Electrical Properties of the Heart Flashcards
the heart is electrically connected by
gap junctions
the heart is physically connected by
desmosomes
Gap junctions and desmosomes together make the
intercalated disc
excitation contraction coupling is the process whereby an
action potential triggers a myocyte to contract (and then subsequently relax)
Cardiac muscle has a …… action potential
long (about 250msec)
Cardiac muscles has a long refractory period so it cannot exhibit
tetanic contraction
Ca2+ entry from outside the cell can regulate
contraction
calcium release does not saturate the troponin 0 so the regulation of Ca2+ release can be used in
varying the strength of contraction
Pacemaker potential
the slow, positive increase in cells membrane potential that occurs at the end of the AP til the start of the new AP
(what causes it to reach threshold potential and fire an AP)
Ca2+ channel blockers
decrease the force of contraction
Cardiac glycosides
increase the force of contraction
hyperkalaemia
fibrillation and heart block
hypokalaemia
fibrillation and heart block
hypercalcaemia
increased HR and force of contraction
hypocalcemia
decreased HR and force of contraction
Sinoatrial node is the
pacemaker
AV node is the
delay box
Bundle of his
transmits electrical impulses from AV node to ventricles
Lots of small extracellular electrical potentials evoked by many cells depolarising can
summate to create large electrical waves
P wave corresponds to
atrial depolarisation
QRS complex corresponds to
ventricular depolarisation
T wave corresponds to
ventricular repolarisation
