood back to the heart (right atrium)

Question 19

What is meant by pulmonary circulation?

Answer 19

Circulation of deoxygenated blood to the lungs and circulation of oxygenated blood back to the heart (left atrium)

Question 20

What is the equation for the total cross-sectional area of circulation?

Answer 20

Number of vessels x cross-sectional area of each individual vessel

Question 21

Why does the total cross-sectional area increase as you go from the aorta to the capillaries?

Answer 21

Because the circulatory system increasingly branches meaning that the increase in the no. of vessels outweighs the decrease in vessel size

Question 22

Why is the total-cross sectional area within the capillaries so high?

Answer 22

Increases the rate of gaseous/nutrient exchange

Question 23

What is the equation for blood velocity?

Answer 23

Blood velocity = Blood flow/ total-cross sectional area

Question 24

What does the low blood velocity within the capillaries allow?

Answer 24

Allows for sufficient time for gaseous/nutrient exchange

Question 25

What are the 3 main layers within the arterial and venous walls?

Answer 25

1. Tunica intima - sheet of flattened endothelial cells
2. Tunica Media - smooth muscle cells arranged in helical patterns (found in matrix of collagen and elastin fibres).
3. Tunica adventitia - Connective tissue sheath

Question 26

What is the mechanism that causes the arterial wall to contract?

Answer 26

Sympathetic nerves in Tunica adventitia releasing Noradrenaline causing stimulation of α1 adrenoreceptors leading to vasoconstriction (contraction)

Question 27

What is the mechanism that causes the arterial wall to relax?

Answer 27

Endothelium releasing nitric oxide which relaxes the vessels leading to vasodilation (relaxation)

Question 28

What are the differences between the arterial and venous walls?

Answer 28

Veins have much less smooth muscle

They also have less sympathetic innervation than the arterial walls do

Question 29

What are the 4 main functional groups of blood vessels?

Answer 29

Elastic fibres - arteries
Resistance vessels - arterioles
Exchange vessels - capillaries
Capacitance vessels - veins and venules