Cardiovascular system

Question 1

what is the purpose of dual circulation

Answer 1

pulmonary circulation: oxygenation of blood

systemic circulation:
- sends oxygenated blood to organs (systemic arterial system)
- collects deoxygenated blood from organs (systemic venous system)

Question 2

what is the path of systemic circulation

Answer 2

oxygenated blood: pulmonary vein > left atrium > left ventricle > aorta > systemic arteries > capillaries (organs)

deoxygenated blood: IVC/SVC > right atrium > right ventricle > pulmonary artery

Question 3

what is the path of pulmonary circulation

Answer 3

pulmonary artery (deoxygenated) > capillaries (lungs) > pulmonary vein (oxygenated)

Question 4

what are the principles of dual circulation

Answer 4

separates pulmonary and systemic circulation

separates arterial and venous circulation > communicate via capillary network

Question 5

what is arterial septal defect

Answer 5

abnormal opening between left and right atria > mixing of oxygenated and deoxygenated blood > do not get enough oxygen

Question 6

what type of blood do arteries/veins carry

Answer 6

any arteries coming off aorta: oxygenated

pulmonary artery: deoxygenated, pulmonary vein: oxygenated

systemic artery: oxygenated, systemic vein: deoxygenated

Question 7

which direction does different arteries/veins carry blood to

Answer 7

all arteries carry blood away from heart

pulmonary and systemic artery: away from heart

pulmonary and systemic vein: towards heart

Question 8

what are the 3 layers of the heart

Answer 8

epicardium (most outer layer)

myocardium (muscle)

endocardium (most inner layer)

pericardium is a sac that surrounds the membrane and shares the same layer as epicardium

Question 9

what are the mechanical events of a cardiac cycle

Answer 9

1. ventricular systole (contraction)
2. isovolumetric ventricular contraction
3. ventricular diastole (relaxation)
4. isovolumetric ventricular relaxation

Question 10

what is preload and afterload

Answer 10

preload: initial stretching of cardiac muscle cells prior to contraction

after load: the force or load against which the heart has to contrast to eject blood

Question 11

what is frank starling law

Answer 11

stroke volume of heart increases in response to increase in the volume of blood in the ventricle BEFORE contraction (end diastolic volume)

Question 12

what happens in pressure stress, eg high blood pressure

Answer 12

concentric hypertrophy occurs: increase in wall stress > walls thicken inwards into ventricle > LV cavity decreases > radius decrease + walls thicker > normalise wall stress

Question 13

what happens in volume stress, eg mitral valve not closing properly

Answer 13

eccentric hypertrophy: LV cavity increases > pressure increase since volume and pressure are related > walls thicken outwards > normalise wall stress

Question 14

what happens when preload increases

Answer 14

1. pv loop shifts to the right
2. stroke volume increases
3. EDV increases
4. secondary effect: ESV and LV pressure increases

Question 15

what happens when after load increases

Answer 15

1. pv loop shifts right
2. stroke volume decreases
3. LV pressure increases
4. secondary effect: EDV and ESV increases

Question 16

what is ESPVR and EDPVR

Answer 16

ESPVR: measure of contractility; steeper slope > higher contractility

EDPVR: measure of LV compliance; less compliant

Question 17

what happens when contractility increases

Answer 17

1. PV loop shifts left
2. stroke volume increases
3. secondary effect: smaller EDV and ESV; increase in LV pressure

Question 18

what happens when compliance increases

Answer 18

1. PV loop shifts right
2. stroke volume increases
3. secondary effect: larger EDV and ESV; increase in LV pressure

Question 19

what are the properties of capillaries

Answer 19

thin walled, extensively branched

maximize area for diffusion

large cross sectional area > slow blood velocity and maximise time for exchange

Question 20

what are the mechanisms in the vein to counter the effects of gravity

Answer 20

1. valves to allow flow in one direction
2. venoconstriction by sympathetic nervous system
3. external compression by skeletal muscles

Question 21

what causes the heart to beat

Answer 21

cardiac impulse originate at sinoatrial node (SA node) > spreads to left and right atria during atria contraction > impulses passes from atria to atrioventricular node (AV node) > travels down the Bundle of His (left and right) > rapidly moves throughout the myocardium through Purkinje fibres > ventricular contraction

Question 22

how are electrical impulses transmitted

Answer 22

auto rhythmic cells generate electrical impulses spontaneously

delivers electrical impulse (action potential) to the gap junction > carries the excitation to neighbouring cardiac muscle (contractile cells)

Question 23

what do the difference waves in an ECG mean

Answer 23

P wave: atrial depolarisation
QRS complex: ventricular depolarisation
T wave: ventricular repolarisation

Question 23

how does autonomic nervous system modulate heart rate

Answer 23

parasympathetic NS slows down heart rate by delaying closure of K+ channels > hyperpolarize

sympathetic NS increase heart rate by increasing influx of Na+