heart physiology Flashcards
structure of cardiac muscle cells
striated, branching with internal connections through intercalated discs
mechanism and events of contraction
autorhythmic contraction
organ coordinated contraction
time of contraction with a single stimulus is much longer with cardiac cells
autorhythmic contraction
many cardiac cells are self excitable
how does the heart have coordinated contraction
ion transfer through discs alow cardiac muscle cells to stimulat contracion of adjoining cells
membranes are linked
steps to contraction
na+ entry begins depolarization
depolarization triggers ca2+ channel to open in the membrane, the influx stimulates more ca2+ release from the sarcoplasmic reticulum
rpolarization
what does the medication verapamil do
calcium channel blocker slows ca2+ entry, decrease heart contraction duration and easing stress on damaged cardiac cells
how do the cells maintain autorhythmic cells
localized, modififed cardiac cells leak na slowl and depolarize themselves on a regular basis
how is sinus rhythm obtained
SA node depolarized at regular intervals as Na leaks into these cells triggering depolarization
how many beats is sinus rhythm
~75 bpm
where are the autorhythmic cells located that set the basic rhtyhm
sinoatrial node atrioventricular node atrioventricular bunder right and left bundle branches ventricular walls (purkinje fibers
atrioventricular node
AV node also autorhythmic but slower at 50
when is av node utilized
to stimulate heart beat in absence of sa node signal
what does signal hit after AV node
the bundle of His
right and left bundle branches
purkinje fibers
when do bundle branches depolarize
depolarize at 30 bpm if no signal
when is a pacemake necessary
if arrythmias are present
