Where do electrical impulses originate in the heart? ("Pacemaker" of the
heart) Right Ans - SA Node
Fill in the blank:
Auto-rhythmic cells in the _____ node _____________ (depolarize/repolarize). The
de/repolarized charge travels through the _________ to the ____ node. The _____
node ________ (quickens/slows) electrical conduction by 0.1 seconds, allowing
a break between atrial and ventricular contraction. The electrical charge then
continues to the __________, which then splits into the __________, which then
branch into the _____________. Right Ans - Auto-rhythmic cells in the SA node
DEPOLARIZE. The Depolarized charge travels through the INTERNODAL
TRACTS to the AV node. The AV node SLOWS electrical conduction by 0.1
seconds, allowing a break between atrial and ventricular contraction. The
electrical charge then continues to the BUNDLE OF HIS, which then splits into
the LEFT AND RIGHT BUNDLE BRANCHES, which then branch into the
PURKINJE FIBERS.
Depolarization leads to ________ (contraction/relaxation), while repolarization
leads to ___________(contraction/relaxation). Right Ans - Depolarization:
contraction, repolarization: relaxation
The SA node sets a pulse rate of: Right Ans - 60-100 bpm
The Bundle of His sets a pulse rate of: Right Ans - 40-60 bpm
The Purkinje fibers set a pulse rate of: Right Ans - 20-40 bpm
The SA node is reflected in which part of an ECG? Right Ans - P wave
The AV node slowing electrical impulses is reflected in which part of an ECG?
Right Ans - PR interval (0.1 seconds)
Why is the left bundle branch larger? Right Ans - Because the left side of
the heart is larger and requires more force/strength for contraction.
,The P wave represents what on an ECG? Right Ans - Atrial depolarization
(contraction)
The QRS complex represents what on an ECG? Right Ans - Ventricular
depolarization (contraction)
The T wave represents what on an ECG? Right Ans - Ventricular
repolarization (relaxation)
What is the term for a normal electrical conduction rhythm on an ECG?
Right Ans - Sinus Rhythm
What is sinus bradycardia? Right Ans - SA node rate is <60 BPM.
Everything is normal, just too slow.
What is sinus tachycardia? Right Ans - SA node rate is >100 BPM.
Everything is normal, just too fast
Where is the PR interval measured? What does it represent? Right Ans -
Measured from the beginning of the P wave to the beginning of the QRS
complex.
Represents the time it takes for the Atrium to depolarize, send signal to AV
node, AV node to delay signal, then for the signal to travel to the purkinje
fibers. (Atrium + AV node + delay + purkinje fibers)
Where is the PR segment measured? What does it represent? Right Ans -
*think of it as a SEGMENT of the PR interval
Measured from the end of the P wave to the beginning to the QRS complex
(should be a flat/isometric line).
Represents the time it takes the signal to travel through the AV node, pause,
then travel to the purkinje fibers (AV node + delay + purkinje fibers).
*this should make sense- the p wave measures atrial depolarization; the PR
segment does not include the p wave in its measurement, so atrial
depolarization is not included in this like it is in the PR interval*
, Where is the QRS complex measured? What does it represent? Right Ans -
Measured from the beginning of the Q to the end of the S.
Where is the ST segment measured? What does it represent? Right Ans -
Measured from the end of the QRS complex to the beginning of the T wave
(should a flat/isometric line).
Represents early ventricular repolarization. (if the segment is not flat, this
indicates the issue is likely caused by something wrong with the ventricles)
Where is the QT interval measured? What does it represent? Right Ans -
Measured from the beginning of the QRS complex to the end of the T wave.
Represents the time it takes for the ventricles to fully contract and fully relax.
What is the normal time for a P wave? QRS complex? Right Ans - P wave
should be no more than 5 small blocks (0.12-0.2 seconds)
QRS complex should be no more than 3 small blocks (0.04-0.12 seconds)
U waves are an abnormal finding that are usually caused by an imbalance in
what? Right Ans - electrolytes
If a QT interval is long, what will the patients HR look like? What if the QT
interval is short? Right Ans - Long QT interval= slow HR, Short QT interval=
high HR.
Why: if the ventricles are taking longer to contract and relax, the heart won't
be producing as many beats as it would if it were contracting and relaxing
quickly.
Prolonged QT interval may lead to ______________, a potentially lethal ventricular
tachycardia. Right Ans - torsades de points
Which class of medications commonly interfere with QT intervals? Right
Ans - antipsychotics
A standard ECG consists of how many leads? Right Ans - 12 leads
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