Cardiovascular system Flashcards
what is the purpose of dual circulation
pulmonary circulation: oxygenation of blood
systemic circulation:
- sends oxygenated blood to organs (systemic arterial system)
- collects deoxygenated blood from organs (systemic venous system)
what is the path of systemic circulation
oxygenated blood: pulmonary vein > left atrium > left ventricle > aorta > systemic arteries > capillaries (organs)
deoxygenated blood: IVC/SVC > right atrium > right ventricle > pulmonary artery
what is the path of pulmonary circulation
pulmonary artery (deoxygenated) > capillaries (lungs) > pulmonary vein (oxygenated)
what are the principles of dual circulation
separates pulmonary and systemic circulation
separates arterial and venous circulation > communicate via capillary network
what is arterial septal defect
abnormal opening between left and right atria > mixing of oxygenated and deoxygenated blood > do not get enough oxygen
what type of blood do arteries/veins carry
any arteries coming off aorta: oxygenated
pulmonary artery: deoxygenated, pulmonary vein: oxygenated
systemic artery: oxygenated, systemic vein: deoxygenated
which direction does different arteries/veins carry blood to
all arteries carry blood away from heart
pulmonary and systemic artery: away from heart
pulmonary and systemic vein: towards heart
what are the 3 layers of the heart
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
what are the mechanical events of a cardiac cycle
- ventricular systole (contraction)
- isovolumetric ventricular contraction
- ventricular diastole (relaxation)
- isovolumetric ventricular relaxation
what is preload and afterload
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
what is frank starling law
stroke volume of heart increases in response to increase in the volume of blood in the ventricle BEFORE contraction (end diastolic volume)
what happens in pressure stress, eg high blood pressure
concentric hypertrophy occurs: increase in wall stress > walls thicken inwards into ventricle > LV cavity decreases > radius decrease + walls thicker > normalise wall stress
what happens in volume stress, eg mitral valve not closing properly
eccentric hypertrophy: LV cavity increases > pressure increase since volume and pressure are related > walls thicken outwards > normalise wall stress
what happens when preload increases
- pv loop shifts to the right
- stroke volume increases
- EDV increases
- secondary effect: ESV and LV pressure increases
what happens when after load increases
- pv loop shifts right
- stroke volume decreases
- LV pressure increases
- secondary effect: EDV and ESV increases
what is ESPVR and EDPVR
ESPVR: measure of contractility; steeper slope > higher contractility
EDPVR: measure of LV compliance; less compliant
what happens when contractility increases
- PV loop shifts left
- stroke volume increases
- secondary effect: smaller EDV and ESV; increase in LV pressure
what happens when compliance increases
- PV loop shifts right
- stroke volume increases
- secondary effect: larger EDV and ESV; increase in LV pressure
what are the properties of capillaries
thin walled, extensively branched
maximize area for diffusion
large cross sectional area > slow blood velocity and maximise time for exchange
what are the mechanisms in the vein to counter the effects of gravity
- valves to allow flow in one direction
- venoconstriction by sympathetic nervous system
- external compression by skeletal muscles
what causes the heart to beat
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
how are electrical impulses transmitted
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)
what do the difference waves in an ECG mean
P wave: atrial depolarisation
QRS complex: ventricular depolarisation
T wave: ventricular repolarisation
how does autonomic nervous system modulate heart rate
parasympathetic NS slows down heart rate by delaying closure of K+ channels > hyperpolarize
sympathetic NS increase heart rate by increasing influx of Na+
