Free Cardiac Cycle and Heartbeat MCQs with Answers
30 Cardiac Cycle and Heartbeat MCQs from Biology, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
The cardiac cycle describes atrial systole, ventricular systole and diastole, including pressure changes, blood movement and the opening or closing of heart valves. It also covers the conduction pathway from the sinoatrial node through the atrioventricular node, bundle of His and Purkinje fibres, and relates these events to heartbeat sounds.
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- A. atrioventricular node
- B. bundle of His
- C. sinoatrial node in the wall of the right atrium
- D. network of Purkinje fibres
Explanation: The sinoatrial node depolarises spontaneously about seventy times a minute and sets the rhythm, which is why the heartbeat is myogenic and…
Correct answer: sinoatrial node in the wall of the right atrium- A. slows the overall heart rate
- B. prevents the impulse from reaching the ventricles at all
- C. allows the semilunar valves to open early
- D. gives the atria time to empty into the ventricles before the ventricles contract
Explanation: A delay of about a tenth of a second lets atrial systole finish and the ventricles fill completely, so the following ventricular…
Correct answer: gives the atria time to empty into the ventricles before the ventricles contract- A. 5 dm3 per minute
- B. 0.5 dm3 per minute
- C. 14 dm3 per minute
- D. 50 dm3 per minute
Explanation: Cardiac output is stroke volume multiplied by heart rate, so 70 cm3 times 72 gives 5,040 cm3 per minute, which is about 5 dm3.
Correct answer: 5 dm3 per minute- A. blood rushing into the atria
- B. the closure of the semilunar valves
- C. contraction of the atrial walls
- D. the closure of the atrioventricular valves at the start of ventricular systole
Explanation: When the ventricles begin to contract the pressure inside them rises above atrial pressure, the tricuspid and bicuspid valves snap shut…
Correct answer: the closure of the atrioventricular valves at the start of ventricular systole- A. Atrial depolarization
- B. Ventricular depolarization
- C. Atrial repolarization
- D. Ventricular repolarization
Explanation: The QRS complex represents ventricular depolarization (contraction); the P wave is atrial depolarization.
Correct answer: Ventricular depolarization- A. Heart rate + Stroke volume
- B. Heart rate × Stroke volume
- C. Heart rate - Stroke volume
- D. Stroke volume only
Explanation: Cardiac output (mL/min) = Heart rate (beats/min) × Stroke volume (mL/beat).
Correct answer: Heart rate × Stroke volume- A. 2.8 Billion
- B. 3.7 Billion
- C. 4.2 Billion
- D. Infinite
Explanation: A typical estimate is about 70 beats/minute x 60 minutes/hour x 24 hours/day x 365 days/year x 70 years = 2,574,720,000 beats, or about…
Correct answer: 2.8 Billion- A. 1
- B. 2
- C. 3
- D. 4
Explanation: One cardiac cycle has three main stages: atrial systole, ventricular systole, and joint diastole.
Correct answer: 3- A. Bradycardia
- B. Tachycardia
- C. Braditachycardia
- D. Non of these
Explanation: Bradycardia means an abnormally slow heart rate, commonly defined in adults as fewer than 60 beats per minute at rest.
Correct answer: Bradycardia- A. Bradycardia
- B. Tachycardia
- C. Trachybradycardia
- D. Non of these
Explanation: Tachycardia is an abnormally rapid heart rate, often described in adults as more than 100 beats per minute at rest.
Correct answer: Tachycardia- A. The ventricles are fully contracted
- B. The ventricles start to relax
- C. The bicuspid and tricuspid valves suddenly close
- D. The semilunar valves are closed
Explanation: The “lub” sound is produced when the atrioventricular valves, the bicuspid and tricuspid valves, suddenly close at the beginning of…
Correct answer: The bicuspid and tricuspid valves suddenly close- A. Atrial systole
- B. Ventricular systole
- C. Atrial diastole
- D. Ventricular diastole
Explanation: The QRS complex records ventricular depolarisation, which initiates ventricular contraction or ventricular systole.
Correct answer: Ventricular systole- A. Opening of inlet valve
- B. Closure of inlet valve
- C. Opening of outlet valve
- D. Closure of outlet valve
Explanation: The lubb sound occurs when the atrioventricular, or inlet, valves close at the beginning of ventricular systole.
Correct answer: Closure of inlet valve- A. SA node > AV node > Purkinje fibres > ventricles
- B. SA node > Purkinje fibres > AV node > ventricles
- C. AV node > SA node > Purkinje fibres > ventricles
- D. AV node > Purkinje fibres > SA node > ventricles
Explanation: The correct pathway of nerve impulse during the excitation and contraction of the human heart is: SA node > AV node > Purkinje fibres >…
Correct answer: SA node > AV node > Purkinje fibres > ventricles- A. Option A
- B. Option B
- C. Option C
- D. Option D
Explanation: During ventricular systole, ventricular pressure exceeds atrial pressure to pump blood into aorta, AV valves closes to prevent backflow of…
Correct answer: Option B16. When blood pressure is the highest in the aorta, the atrioventricular and semilunar valves would:
- A. Option A
- B. Option B
- C. Option C
- D. Option D
Explanation: When pressure is highest in aorta both AV valves and semilunar are closed because ventricular contraction has just completed.So C is…
Correct answer: Option C- A. Aortic pressure exceeds ventricular pressure
- B. Left atrial pressure exceeds left ventricular pressure
- C. Right ventricular pressure exceeds right atrial pressure
- D. Pulmonary trunk pressure exceeds ventricular pressure
Explanation: The tricuspid valve is located between the right atrium and the right ventricle of the heart.
Correct answer: Right ventricular pressure exceeds right atrial pressure- A. A
- B. B
- C. C
- D. D
Explanation: During atrial systole, the atria contract to push blood into the ventricles. Therefore, the ventricles are relaxed at this stage.
Correct answer: B- A. Ventricular repolarization
- B. Ventricular depolarization
- C. Atrial repolarization
- D. Atrial depolarization
Explanation: The T wave in an ECG (electrocardiogram) represents ventricular repolarization, indicating the recovery of the ventricles before the next…
Correct answer: Ventricular repolarization- A. P wave
- B. QRS Complex
- C. T wave
- D. PQRS
Explanation: The P wave on an electrocardiogram (ECG) represents atrial depolarization, which is the electrical activation that initiates the…
Correct answer: P waveCardiac Cycle and Heartbeat MCQs: common questions
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