Cardiac Physiology 2023

Question 1 of 72

Which of the following is the depolarization phase of the action potential in pacemaker cells?

Phase 3
Phase 0
Phase 1
Phase 2
Phase 4

Question 2 of 72

Which part of the cardiac cycle corresponds to the ST segment?

Atrial repolarization
Ventricular repolarization
Atrial depolarization
Ventricular depolarization
The interval between ventricular depolarization and repolarization

Question 3 of 72

What is the mean electrical axis if standard limb lead I is biphasic, and aVF is the most positive?

+70°
-120°
+120°
+30°
+90°

Question 4 of 72

Which stage of the cardiac cycle do the atrioventricular valves open?

Isovolumetric contraction
Ventricular ejection
Ventricular filling
Atrial contraction
Atrial filling

Question 5 of 72

Which of the following cardiac changes will increase stroke volume?

Increased afterload
Increased end-systolic volume
Increased preload
Decreased inotropy
Decreased cardiac contractility

Question 6 of 72

What is the beating frequency of the SA node?

40-100 bpm
40-60 bpm
60-90 bpm
30-40 bpm
60-100 bpm

Question 7 of 72

Which of the following elements of the cardiac electrical pathway are the slowest conductors?

Atrial muscle
AV node
Ventricular muscle
Bundle branches
Purkinje fibers

Question 8 of 72

Which of the following influences the corrected QT (QTc)?

Blood oxygenation
Mean arterial pressure
Respiratory rate
Blood pressure
Heart rate

Question 9 of 72

Which of the following represents the normal systolic pressure in the right ventricle?

2-6 mmHg
6-12 mmHg
70-105 mmHg
0-8 mmHg
15-25 mmHg

Question 10 of 72

Which of the following physiological conditions causes a greater atrial contraction?

An increase in premature ventricular contractions
A decrease in sympathetic nervous system stimulation
Atrial fibrillation
An increase in venous return
An increase in parasympathetic nervous system stimulation

Question 11 of 72

To which of the following muscarinic receptors on the SA node does acetylcholine bind to?

M4 receptors
M1 receptors
M3 receptors
M2 receptors
M5 receptors

Question 12 of 72

Which of the following terms is associated with the activation of the heart by the sympathetic nervous system?

Negative inotropy
Positive lusitropy
Positive dromotropy
Hypertrophy
Negative chronotropy

Question 13 of 72

A patient’s ECG shows a PR interval that is lengthened to 0.3 seconds throughout the tracing but still captures a normal QRS complex. Which of the following ECG abnormalities does this describe?

Atrial fibrillation
Mobitz type I
1st-degree AV block
3rd-degree AV block
Ventricular fibrillation

Question 14 of 72

Which of the following contributes to 2nd heart sound?

Closure of aortic and the pulmonary valves
Closure of AV valves
Contraction of ventricles
Contraction of atria
The flow of blood from atria

Question 15 of 72

Which of the following adrenergic receptors does norepinephrine bind to in order to speed up the heart?

α2 adrenergic receptors
α1 adrenergic receptors
β2 adrenergic receptors
β1 adrenergic receptors
β3 adrenergic receptors

Question 16 of 72

Which of the following conditions results in complete dissociation of atrial and ventricular activity?

Type I second-degree AV block
Atrial defibrillation
Third-degree AV block
First-degree AV block
Type 2 second-degree AV block

Question 17 of 72

Which phase of the cardiac cycle does the a-wave occur?

Phase 3-4
Phases 5-7
Phase 1-2
Phase 6-7
Phase 5-6

Question 18 of 72

Which of the following contributes to 1st heart sound during systole?

Closure of semilunar valves
Closure of AV valves
The flow of blood from atria
Contraction of ventricles
Contraction of atria

Question 19 of 72

Which of the following will most likely lead to an increase in heart rate?

Hypothyroidism
Hyperkalemia
Increase in epinephrine
Decrease in all catecholamines

Question 20 of 72

Which of the following ECG abnormalities is seen with premature ventricular complexes?

