NURS 401
NURS 401 Exam 3 Questions and
Answers Graded A+ 2026
Where do electrical impulses originate in the heart? ("Pacemaker" of the heart)
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 _____________.
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).
Depolarization: contraction, repolarization: relaxation
The SA node sets a pulse rate of:
60-100 bpm
The Bundle of His sets a pulse rate of:
40-60 bpm
The Purkinje fibers set a pulse rate of:
20-40 bpm
NURS 401
,NURS 401
The SA node is reflected in which part of an ECG?
P wave
The AV node slowing electrical impulses is reflected in which part of an ECG?
PR interval (0.1 seconds)
Why is the left bundle branch larger?
Because the left side of the heart is larger and requires more force/strength for
contraction.
The P wave represents what on an ECG?
Atrial depolarization (contraction)
The QRS complex represents what on an ECG?
Ventricular depolarization (contraction)
The T wave represents what on an ECG?
Ventricular repolarization (relaxation)
What is the term for a normal electrical conduction rhythm on an ECG?
Sinus Rhythm
What is sinus bradycardia?
SA node rate is <60 BPM. Everything is normal, just too slow.
What is sinus tachycardia?
SA node rate is >100 BPM. Everything is normal, just too fast
Where is the PR interval measured? What does it represent?
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?
NURS 401
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*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?
Measured from the beginning of the Q to the end of the S.
Represents ventricular depolarization (contraction).
Where is the ST segment measured? What does it represent?
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?
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?
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?
electrolytes
NURS 401
NURS 401 Exam 3 Questions and
Answers Graded A+ 2026
Where do electrical impulses originate in the heart? ("Pacemaker" of the heart)
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 _____________.
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).
Depolarization: contraction, repolarization: relaxation
The SA node sets a pulse rate of:
60-100 bpm
The Bundle of His sets a pulse rate of:
40-60 bpm
The Purkinje fibers set a pulse rate of:
20-40 bpm
NURS 401
,NURS 401
The SA node is reflected in which part of an ECG?
P wave
The AV node slowing electrical impulses is reflected in which part of an ECG?
PR interval (0.1 seconds)
Why is the left bundle branch larger?
Because the left side of the heart is larger and requires more force/strength for
contraction.
The P wave represents what on an ECG?
Atrial depolarization (contraction)
The QRS complex represents what on an ECG?
Ventricular depolarization (contraction)
The T wave represents what on an ECG?
Ventricular repolarization (relaxation)
What is the term for a normal electrical conduction rhythm on an ECG?
Sinus Rhythm
What is sinus bradycardia?
SA node rate is <60 BPM. Everything is normal, just too slow.
What is sinus tachycardia?
SA node rate is >100 BPM. Everything is normal, just too fast
Where is the PR interval measured? What does it represent?
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?
NURS 401
, NURS 401
*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?
Measured from the beginning of the Q to the end of the S.
Represents ventricular depolarization (contraction).
Where is the ST segment measured? What does it represent?
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?
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?
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?
electrolytes
NURS 401
