8.2 Cardiovascular System

Question 1

What is pulmonary circulation?

Answer 1

Portion of CVS carrying deoxygenated blood away from heart, to lungs and returns oxygenated blood back to the heart

Question 2

What is systemic circulation?

Answer 2

Part of CVS carrying oxygenated blood to the body (not inc. lungs), and returns deoxygenated blood back to the heart

Question 3

Describe the circulation of blood in the heart

Answer 3

1) deoxygenated blood through IVC and SVC to right atrium
2) through tricuspid valve into right ventricle
3) through pulmonary valve and pulmonary artery to lung
4) oxygenated blood returns through pulmonary vein to left atrium
5) through mitral valve into left ventricle
6) through aortic valve and aorta the rest of the body
7) deoxygenated blood returns through IVC and SVC

Question 4

What is the function of the heart? (3)

Answer 4

1) Circulates and transports nutrients, oxygen, carbon dioxide, hormones, blood cells to and from the cells of the body
2) fights disease
3) homeostasis - temperature, pH

Question 5

How many litres of blood do we have?

Answer 5

5L

Question 6

Of the 5L of blood we have, percentages where?

Answer 6

65% (3.25L) in veins
20% (1L) in heart and lungs
10% (0.5L) in peripheral arteries
5% (0.25L) in capillaries - note greatest surface area though - 600m2!

Question 7

Why is the left ventricle more muscular than the right side?

Answer 7

Because left ventricle pumps to the whole body whereas the right side pumps to the lungs only

Question 8

Of the 5L of blood, how much is RBC and how much is plasma?

Answer 8

2L RBC, 3L blood plasma

Question 9

What is coronary bridging?

Answer 9

1) systole - causes coronary arteries to compress

2) diastole - reverses

Question 10

Describe the electrical system of the heart. (4)

Answer 10

1) Sinoatrial Node (pacemaker)
- automatically creates own action potential, depolarises
2) Bachmanns bundle
- depolarisation from SA node
- both atriums contract together
3) Internodal tracts
- carry impulse from SA node to AV node
4) Atrioventricular node
- creates a delay (0.13s) when contracting after atriums so ventricles can fill up with blood
5) Bundle of his - transmits impulse from AV node to purkinje fibres
6) Purkinje fibres - ventricles contract together and pumps blood to pulmonary artery and aorta

Question 11

What is the more scientific term for shimmering? Describe this and how it could be treated.

Answer 11

Ventricular fibrillation
When no communication between atriums and ventricles
Defibrillator to treat and make electrical signals cause contraction normally again

Question 12

CVS is a closed system. Starting from the heart, what vessels leave, go round to the body and tissues and then return?

Answer 12

Heart - Large elastic arteries - Medium muscular arteries - Arterioles (resistance vessels) - Metarterioles (resistance vessels) - capillaries - post capillary venules - venules - medium veins - large veins - heart

Question 13

Wall structure of medium muscular artery?

Answer 13

Tunica intima - endothelium, thick internal elastic fibres
Tunica media - 40 layers of smooth muscle cells! Connected by gap junctions for coordinated contraction, prominent external elastic lamina
Tunica Adventitia - thin layer of fibroelastic CT, vasa vasorum not prominent, lymphatic vessels and sympathetic nerve fibres

Question 14

How are messages conveyed to medium muscular arteries from the ANS?

Answer 14

Neurotransmitter (NA) released at the nerve endings diffuses to external elastic lamina
Into external tunica media where it depolarises some smooth muscle cells
Depolarisation propagated to all cells of tunica media via gap junctions

Question 15

What is the function of meta arterioles and an important structural feature?

Answer 15

Supply blood to capillaries

Precapillary sphincters

Question 16

What are precapillary sphincters?

Answer 16

1) Formed from meta arterioles
2) controlling blood flow flowing into capillary beds depending on where blood is needed most
3) can dilate 60-100% resting diameter
4) can maintain 40% constriction

Question 17

What are pericytes?

Answer 17

Covering outer surface of capillary and can differentiate into muscle cells and fibroblasts - important for wound healing

Question 18

What are end arteries? Give examples.

