UCLA EKG EXAM SCRIPT 2025/2026 QUESTIONS WITH
ANSWERS GRADED A+
✔✔What do the myocardial cells do? - ✔✔The contractile machinery of the heart
• When a myocardial cell is depolarized,
calcium is released within the cell,
causing the cell to contract.
• Myocardial cells transmit an electrical current,
but far less efficient.
✔✔What are the SA, AV, and purkinje rates? - ✔✔•SA node (• 60-100 bpm)
•AV node (• 40-60 bpm)
•Purkinje fibers (• 20-40 bpm)
✔✔What are the normal electrolyte levels for sodium, K, CA, ionized CA, Mg? - ✔✔Na:
135-146 mEq/L
• K: 3.6-5.3 mEq/L
• Ca: 8.5-10.3 mg/dL
• Ionized Ca 1.09-1.29 mmol/L (Corrected:1.10 mmol/L)
• Mg: 1.4 - 1.9mEq/L
✔✔Purpose of EKG - ✔✔Monitors electrical currents created by impulses in the
heart through electrodes attached to the skin
• Shows the sequence of electrical events
• Doesn't show the heart's mechanical activity or
pumping ability
✔✔Difference between electrodes and leads when measuring EKG - ✔✔Electrodes
• Detect electrical currents from the
heart that radiate to the skin
• Are placed at different locations to
obtain a total picture of the heart's
electrical activity
Leads
• Provide a view of the heart's electrical
activity between two points, or poles
• Consist of one positive pole and one
negative pole
• Produce either positive or negative
deflections on the ECG
✔✔What is the placement of precordial electrodes? - ✔✔• V1 Right sternal boarder and
4 th intercostal space
• V2 Left sternal boarder and 4 th intercostal space
, • V3 Between V2 and V4
• V4 Midclavicular line and 5 th intercostal space
• V5 Between V4 and V6
• V6 Between Midaxillary line and 5th intercostal space
✔✔How many small squares are there in between the heavy dark lines in an EKG? -
✔✔• Smallest divisions are one millimeter squares
• The EKG paper runs at constant speed of 25mm/sec.
• There are 5 small squares between the heavy dark
lines.
✔✔What is the time of each small box in an EKG square? - ✔✔• Each small box = 0.04
seconds
• 5 small boxes = 0.2 seconds
• 5 large boxes = 1 second
• 300 large boxes = 1500 small boxes = 60 seconds (1 minute)
✔✔What does the P wave tell you? - ✔✔• Represents atrial depolarization—conduction
of an electrical impulse from sinoatrial (SA) node through atria • Characteristics: •
Location: precedes the QRS • Configuration: usually rounded and upright; no peaks or
notches
✔✔What does the PR interval represent? - ✔✔AV node slows conduction, causing
pause at 0.12 - 0.2 seconds.
• The physiologic delay is essential to allow the atria to finish contracting before the
ventricles begin to contract
Measured from the beginning of the P wave to the beginning of the QRS complex
✔✔What are components of the QRS complex? - ✔✔Represents ventricular
depolarization
• Duration: 0.04-0.12 seconds (clinically 0.06-0.10) Characteristics:
• Q wave: Negative deflection before the R wave
• R wave: First positive deflection in the complex
• S wave: Negative deflection after the R wave
✔✔What does the T wave tell you? - ✔✔Represents ventricular repolarization
• A much slower process than ventricular depolarization • Should be in the same
direction as R waves.
✔✔What does the U wave tell you? - ✔✔Small low amplitude wave that follows T wave
• May be indicative of hypokalemia
✔✔What does the ST segment represent? - ✔✔Measures the time from the end of
ventricular depolarization to the start of ventricular repolarization • Normally falls on the
isoelectric line.
ANSWERS GRADED A+
✔✔What do the myocardial cells do? - ✔✔The contractile machinery of the heart
• When a myocardial cell is depolarized,
calcium is released within the cell,
causing the cell to contract.
• Myocardial cells transmit an electrical current,
but far less efficient.
✔✔What are the SA, AV, and purkinje rates? - ✔✔•SA node (• 60-100 bpm)
•AV node (• 40-60 bpm)
•Purkinje fibers (• 20-40 bpm)
✔✔What are the normal electrolyte levels for sodium, K, CA, ionized CA, Mg? - ✔✔Na:
135-146 mEq/L
• K: 3.6-5.3 mEq/L
• Ca: 8.5-10.3 mg/dL
• Ionized Ca 1.09-1.29 mmol/L (Corrected:1.10 mmol/L)
• Mg: 1.4 - 1.9mEq/L
✔✔Purpose of EKG - ✔✔Monitors electrical currents created by impulses in the
heart through electrodes attached to the skin
• Shows the sequence of electrical events
• Doesn't show the heart's mechanical activity or
pumping ability
✔✔Difference between electrodes and leads when measuring EKG - ✔✔Electrodes
• Detect electrical currents from the
heart that radiate to the skin
• Are placed at different locations to
obtain a total picture of the heart's
electrical activity
Leads
• Provide a view of the heart's electrical
activity between two points, or poles
• Consist of one positive pole and one
negative pole
• Produce either positive or negative
deflections on the ECG
✔✔What is the placement of precordial electrodes? - ✔✔• V1 Right sternal boarder and
4 th intercostal space
• V2 Left sternal boarder and 4 th intercostal space
, • V3 Between V2 and V4
• V4 Midclavicular line and 5 th intercostal space
• V5 Between V4 and V6
• V6 Between Midaxillary line and 5th intercostal space
✔✔How many small squares are there in between the heavy dark lines in an EKG? -
✔✔• Smallest divisions are one millimeter squares
• The EKG paper runs at constant speed of 25mm/sec.
• There are 5 small squares between the heavy dark
lines.
✔✔What is the time of each small box in an EKG square? - ✔✔• Each small box = 0.04
seconds
• 5 small boxes = 0.2 seconds
• 5 large boxes = 1 second
• 300 large boxes = 1500 small boxes = 60 seconds (1 minute)
✔✔What does the P wave tell you? - ✔✔• Represents atrial depolarization—conduction
of an electrical impulse from sinoatrial (SA) node through atria • Characteristics: •
Location: precedes the QRS • Configuration: usually rounded and upright; no peaks or
notches
✔✔What does the PR interval represent? - ✔✔AV node slows conduction, causing
pause at 0.12 - 0.2 seconds.
• The physiologic delay is essential to allow the atria to finish contracting before the
ventricles begin to contract
Measured from the beginning of the P wave to the beginning of the QRS complex
✔✔What are components of the QRS complex? - ✔✔Represents ventricular
depolarization
• Duration: 0.04-0.12 seconds (clinically 0.06-0.10) Characteristics:
• Q wave: Negative deflection before the R wave
• R wave: First positive deflection in the complex
• S wave: Negative deflection after the R wave
✔✔What does the T wave tell you? - ✔✔Represents ventricular repolarization
• A much slower process than ventricular depolarization • Should be in the same
direction as R waves.
✔✔What does the U wave tell you? - ✔✔Small low amplitude wave that follows T wave
• May be indicative of hypokalemia
✔✔What does the ST segment represent? - ✔✔Measures the time from the end of
ventricular depolarization to the start of ventricular repolarization • Normally falls on the
isoelectric line.
