cardiac conduction -physiology Flashcards
what does the SA node contain
pacemaker cells
What is the path that the electrical current follows in the heart?
SA->AV-> bundle of His-> bundle branches-> Purkinje fibres
what is the resting potential for SA nodal cells
they do not have a stable resting potential
why is there a delay in conduction of AV node
conduction velocity slows down to allow time for ventricular filling
what is plan B if the SA node doesn’t work?
other part of the atria take over
what is plan C if the SA node doesn’t work
the AV node will take over
what is plan D if the SA node doesn’t word
the His-purkinge fibres take over
what do the left bundle branches split into ?
anterior + posterior fascicles
why is there a PR interval?
-because the AV node has a slow action potential creating a delay
-PR interval represents the activation of the AV node and bundle of His
Where is the PR interval measured from?
-from the beginning of the P wave to the start of the QRS complex (beginning of the Q)
How long is a normal PR interval?
120- 200 ms
0.12- 0.2 s
3-5 small squares
What PR interval would suggest heart block?
PR interval longer than:
5 small boxes
0.2 s
200 ms
