CVS: introduction

Question 1

Why do we need a CVS?

Answer 1

1. Pump blood through lungs and carry oxygen
2. Regulate the body temperature
3. Transports nutrients to the 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

Passive diffusion is the random undirected thermal movement of molecules

Question 3

Explain how distance affects the rate of diffusion

Answer 3

The time needed to diffuse given distance is proportional to the square of the distance
T ∝ D^2
Where:
T= time
D= distance
Diffusion is mostly efficient is micrometers (um) but NOT in >1mm; therefore it is not suitable for transport throughout the body

Question 4

What causes blood to flow in the body?

Answer 4

The PRESSURE DIFFERENCE between the aorta (HIGH) and the large veins (LOW)
Output of blood at high pressure creates a pressure difference with distant blood vessels

Question 5

What is meant by systole?

Answer 5

Systole = contraction

Question 6

What is meant by diastole?

Answer 6

Diastole = relaxation

die=rest=relax

Question 7

What is meant by cardiac output?

Answer 7

Volume of blood ejected from the heart per minute

usually 5litres/min

Question 8

Where does cardiac output go?

Answer 8

1. Liver
   
   2. GI
   3. Muscle
   4. Brain
   5. Myocardium
   6. Kidney

and other places

Question 9

describe why blood flow to the brain and myocardium are important

Answer 9

The brain and myocardium are under perfused; meaning a small drop in perfusion could mean risk of:
→ Angina
→ MI (myocardial infarction)
and Stroke

Question 10

Name the 3 things that control cardiac output

Answer 10

1. Filling pressure (sterling’s law)
2. Sympathetic and parasympathetic autonomic nerves
3. Chemical factors and hormones (eg- adrenaline)

Question 11

What is the equation used to calculate cardiac output?

Answer 11

Cardiac output = heart rate x stroke volume

Units: litres/min

Question 12

Why are blood flow and blood pressure important?

Answer 12

Blood flow and blood pressure are critical for correct bodily functioning. This is because they are linked in the proper distribution of blood.

Question 13

What is the equation for calculating blood flow?

Answer 13

(Pa - Pv)
Blood flow = ————–
Resistance

Pa= arterial pressure 
Pv= venule pressure 

· This means the higher resistance = less blood flow
· Blood flow is proportional to pressure across blood vessel
- Blood flow is inversely proportional to resistance of blood vessel

Question 14

Give an example of where blood flow slows down and explain why this happens

Answer 14

Blood flow slows down in capillaries (pulmonary circulation) to allow for gaseous/nutrient exchange to occur

Question 15

Why is the blood flow slower in the capillaries?

Answer 15

The velocity of blood is much slower in the capillaries to allow for gaseous/nutrient exchange to occur

Question 16

describe the cross sectional area of capillaries compared to aorta and describe the impact this has on the blood velocity

Answer 16

Capillaries are made up of LOADS of small vessels = large cross-sectional area
Aorta is ONE large vessels = low cross-sectional area

Smaller cross sectional area = blood speed up
Larger cross sectional area = blood slows down

Question 17

describe the type of circulation used to supply the body organs

Answer 17

Most organs are supplied with blood in parallel dual circulation

Question 18

what is systemic circulation

Answer 18

Systemic: oxygenated blood from the lungs enter the left side of the heart via the pulmonary veins. This blood can then travel round the body, delivering oxygen to tissues and organs

Question 19

what is pulmonary circulation

Answer 19

Pulmonary: deoxygenated blood travels from the right atrium to the lungs via the pulmonary arteries

Question 20

What are the differences between the venous and arterial walls?

Answer 20

Arteries have a THICKER elastic wall to maintain blood pressure
Veins has THINNER elastic walls

Question 21

Describe the role of the arteries and veins in the flow of blood

Answer 21

Arteries: have a high pressure that ensures blood flows in one direction

Veins: have valves that ensure blood flows in one direction

Question 22

what is the endothelium in a blood vessel and what is it’s purpose

Answer 22

Endothelium- inner lining of the artery

Produces NO which relaxes the vessel

Question 23

what is the tunica media in a blood vessel and what is its purpose

Answer 23

Tunica media- smooth muscle walls (circular layers)
Contraction = narrow
In the tunica media, stimulation of alpha-1 adrenoreceptors by NA = vasoconstriction

Question 24

What happens if the body wants to increase blood flow?

Answer 24

Endothelium NO overpowers the ANS = vasodilation = more blood flow

Question 25

What happens if the body wants to decrease blood flow?

Answer 25

ANS overpowers NO, and releases NA to stimulate the A-1 adrenoreceptors = vasoconstriction = less blood flow

Question 26

what is the main function of the arteries

Answer 26

Elastic vessels: ARTERIES

Large arties that accommodate stroke volume AND convert intermittent ejection into continuous flow

Question 27

what is the main function of the arterioles

Answer 27

Resistance vessels: ARTERIOLES

Control arterial blood pressure and regulates local blood flow

Question 28

what is the main function of the capillaries

Answer 28

Exchange vessels: CAPILLARIES
Nutrient delivery to cells and tissues for water and lymph formation
Removal of metabolic waste

Question 29

what is the main function of the venues and veins

Answer 29

Capacitance vessels: VENULES + VEINS
Control the filling pressure and provide a reservoir of blood, so the veins can constrict and send blood to the heart if needed