Wide QRS complex
P wave after QRS complex
Absent QRS complex
Variation in P wave contour
Irregular ventricular response

Question 21 of 72

Which of the following describes a random QRS > 0.1s seen in normal sinus rhythm?

Sinus arrhythmia
Ventricular tachycardia
Ventricular fibrillation
Premature atrial complex
Premature Ventricular Complex

Question 22 of 72

Which of the following is a primary factor that affects end-diastolic volume?

Dromotropy
Preload
Inotropy
Stroke volume
Afterload

Question 23 of 72

The conductance of which ion results in phase 2 characteristics in a ventricular myocyte action potential?

Chloride
Calcium
Potassium
Magnesium
Sodium

Question 24 of 72

Which of the following test is meant to create a record of the heart’s electrical activity at rest?

Electrocardiogram (ECG)
Echocardiography
Cardiac MRI
Exercise stress test
MUGA Scan

Question 25 of 72

Which of the following changes are seen on an ECG when transmural ischemia is present?

Absent P wave, ST-segment elevation, normal T wave
Normal P wave, ST-segment depression, inverted T wave
Normal P wave, ST-segment elevation, normal T wave
Notched P wave, Normal ST-segment, inverted T wave
Normal P wave, ST-segment elevation, absent T wave

Question 26 of 72

Which of the given formulas calculates cardiac output?

End diastolic volume × Heart rate
Stroke volume × Heart rate
End systolic volume ÷ Heart rate
End diastolic volume – Heart rate
End diastolic volume – End systolic volume

Question 27 of 72

Which of the below elements of the cardiac electrical pathway are the fastest conductors?

Atrial muscle
Ventricular muscle fibers
AV node
Purkinje fibers
Bundle branches

Question 28 of 72

Which of the following statements characterizes the ECG electrical activity between a pair of positive and negative electrodes?

If the depolarization wave travels toward a negative electrical pole you will get a positive deflection on the ECG.
A single pair of positive and negative electrodes can give multiple electrical views of the heart without repositioning the electrodes.
The ECG is not concerned with the polarity of the electrodes.
It represents the average of the many depolarization vectors “seen” in the heart taken by those electrodes.
The positive and negative electrodes can be switched without affecting the ECG.

Question 29 of 72

What occurs in both systole and diastole?

Active relaxation
Ventricular filling
Active contraction
Ventricular ejection
Ventricular ejection & active contraction

Question 30 of 72

Which of the following factors affects the velocity of myocardial contraction?

BMI of an individual.
The surface area of the valve.
Ease of valvular opening.
Available energy in the form of ATP.
Quality of blood flow.

Question 31 of 72

Which of the following is FALSE regarding the effect of sympathetic stimulation of the heart?

Decreased rate of phase 4 depolarization
Increased phosphorylation of Ca channels
Increased Na influx
Increased HCN activity
Increased cyclic adenosine monophosphate

Question 32 of 72

Which of the following corresponds to the QRS complex?

Right ventricular repolarization
Atrial depolarization
Left ventricular repolarization
Atrial repolarization
Ventricular depolarization

Question 33 of 72

Which of the following is TRUE regarding the cardiac cycle?

Systole is the contraction phase and diastole is the relaxation phase.
Diastole is the contraction phase and systole is the relaxation phase.
Systole is exclusively the contraction of the atria.
Both the contraction and relaxation phases are termed systole.
Both the contraction and relaxation phases are termed diastole.

Question 34 of 72

Which of the following effects on ventricular function happen with a decrease in inotropy?

Increases stroke volume
Decreases stroke volume
Increase dP/dt
Increase EF
Decrease preload

Question 35 of 72

Which of the following decreases the heart rate?

High T3
Hypokalemia
Noradrenaline
Low levels of thyroid hormones
Adrenaline

Question 36 of 72

Which frontal plane lead would have the greatest (tallest) r-wave if the mean electrical axis is 60°?

