1) Introduction to the Cardiovascular System

Question 1

Why do we need a Cardiovascular System (CVS)?

Answer 1

1) Temperature regulation
2) Pump blood through lungs and carry oxygen
3) Transport nutrients to muscles and organs
4) Circulates hormones and immune mediators
5) Connection to the lymphatic system
6) Human reproduction

Question 2

What is passive diffusion?

Answer 2

• The random, undirected movement of molecules

Question 3

What is the relationship between time needed to diffuse and distance?

Answer 3

• Time needed is proportional to the square of the distance:

- t α d2

Question 4

Is diffusion appropriate for transport throughout the body?

Answer 4

• No. Although diffusion is fast in µm, it is very time consuming over distances above 1 mm.
• Thus it is inappropriate for transport throughout the body.

Question 5

Describe the flow of oxygenated blood in the CVS from the lungs to the body tissues

Answer 5

• Oxygenated blood then travels, from the lungs, down the pulmonary vein into the heart via the left atrium.
• It is then pumped through the left ventricle and travels out of the heart via the aorta.
• The blood makes its way to the body through systemic arteries where it travels to capillary beds in all body tissues
• Gas exchange once again occurs in these capillary beds but this time oxygen is unloaded and carbon dioxide is loaded
• The blood is now deoxygenated

Question 6

Describe the flow of deoxygenated blood in the CVS from the body tissues to the lungs

Answer 6

• The deoxygenated blood travels up the systemic arteries back to the heart via the (superior and inferior) vena cavae.
• It is pumped into the right atrium and pumped out of the heart by the right ventricle.
• It travels up the pulmonary arteries and into the lungs.
• In the lungs the blood flows through capillary beds where gas exchange occurs. Here carbon dioxide is unloaded and oxygen is loaded
• The blood is now oxygenated

Question 7

What causes blood flow?

Answer 7

• Output of blood at high pressure causes pressure difference in blood vessels
• This pressure difference drives blood flow

Question 8

What does systole and diastole mean?

Answer 8

• Systole = contraction
• Diastole = relaxation
• Blood pressure format is normally: Systolic/ Diastolic

(For example: 120/80 mmHg means a systolic pressure of 120 and diastolic pressure of 80)

Question 9

What is the equation for cardiac output?

Answer 9

• Cardiac output = heart rate x stroke volume

- CO = HR x SV

Question 10

What is the equation for maximum heart rate?

Answer 10

220 - age = Maximum heart rate

Question 11

What is critical for correct bodily function?

Answer 11

• Blood flow

- Blood pressure

Question 12

How do we control blood flow?

Answer 12

• Controlling the resistance of the vessels

Question 13

What is the relationship of blood flow with:

i) Pressure across blood vessel
ii) Resistance of blood vessel

Answer 13

i) Blood flow is proportional to pressure across blood vessel
ii) Blood flow is inversely proportional to resistance of blood vessel

Question 14

What is the equation for blood flow?

Answer 14

• Blood flow = (Pa - Pv)/Resistance

Pa (artery): arterial pressure
Pv (vein): venous pressure

(Venous pressure varies with location and posture)

Question 15

What is the role of high pressure and low pressure in the CVS?

Answer 15

• High pressure used to pump blood around the body

- Low pressure allows gas exchange to occur

Question 16

What are the four main functional groups of blood vessels and state their functions?

Answer 16

• Arterioles (resistance vessels): Controls arterial BP and regulates local blood flow
• Arteries (elastic vessels): Accommodate stroke volume and convert ejection into continuous flow
• Venules and veins (capacitance vessels): Controls filling pressure of the heart and provides a reservoir of blood
• Capillaries (exchange vessel): Nutrient delivery to cell tissues, water and lymph formation and removal of metabolic waste

Question 17

Why does cardiac output and blood flow need to be controlled?

Answer 17

• Myocardium (muscular tissue of the heart) and brain are relatively under perfused.
• This creates clinical problems such as strokes and MI (myocardial infarction/ heart attack).

Question 18

How do arterioles control arterial BP

Answer 18

• Determining Total Peripheral Resistance (TRP).

TRP is the amount of force exerted on circulating blood by the vasculature/ blood vessels

Question 19

Arrange the CVS in order from highest pressure to lowest pressure

Answer 19

• Heart (highest)
• Aorta
• Arteries
• Arterioles
• Capillaries
• Venules
• Veins
• Vena cava (lowest)

(From the heart to the arterioles we find fluctuating pressure. The top of the fluctuations are the systolic pressure and the bottom of the fluctuations are the diastolic pressure. From the capillaries onward we find a flat line that continues to decrease in pressure)

Question 20

What causes capillaries to have a large cross-sectional area?

Answer 20

• They are made up of millions of small vessels giving a very large cross-sectional area

Question 21

What is the equation for blood velocity?

Answer 21

Blood velocity = Blood flow/ Total cross sectional area

Question 22

Where do we find the largest total-cross sectional area?

Answer 22

• In the capillaries.

- This allows for a slow mean velocity which allows nutrient and gas exchange to take place

Question 23

What are the three divisions of blood vessel walls?

Answer 23

• Tunica adventitia (outer layer) consisting of external elastic membrane
• Tunica media (middle layer) consisting of smooth muscle
• Tunica intima (inner layer) consisting of endothelium (and internal elastic membrane in arteries only)

Question 24

What causes vasoconstriction?

Answer 24

-Sympathetic nerves in the tunica adventitia release noradrenaline which stimulate α1 receptors leading to vasoconstriction.

Question 25

What causes vasodilation?

Answer 25

• The endothelium release nitric oxide which relaxes vessels leading to vasodilation