Pathophysiology of Dysrhythmias + Classifcations of Antiarrhythmics 2 Flashcards
What does the cardiac muscle require to allow actin to bind to myosin?
Ca2+
Describe what happens in cardiomyocyte contraction
Ca2+ enters through L-type channel
Ca2+-induced release occurs = intracellular Ca2+ rises
Ca2+ interacts with troponin-C
Myosin binding site on actin freed
Actin moves over myosin = myocyte contraction
Describe how cardiomyocyte contraction is ended
Intracellular Ca2+ reabsorbed into SR
Removed by Na+/Ca2+ exchanger
Ca2+ dissociates from troponin-C
What is required to unbind myosin from actin?
ATP
Describe what happens in Ca2+-induced Ca2+ release
Initial influx through L-type
Sarcolemma T-tubules bring L-type close to ryanodine receptors
Ca2+ activates ryanodine receptors on SR
= release from Ca2+ reserve
How is contraction ended in Ca2+-induced Ca2+ release?
Intracellular Ca2+ returns to SR
Via Ca2+ transport ATPase
Describe propagation of AP
Depolarisation in SAN
Impulse travels to AVN
Delayed before propagating into ventricles
Depolarisation spreads through Bundle of His
Endocardium depolarised through Purkinje fibre
Depolarisation happens from endo (outside) to epicardium (inside)
Synchronous contraction of heart
What are cardiac dysrhythmias?
Disruption of contraction control
What are the different types of supraventricular arrhythmias?
Sinus tachycardia
Atrial tachycardia
Paroxysmal atrial tachycardia
Atrial flutter
Atrial fibrillation
AV blocks
What is sinus tachycardia?
Rate of 100-180 bpm occurs during exercise or other conditions
What is atrial tachycardia?
Series of 3 or more consecutive atrial premature beats
What is paroxysmal atrial tachycardia?
Tachycardia which begins + ends acutely
What is atrial flutter?
250-350 bpm
What is atrial fibrillation?
Uncoordinated atrial depolarisations
What are AV blocks?
Block within AV node or Bundle of His
