Cardiac Conduction & ECG Genesis Flashcards
(47 cards)
can specialized conduction cells contract and relax
no - can only generate action potentials
what happens if the SA and AV nodes fail
the bundles of His and Purkinje fibers have SLOW pacemaking ability
can generate 20-40 BPM
do cardiomyoctes have pacemaking ability
no - can only conduct current based on RMP and sodium channels
is conduction velocity the same across regions of the heart
no
SA node: slow - maintains rhythm
internodal: fast conduction
AV node: slow - allows adequate atrial filling before conducting signal to the ventricles
His bundle/purkinje - fast conduction for efficient contraction
where is the SA node located
junction where cranial vena cava enters right atrium
SA node conduction
spontaneous
FAST phase 4 to depolarization rate
what does ANS innervation of the SA node control
heart rate
how does the AP get conducted throughout the atrium
internodal tracts spread signal to:
1. left atrial myocytes
2. AV node
are atrial myocyte action potentials strong or weak
weak and short
function of the AV node
“gatekeeper”
controls and slows conduction to ventricles to maximize atrial filling
ONLY site that conducts atrial –> ventricular signaling
what structures can penetrate the fibrous skeleton of the heart
bundle of His & AV node
what does ANS innervation of the AV node control
conduction velocity
how does the AP get conducted throughout the ventricles
AV node –> His bundle –> L & R bundle branches –> Purkinje fibers –> ventricular myocytes –> epicardium and septum –> apex to base
are ventricular myocyte APs strong or weak
strong and long
left vs right bundle branches
L: 2 fascicles –> branch extensively
R: trabeculae septomarginalis (moderator band) spreads signal to the R ventricular wall
electrocardiogram (ECG)
graphic representation of summed electrical activity of the heart using electrodes on the body surface
what does an ECG measure
heart rate, rhythm, and conduction of electrical activity
chronotropy and dromotropy
chronotropy
initiating APs
affects HEART RATE
dromotropy
conducting APs
affects CONDUCTION VELOCITY
what does an ECG not measure
cardiac function
inotropy and lusitropy
inotropy
contractility of the muscle
lusitropy
relaxation of the muscle
what does the size and shape of the ECG waveform depend on
- direction of the current
- amount of tissue the current travels through
- speed (conduction velocity)
current direction
the direction that the current spreads throughout the myocardium in relation to the + and - pole of the leads