Lead II
Lead III
aVR
Lead I
aVL

Question 37 of 72

Which of the following stages of the cardiac cycle does the ventricular volume curve drop sharply?

Passive filling
Atrial contraction
Ejection
Isovolumic contraction
Isovolumic relaxation

Question 38 of 72

Which of the following parameters decreases ventricular preload?

Decreased venous compliance
Increased ventricular compliance
Decreased ventricular inotropy
Decreased atrial inotropy
Increased afterload

Question 39 of 72

Which of the following drug classes can increase the heart rate?

Calcium channel blockers
K channel blockers
Digoxin
Beta blockers
Adrenergic agonists

Question 40 of 72

What would the mean electrical axis be if aVR is the most biphasic, and standard limb lead III is the most positive?

-30°
+120°
0°
+60°
-150°

Question 41 of 72

Where do you measure left ventricular end-diastolic volume and left ventricular end-systolic volume, respectively?

Both can be measured in the filling phase.
Mid-filling phase and the last point of the ejection phase
Isovolumic relaxation and mid-ejection phase
The last point of the ejection phase and isovolumic relaxation
Isovolumic contraction and the last point of the ejection phase

Question 42 of 72

Which of the given parameters is related to the Frank-Starling law of the heart?

Venous pressure and ventricular compliance
Stroke volume and end-diastolic volume
Stroke volume and end-systolic volume
Heart rate and preload
Preload and afterload

Question 43 of 72

In resting conditions, which of the following channels is most likely open in a cardiac myocyte?

Calcium channels
Potassium channels
Explanation
Sodium channels
Chloride channels

Question 44 of 72

Which component of the intercalated disks that hold cardiomyocytes together allows for rapid passage of electrical impulses?

Tight junctions
Desmosomes
Anchoring junctions
Hemidesmosomes
Gap junctions

Question 45 of 72

Which electrocardiogram interval is used to calculate the heart rate?

RR interval
QRS interval
T wave interval
PR interval
ST interval

Question 46 of 72

What percentage of ventricular filling can atrial systole account for during exercise conditions?

40%
50%
30%
10%
60%

Question 47 of 72

Which of the following will decrease with a decrease in the afterload?

Stroke volume
Blood Volume
End-systolic volume
The velocity of muscle shortening
Cardiac output

Question 48 of 72

What is the primary current responsible for phase 0 of the action potential in a nodal cell?

I Ca (L)
I K
I f
I Ca (T)

Question 49 of 72

Which of the following occurs during cardiomyocyte depolarization?

Potassium and calcium move into the cell
Sodium and potassium move out of the cell
Sodium moves out of the cell
Calcium and sodium move out of the cell
Sodium and calcium move into the cell

Question 50 of 72

Which of the following is the definition of the ST segment?

End of the QRS complex to the end of the T wave
Start of the S wave to the beginning of the T wave
Start of the QRS complex to the start of the T wave
End of the S wave to the beginning of the T wave
End of the S wave to the end of the T wave

Question 51 of 72

What is the normal range of the ejection fraction?

55-60%
30-40%
15-25%
25-35%
80-90%

Question 52 of 72

Which of the following is CORRECT regarding the effect of afterload on ventricular function?

Increasing the afterload would decrease preload.
Reducing the afterload would increase end-systolic volume.
Reducing the afterload would increase the stroke volume.
Increasing the afterload would decrease the end-diastolic volume.
Decreasing the afterload would increase preload.

Question 53 of 72

Which of the following is the mechanism by which the sympathetic nervous system increases the heart rate?

Lower or more negative shift in resting membrane potential
Greater absolute amount of repolarization
Increasing rate of phase 4 depolarization
Increasing the threshold potential to a less negative value

Question 54 of 72

Which of the following non-pacemaker action potential phases involves fast sodium channels?

Phase 4
Phase 1
Phase 3
Phase 0
Phase 2

Question 55 of 72

What is the length of a normal PR interval?

