L6 The Heart Flashcards
what does the AV node delay allow
allows auricular systole to finish before ventricular systole
why does contraction of vent start at botton
otherwise blood pushed into vent away from exit (toothpaste)
define automaticity
ability to generate a heart beat
o Nodes + purkinje = intrinsic rhythmicity which generates a pacemaker potential
define ectopic beat
a beat generated outside the normal pacemaker
define chronotrpoc
agents that alter HR
what are pos chronotpric
increase HR- (Adrenaline and Noradrenaline act on b-adrenergic receptors)
what are neg chronotropic
decrease HR- (Acetylcholine acts on M-cholinergic (muscarinic))
why doesn’t heart follow SA node beat of 90min
slowed by para
explain heart block
ailure AV node (heart block) = p wave (atria) beating at unusual rate (2 p waves in row)
explain ECG of vent fib
chaotic
explain ectopic beat on ECG
- 2nd QRS before T wave, inverted
o No t wave= no ejection of blood as didn’t have time to fill through repolarisation
What are the heart valves
- 2 bw atria & ventricles= atrioventricular (AV) valves
* 2 bw ventricles & arteries= semilunar (SL) valves
function of H valves
• The heart valves prevent back flow of blood
explain ECG
- P wave: atrial depolarisation + atrial systole
- QRS: ventricles depolarise + contract, isovolumetric contraction
- T wave: ventricular repolarisation +
Explain heart sounds in cardiac cycle
- Close of AV valves = S1 at peak of QRS
- Closure of SL= S2 at end of t wave
