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be230cLecture8

be230cLecture8 - BENG 230C Cardiovascular Physiology...

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4/25/13’ 1’ BENG’230C’Cardiovascular’Physiology’ Lecture’8’ Development’of’the’Heart’–’2’ Cardiac’Conduc±on’System Mark’Mercola,’PhD’ Professor’of’Bioengineering,’UCSD’ Professor’and’Director,’Muscle’Development’ and’Regenera±on’Program,’Sanford-Burnham’ Medical’Research’Ins±tute’ Lecture’Objec±ves’ Understand’basic’func±on’of’the’cardiac’ conduc±on’system’and’its’components’ Understand’sympathe±c’and’parasympathe±c’ eFects’on’the’heart’ Understand’the’developmental’origin’of’ cardiac’conduc±ng’cells’ Cardiac’Conduc±ng’System’ 1. SAN’²res’ 2. Propagates’quickly’ to’LA’via’ Bachman³s’bundle’ 3. Propagates’slowly’ across’RA’and’LA’ 4. Delay’in’AVN’(~0.1’ sec)’ 5. Propaga±on’to’ ventricles’via’AVN’ to’Bundle’of’His’ 6. Ventricle’ propaga±on’via’R’ and’L’bundle’ branches’and’into’ Purkinjee’²bers’ Bachman’s bundle
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4/25/13’ 2’ SA’Node’Pacemaker’ Pacemaker’channels’ acGvate’when’membrane’ hyperpolarizes’(more’ negaGve’than’-35mV).’ + influx’causes’slow’ depolarizaGon’ Ca 2+’ channels’open’at’ -40mV.’Low’density’of’the’L- type’Ca 2+’ channels’makes’ for’gradual’upstroke’ Ca 2+’ channel’inacGvaGon’ AcGvaGon’of’voltage-gated’ K + ’channels’causes’ repolarizaGon;’K + ’channels’ inacGvated’upon’ repolarizaGon’ Electrophysiological heterogeneity of the sinoatrial node (SAN). Park D S , and Fishman G I Circulation 2011;123:904-915 Copyright © American Heart Association AV’Node’Delay’ Shallow’phase’4’ (slow’depolarizing)’ Shallow’phase’0’ (upstroke);’decreases’ conducGon’velocity’ ~0.1’sec’delay’
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4/25/13’ 3’ Atrioventricular’Bundle’ A.K.A.’ l Bundle’of’His z ’ ’ From’the’AV’node,’ impulses’travel’through’ to’the’right’and’le±’ bundle’branches’ These’branches’extend’ to’the’right’and’le±’sides’ of’the’septum’and’ bo²om’of’the’heart.’ Purkinje’Fibers’ The’le±’and’right’bundle’ branchs’fork’repeatedly’to’ form’the’ Purkinje’³bers ’that’ transmit’the’impulses’to’ working’cardiomyocytes’ The’bundle’of’His,’bundle’ branches’and’Purkinje’³bers’ transmit’impulses’quickly’to’ coordinate’L’and’R’ ventricular’contracGon’ Intercellular’Impulse’PropagaGon’ Intercalated’discs:’gap’juncGons’and’ desmosomes.’´ap’juncGons’permit’ Ca 2+’ and’Na + ’transfer’between’cells.’ Desmosomes’provide’structural’ integrity.’ During’wave’propagaGon,’Na + ’and’ Ca 2+’ entering’a’cardiomyocyte’raise’
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