Answer 18

Terminal artery supplying all/most blood to a body part without collateral circulation.

Coronary, splenic, cerebral, renal arteries
Absolute end - central artery to retina

Question 19

What is collateral circulation?

Answer 19

Alternate circulation (branches form) around blocked artery/vein

Question 20

What is ischaemia?

Answer 20

1) Restriction in blood supply to tissues

2) Shortage of oxygen - hypoxia

Question 21

Post-capillary venule function

Answer 21

1) Receive blood from capillaries

2) more permeable than capillaries so fluid drains into veins here

Question 22

Most veins do not have a prominent tunica media apart from one. What is it called and why does it have a prominent tunica media?

Answer 22

Superficial vein of the leg

It has a well defined muscular wall as it resists distension caused by gravity

Question 23

Another name for veins is ____________ vessels ? And why?

Answer 23

1) Capacitance
2) veins have thin non-elastic walls that can stretch a great deal without giving pressure back (Recoil) like elastic does
3) Because ability to increase volume of blood it holds without large increase in pressure
4) greater amount of elastic tissue, smaller compliance

Question 24

How does venous blood get back from legs to heart?

Answer 24

Calf muscle contracts and acts as a pump
Sympathetic nerve activity stimulates smooth muscle contraction
Respiratory activity -
Valves

Question 25

Calf muscle pump failure could lead to venous hypertension, why? What could cause this?

Answer 25

Blood flow through veins inadequate so pressure exerted on walls is higher, higher bp - hypertension. Inadequate flow of blood. Could cause dizziness. Valve damage, standing still for too long, standing up too fast

Question 26

What is a vertical gradient of venous pressure?

Answer 26

Highest pressure by ankles, lower nearer heart when human standing. When lying down, pressure lower near ankles

Question 27

What are the arteries supplying to the heart called?

Answer 27

Right coronary artery, posterior descending artery, left anterior descending artery.

Question 28

What happens to the cells of left ventricle hypertrophy? What are the causes of this?

Answer 28

The left ventricle is a lot thicker than usual Could be caused by increased pressure on the heart I.e. Blood clot, aortic valve stenosis (narrowing of aortic valve so LV has to pump harder to body), systemic hypertension (high BP in systemic arteries - vessels that carry blood heart => body)

Question 29

What is happening physiologically in heart failure? Symptoms and causes?

Answer 29

Often Left ventricle failure - "floppy" left ventricle So increased volume in LV although reduced stroke volume ``` Dysponea (shortness of breath), fatigue, weakness Oedema Ascites (swelling of your abdomen) Rapid/irregular heartbeat Lack of appetite and nausea ``` ``` Coronary heart disease (coronary arteries that supply o2 to heart could become narrowed by gradual build up of fatty material) High BP Faulty heart valves Damage to heart Congenital ```

Question 30

What is stroke volume?

Answer 30

Amount of blood ejected by LV in one contraction

Question 31

What is frank starlings law?

Answer 31

Stroke volume of heart increases in response to an increase in the volume of blood filling the heart I.e. Larger vol of blood in ventricles, more expansion of heart walls, increases force of contraction (like pulling a rubber band further and letting go)

Question 32

If the heart is pumped too much, the myosin can come out of the adjacent actin filaments which can cause irreversible damage. What protein is released indicating this?

Answer 32

Brain Natriuretic peptide - BNP Released from ventricles Levels increased markedly in left ventricle dysfunction and HF Important clinical marker!

Question 33

Why does left ventricular failure lead to pulmonary oedema?

Answer 33

The heart is not able to pump blood to the body efficiently The amount of blood in pulmonary artery - lungs - pulmonary vein increases Pressure increases forcing fluid out into air spaces of alveoli in lungs Reduces normal oxygen movement through lungs - shortness of breath

Question 34

What could be measured in the blood and urine respectively if there was 'dead' muscle in the leg?

Answer 34

Creatine kinase and myoglobinuria (released from skeletal muscle, oxygen carrier myoglobin secreted in urine)