heart as a pump

Question 1

why does systemic circulation require high pressure?

Answer 1

efficient distribution to the whole body

Question 2

why are lungs perfused at a lower pressure?

Answer 2

pulmonary vascular resistance is lower than systemic vascular resistance

Question 3

describe the structures of the systemic arteries and pulmonary arteries

Answer 3

systemic - moderate size and thick muscular walls

pulmonary - large diameter thin elastic walls

Question 4

what does starling’s law state?

Answer 4

increased preload increases end diastolic volume

Question 5

explain starling’s law

Answer 5

more blood to the ventricles –> expand to a greater diameter –> contract more strongly –> higher EDV –> higher SV –> higher CO

Question 6

what is preload and what determines it?

Answer 6

preload is the degree of stretching of the ventricles during diastole

determined by the volume of blood brought to the heart by the veins

Question 7

what is the stroke volume of a normal healthy adult male?

Answer 7

70ml

Question 8

what is residual volume?

Answer 8

the blood that is always left in the ventricles at the end of systole

Question 9

how is the stroke volume calculated?

Answer 9

finding the difference between end diastolic volume and end systolic volume

Question 10

how does preload affect the myocardial muscle fibre length?

Answer 10

increases the fibre length

Question 11

what limits starling’s law?

Answer 11

if ventricles stretch beyond aa certain point then the mechanism doesn’t work

Question 12

how does heart failure occur?

Answer 12

ventricles stretch too far
ventricles enlarge with no increase in wall thickness
contracts more weakly
larger EDV produces smaller stroke volume

Question 13

explain the mechanism underlying starling’s law

Answer 13

actin and myosin filaments have excess overlap at rest

stretching increases the overlap and causes an increased force of contraction

Question 14

define afterload

Answer 14

the effective flow impedance (resistance) of the aorta and the large arteries

Question 15

what determines afterload

Answer 15

elasticity of the tissues and diameter of blood vessels

Question 16

what is compliance?

Answer 16

reciprocal of impedance

Question 17

how does a higher compliance affect after load and the work o the heart?

Answer 17

high compliance = lower after load = less work for the heart

Question 18

explain how after load increases in old people

Answer 18

elasticity of arteries is lost

elastic tissue replaced by collagen

Question 19

what effect does smoking have on afterload?

Answer 19

increases afterload

Question 20

explain how a greater afterload leads to a larger residual volume

Answer 20

greater afterload
longer contraction of ventricles before aortic valve opens
smaller stroke volume
larger residual volume

Question 21

what is inotropy?

Answer 21

force of contraction of ventricular muscle

Question 22

how does an increase in inotropy affect stroke volume?

Answer 22

increases stroke volume

Question 23

name factors which increase contractility

Answer 23

increased blood calcium levels
beta adrenergic agonists (like adrenaline)
drugs which stimulate calcium entry into myocardium
cardiac glycosides
insulin
glucagon

Question 24

what do chordae tendineae do?

Answer 24

keep heart valves in position when closed

Question 25

what muscle is first to contract in ventricular systole?

Answer 25

papillary muscle

Question 26

what does papillary muscle do?

Answer 26

pull on the chordae tendineae and pull valves closed

Question 27

what is atrial fibrillation?

Answer 27

irregular and abnormally fast heart rate caused by electrical impulses being fired off from all over the atria

Question 28

what are symptoms of atrial fibrilation?

Answer 28

dizziness and breathlessness during exercise

Question 29

how does atrial fibrillation look on an ECG?

Answer 29

lack of P waves

Question 30

what causes the 1st and 2nd heart sound?

Answer 30

1st - when AV valves close

2nd - closing of semilunar valves

Question 31

what causes splitting of the first heart sound?

Answer 31

asynchronous closing of the tricuspid and mitral valve

Question 32

at what point in the cardiac cycle is the 3rd heart sound heard?

Answer 32

1/3 of the way through diastole

Question 33

what causes the third heart sound?

Answer 33

turbulent filling of blood in early diastole

Question 34

what people is S3 heard in?

Answer 34

children and young adults

adults with heart disease

Question 35

when is S4 heard and what causes it?

Answer 35

immediately before the 1st heart sound

turbulent blood flow in ventricles during late filling

Question 36

what is S4 a sign of?

Answer 36

decreased ventricular compliance

Question 37

what are gallops?

Answer 37

sounds associated with diastolic filling

Question 38

what is a phonocardiogram?

Answer 38

shows heart sounds that have been recorded and amplified

Question 39

what is the jugular venous pressure?

Answer 39

the faint pulse caused by the back pressure into the jugular vein when the right atrium contracts

Question 40

what are the peaks in the jugular venous pulse and what causes them?

Answer 40

a wave - atrial contraction before tricuspid closes

c wave - pressure rise in the atrium when tricuspid valve closes and bulges into atrium

v - when ventricles reach peak of contraction and tricuspid valve bulges again

Question 41

what 3 factors mediate venous return into the heart? explain each

Answer 41

one way valves in the vein - prevent back flow

muscular pump - contract to propel blood up into the heart

thoracic-abdominal pump - pressure changes push blood into the heart. during inspiration, pressure decreases and blood is pulled into the inferior IV

Question 42

why is restoring venous drainage less important than restoring arterial supply in organ/limb damage?

Answer 42

veins have many anastomoses for alternative pathways of blood