cardiac physiology Flashcards
atrial extrasystoles
arises from the atrial muscle.
the abnormal impulse resets the SA node and therefore it is sollwed by a normal period of diastole
ventricular and nodal extrasystoles
arise from the ventricular muslce and AV node and bundle respectivel
this extrasystole does not reset the SA node and is therefore follwed by the normal impulse produced by the SA node which cannot be transmitted ot the ventricle due to them being in ARP. therefore they are followed by a compensatory pause due to a longer diastole.
atrial flutter
the atria beat a high rate therefore their pumping action is diminished.
due to the long refractory period of the AV node, not all these impulses travel to the ventricle(heart block)
atrial fibrillation
atria beat at an extreemly high rate and the individyual atrial fibres beat differently and the pumping action of the atria is completely lost. there will be irregular ventricular beating as well as the treshold is not alwasy reached.
ventricular flutter
ventricles beat at a high rate, cardiac output is diminshed and may lead yo faintoing
ventricular fibrillation
ventricles beat at a very high rate, myocardial fibres beat asynchronously , ventricular pumping action is completely lost usually leads to death
conditions that give rise to circus movement
- decrease in the velocity of the impulse (blockage in purkinje fibres, ischaemia of the muscle, high blood potassium )
- length of the pathway (longer) (dilated heart)
- shortening of the refractory period (adrenaline or electric AC shock)
3 factors that control stroke volume
preload - degreee of mycoardial distension
contractility (independant of preload)
afterload (force to push blood out - resistance to arteries
factors affecting the preload
venous returna dn filling time
factors affecting contractility
autonomic innervation and hormones
factors affecting the afterload
vasodilation vasoconstriction
factors affecting venous return
gravity, blood volume, sympathetic vasoconctrcion tone, respiratory pump, mean systemic filling pressure, skeletal pump, cardiac suction
main 2 factors controlling heart rate
autonomic inervation and hormones
factors affecting blood pressure
cardiac output
resistance
blood volume
3 things used for the rapid regulation of blood pressure
- baroreceptors: stretch receptors, when stimulated they inhibity the vasoconstrictor centre and excite the vagal centre. vasodilation leads to decrease in HR and blood pressure
- chemoreceptors: 2 carotid bodies and several aortic. fall in bp leads to decrease on O2 and pH and ncrease in CO2. thsi stimulates chemorecpetors and vasoconstriction centre.
- atrial and pulmonary receptors: detetc changes in blood volume
long term regulation of blood pressure
renal body fluid system
high bp results in increae in renal output of water and salts resulting in a decrease of ECF volume and tehrefore blood volume.
how does laminar flow become turbluent flow
-increase in flood
- goes over obstruction
- makes a sharp turn
- passes over rough surface
heart sounds
1- sudden closure of AV valves -systolic
2- sudden closure of aortic and pulmonary vialves- diastolic
3- vibrations in ventricular wall due to rapid filling
4 - auricular contraction and rush of blood into ventricle
between the first and second there is systol and from the second to the first there is diastole
3 types of murmurs
systolic, diastolic and continuous
systolic murmurs
occur during ventricular systole between 1st and 2nd heart sound
Organic murmurs
- narrowing or stenosis fo aortic or pulmoanry valves
- widening or regurgitation of the mitral or tricuspid valve
- congenital interventricular spetal defect
Functional murmurs: fever, anaemia exercise etc
diastolic murmurs
occur during diastole after the second heart sound
Organic murmurs
- narrowing or stenosis of the mitral or tricuspid valve
- widening or regurgitation of the aortic or pulmonary valve
continuous murmurs
occur during systolic and diastolic periods (machinery murmur)
eg due to duct between aorta and pulmonary artery at birth
