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because its spontaneous depolarization - that propgated through the heart through the sepcialized system of cardiomyocytes is the pulse generator of the heart under normal conditions
i need in a lil easy term please
can u please explain the meaning of depolarisation as in nervous system i learn that it means inside -ve outside +ve in vessel is it like that?
one more thing i dont get here that please tell me abu specialised system is it means bundle of his, purkinjee fibres dats all??
pulse generator means SA node is pulse generator in heart which helps in contraction of auricle right. plz ans my ques
well... all heart muscle cells spontenously depolarize, even in a lab plastic dish. for a heart to work as an efficient pump it has to happen in concert. a single - synchronized cycle. the SA node - located in the outer layer of the right atrium, near the superior vena cava (i think, not positively sure) is the cell group with the highest autonomous beat (yes of depolarization, we'll get to it soon). when it "fires" - the signal spreads through the path of the leat resistance - which is the dedicated conduction fiber which is comprised of the AVN, his bundle and purkinje - like u mentioned. through this cooridanted depolariztion - the heart contracts most efficiently. let us talk some pathologies: if for some reason there is a conduction block in which the san wont "fire" the atrio ventricular node, or even the cardiac chamber itslef will depolarize, albeit at a slower - "escape" rate. the avn spontaneous rate is ~55 bpm. the left chamber is ~40. lets talk ventricualar tachycardia - in which for complicated reasons not to be discussed now - the depolarization occurs abberantly in a loop inside the the cardiac chambers - and not through the avn - what happens: we lose syncrhonized atrial contraction, but even worse - the rate of depolarization of this loop is so quick (over 200) that the heart has no time to relax - and get filled with blood (AKA - diastole) and even worse - it tires, may get ischemic and eventually we might die... more will come with specific questions
thanQ thanQ so much............. :)
SA node is called the pacemaker of the heart as it the first one to generate impulses for contraction and relaxation of heart muscle (pumping action). SA node passes the impulses (or in simple words messages) to the heart atria and also sends it to the AV node (atrioventricular node) so that the impulses reach the ventricles too. Hope u know that heart beats 72 times per minute... that is maintained by ur conducting system - SA node to begin with and then passes on to AV node and then to bundle of His and it branches, and finally to Purkinje fibres.
yes i knw and thnx to all of u