0.06 to 0.1 seconds
0.12 to 0.2 seconds
0.08 to 0.1 seconds
0.06 to 0.3 seconds
0.08 to 0.2 seconds

Question 56 of 72

Why are the pressures inside the right side of the heart lower than those of the left side of the heart?

The right side of the heart only has to pump blood to the lungs, and the left side has to pump blood to the whole body.
There is no difference in the pressure of the right and left sides of the heart.
The right side of the heart has to overcome more pressure from the pulmonic valve.
The aortic valve is easier to open so the left ventricle can create more pressure.
The right side of the heart only receives half the blood volume that the left receives.

Question 57 of 72

Which of the following calcium channels allow for influx into the myocyte after beta-1 adrenergic stimulation?

P-type calcium channel
R-type calcium channel
N-type calcium channel
T-type calcium channel
L-type calcium channel

Question 58 of 72

Which of the following is the primary pacemaker of the heart?

Purkinje fibers
AV node
Bundle of His
Right and left bundle branches
SA node

Question 59 of 72

Which of the following phases of the non-pacemaker action potential involves an influx of calcium?

Phase 0
Phase 4
Phase 2
Phase 1
Phase 3

Question 60 of 72

Where is unipolar chest lead V4 placed?

6th intercostal space at the left midaxillary line
5th intercostal space at the left midclavicular line
4th intercostal space at the right midclavicular line
2nd intercostal space left of the sternum
3rd intercostal space right of the sternum

Question 61 of 72

Which heart sound is heard in early diastolic filling and may be an indicator of pathology?

S4
S2
S3
S1
S5

Question 62 of 72

Why does the Valsalva maneuver initially decrease blood pressure?

The increased intrathoracic pressure leads to decrease venous return. This leads to decreased preload.
The increased intrathoracic pressure leads to increased venous return and an increase in preload.
The increased intrathoracic pressure leads to increased venous return. This leads to increased preload
The decreased intrathoracic pressure leads to decreased venous return and then decreased preload.
The decreased intrathoracic pressure leads to increased venous return and then decreased preload.

Question 63 of 72

Which of the following are classified as non-pacemaker cells?

Cells in the AV node
Cells in the SA node
Ventricular myocytes
None of the options listed
Cells in the Bundle of His

Question 64 of 72

Which of the following likely causes the small downward deflection in the QRS complex of the ECG?

Left atrial depolarization
Base depolarization
Right atrial depolarization
Septal depolarization
Apex depolarization

Question 65 of 72

Which of the following findings is TRUE regarding the unipolar limb lead AVR?

Negative P wave
Small P wave
The QRS complex is always upright.
Small S wave
Tall R wave

Question 66 of 72

Which of the following parameters increases ventricular preload?

Decreased ventricular compliance
Decreased afterload
Increased ventricular inotropy
Increased heart rate
Increased atrial inotropy

Question 67 of 72

Which of the following factors will increase ventricular inotropy?

A decrease in heart rate
A decrease in afterload
An increase in sympathetic nervous system stimulation
A decrease in circulating catecholamines
Parasympathetic nervous system stimulation

Question 68 of 72

What is the usual resting membrane potential for ventricular myocytes?

-90 mV
Explanation
90 mV
75 mV
-60 mV

Question 69 of 72

Which direction will the ECG deflect when a depolarization travels toward a negative electrode?

No deflection
Downward
Upward
Inward
Outward

Question 70 of 72

What is the normal range for the mean electrical axis?

-50° to +90°
-10° to +50°
-30° to +100°
-20° to +110°
-90° to +100°

Question 71 of 72

Which of the following is used to express stroke volume?

End diastolic volume (EDV) – End systolic volume (ESV)
End systolic volume (ESV) + End diastolic volume (EDV)
End systolic volume (ESV) ÷ End-diastolic volume (EDV)
Cardiac output × Heart rate
End systolic volume (ESV) – Cardiac output

Question 72 of 72

Which of the following ions contributes most to the myocyte strength of contraction?

Chloride
Magnesium
Potassium
Calcium
Sodium

Cardiac Physiology 2023

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