1 | Page
UCLA EKG Test Questions and Correct
Answers
Polarized Ans: At rest;
K+ inside > outside; Na+ outside > inside
The difference b/w charges in/out of cell wall is the
electron potential.
Electrical potential = -90mV (Negative inside)
Depolarization Ans: Contracting;
Na+ moves into cell rapidly → Inside loses negative
potential = Depolarization
Repolarization Ans: Return to rest;
Ions return to resting state and heart cells restore resting
polarity
Pacemaker rate: Sinoatrial (SA) node Ans: 60-100 bpm
Pacemaker rate: Atrioventricular (AV) node Ans: 40-60 bpm
Pacemaker rate: Purkinje fibers ("ventricle pacemaker")
Ans: 20-40 bpm
© 2025 All rights reserved
, 2 | Page
Conduction pathway Ans: SA node → (internodal
pathways) → AV node → (Bundle of His) → (Bundle
branches) → Purkinje fibers
Sinoatrial (SA) node Ans: Primary pacemaker*
Rate: 60-100 bpm
Depolarize the atria via internodal tracts = atrial
contraction
Atrioventricular (AV) node Ans: Subsidiary pacemaker
Rate: 40-60 bpm
Responsible for slowing down conduction from atria to
ventricles just long enough for atrial contraction to occur
Purkinje cells Ans: Subsidiary pacemaker
Rate: 20-40 bpm
EKG: Major leads Ans: V1 + Lead II
V1 + Lead II placement locations
V2-6? Ans: V1 = Right sternal border, 4th intercostal space
V2 = Left sternal border, 4th intercostal space
V4 = Midclavicular line, 5th intercostal space (PMI)
V6 = Midaxillary line, 5th intercostal space
V3 = Between V2-V4
© 2025 All rights reserved
, 3 | Page
V5 = Between V4-V6
Components of EKG Ans: 1. P wave = Atrial depolarization
(SA node)
2. Completed atrial depolarization, delayed impulse at AV
node
3. QRS = Ventricular depolarization, atrial repolarization
4. Completed ventricular depolarization
5. T wave = Ventricular repolarization
6. Repolarization complete
EKG Graph paper sizes Ans: Small box = 0.04 sec
Large box = 0.20 sec
1 vertical box = 1 mm = 1 mV
P wave Ans: Depolarization of atria
Precedes QRS
PR interval Ans: Duration: 0.12-0.2 sec
-How long it takes for atrium to contract before ventricle
contracts
-Measured from P to beginning of Q
-AV node slows conduction, causing pause
QRS complex Ans: Duration: 0.04-0.12
-Ventricular depolarization
© 2025 All rights reserved
UCLA EKG Test Questions and Correct
Answers
Polarized Ans: At rest;
K+ inside > outside; Na+ outside > inside
The difference b/w charges in/out of cell wall is the
electron potential.
Electrical potential = -90mV (Negative inside)
Depolarization Ans: Contracting;
Na+ moves into cell rapidly → Inside loses negative
potential = Depolarization
Repolarization Ans: Return to rest;
Ions return to resting state and heart cells restore resting
polarity
Pacemaker rate: Sinoatrial (SA) node Ans: 60-100 bpm
Pacemaker rate: Atrioventricular (AV) node Ans: 40-60 bpm
Pacemaker rate: Purkinje fibers ("ventricle pacemaker")
Ans: 20-40 bpm
© 2025 All rights reserved
, 2 | Page
Conduction pathway Ans: SA node → (internodal
pathways) → AV node → (Bundle of His) → (Bundle
branches) → Purkinje fibers
Sinoatrial (SA) node Ans: Primary pacemaker*
Rate: 60-100 bpm
Depolarize the atria via internodal tracts = atrial
contraction
Atrioventricular (AV) node Ans: Subsidiary pacemaker
Rate: 40-60 bpm
Responsible for slowing down conduction from atria to
ventricles just long enough for atrial contraction to occur
Purkinje cells Ans: Subsidiary pacemaker
Rate: 20-40 bpm
EKG: Major leads Ans: V1 + Lead II
V1 + Lead II placement locations
V2-6? Ans: V1 = Right sternal border, 4th intercostal space
V2 = Left sternal border, 4th intercostal space
V4 = Midclavicular line, 5th intercostal space (PMI)
V6 = Midaxillary line, 5th intercostal space
V3 = Between V2-V4
© 2025 All rights reserved
, 3 | Page
V5 = Between V4-V6
Components of EKG Ans: 1. P wave = Atrial depolarization
(SA node)
2. Completed atrial depolarization, delayed impulse at AV
node
3. QRS = Ventricular depolarization, atrial repolarization
4. Completed ventricular depolarization
5. T wave = Ventricular repolarization
6. Repolarization complete
EKG Graph paper sizes Ans: Small box = 0.04 sec
Large box = 0.20 sec
1 vertical box = 1 mm = 1 mV
P wave Ans: Depolarization of atria
Precedes QRS
PR interval Ans: Duration: 0.12-0.2 sec
-How long it takes for atrium to contract before ventricle
contracts
-Measured from P to beginning of Q
-AV node slows conduction, causing pause
QRS complex Ans: Duration: 0.04-0.12
-Ventricular depolarization
© 2025 All rights reserved
