Cardiac Cycle and Phases of the Heartbeat

Cardiac Cycle and Phases of the Heartbeat MDCAT MCQs with answers

15 past paper MCQs on Cardiac Cycle and Phases of the Heartbeat, from the Circulation unit of MDCAT Biology. The year each question appeared is shown where known; tap “Show answer” for the correct option and a short solution.

Read the notes first Practise the unit as a quiz

1.Which phase of the cardiac cycle is characterized by the opening of semilunar valves? (KMU MDCAT 2025)

  1. Atrial systole
  2. Atrial diastole
  3. Ventricular systole
  4. Ventricular diastole
Show answer

Correct answer: (c) Ventricular systole

The semilunar valves open when the ventricles contract and drive blood into the arteries.

2.Which part of the heart's conducting system delays the impulse from atria to the ventricles? (KMU MDCAT 2025)

  1. Sino-atrial node
  2. Atrio-ventricular node
  3. Purkinje fibers
  4. Atrio-ventricular valves
Show answer

Correct answer: (b) Atrio-ventricular node

The atrioventricular node holds the impulse back long enough for the atria to empty first.

3.The heartbeat sound “LUB” is produced on closure of (KMU MDCAT 2025)

  1. Aortic valve
  2. Atro-ventricular valves
  3. Pulmonary valves
  4. Semilunar valves
Show answer

Correct answer: (b) Atro-ventricular valves

The first sound is the shutting of the atrioventricular valves at the start of ventricular systole.

4.Which of the following event prevent backflow of blood from ventricles to atria during ventricular systole? (SIBA MDCAT 2025)

  1. Contraction of the atrial wall musles
  2. Closure of tricuspid and bicuspid valves
  3. Opening of semilunar valve
  4. Opening of tricuspid and bicuspid valves
Show answer

Correct answer: (b) Closure of tricuspid and bicuspid valves

The rising ventricular pressure snaps the tricuspid and bicuspid valves shut.

5.During diastole, the heart chambers: (SIBA MDCAT 2025)

  1. Relax and fill with blood
  2. Contract strongly
  3. Eject blood into arteries
  4. Remain closed
Show answer

Correct answer: (a) Relax and fill with blood

Diastole is the relaxation during which the chambers fill.

6.Atrioventricular valve closed during which phase of cardiac cycle: (SIBA MDCAT 2025)

  1. Ventricular systole
  2. Ventricular diastole
  3. Atrial systole
  4. Atrial diastole
Show answer

Correct answer: (a) Ventricular systole

They shut as the ventricles begin to contract, which is what makes the first heart sound.

7.During ventricular systole, which pressure changes occur? (SZABMU MDCAT 2025)

  1. Ventricular pressure rises above atrial and arterial pressures
  2. Atrial pressure rises above Ventricular pressure
  3. Ventricular pressure falls below arterial pressures
  4. Ventricular pressure falls below Atrial pressure
Show answer

Correct answer: (a) Ventricular pressure rises above atrial and arterial pressures

The contracting ventricle raises its pressure above both the atrium behind and the artery ahead.

8.Select the duration of cardiac cycle: (SZABMU MDCAT 2023)

  1. 0.6 sec
  2. 0.4 sec
  3. 0.7sec
  4. 0.8 sec
Show answer

Correct answer: (d) 0.8 sec

A cardiac cycle at seventy-five beats a minute lasts $0.8\,\mathrm{s}$.

9.Heartbeat is normally regulated by: (NUMS MDCAT 2022)

  1. Purkinje fibers
  2. AV bundle
  3. Sinoatrial node
  4. Bundle of His
Show answer

Correct answer: (c) Sinoatrial node

The sinoatrial node is the pacemaker that sets the rhythm.

10.The number of stages involved in a heart beat is: (PMC Practice 2021)

  1. 2
  2. 3
  3. 4
  4. 5
Show answer

Correct answer: (b) 3

A heartbeat runs atrial systole, ventricular systole and then diastole.

11.Which statement is correct about atrial systole? (UHS MDCAT 2018)

  1. Atria relax and ventricles contract
  2. Atria contract and ventricle also contract
  3. Ventricles remain relaxed while atria contracts
  4. Atria and ventricles are relaxed
Show answer

Correct answer: (c) Ventricles remain relaxed while atria contracts

In atrial systole the atria contract while the ventricles are still relaxed and filling.

12.Which one of the following act as a PACEMAKER in heart: (UHS MDCAT 2018)

  1. Bundle of His
  2. Atrioventricular node
  3. Atrioventricular bundles of fibers
  4. Sinoatrial node
Show answer

Correct answer: (d) Sinoatrial node

The sinoatrial node sets the rhythm of the heart.

13.A single cardiac cycle lasts about: (UHS MDCAT 2017)

  1. 0.008 sec
  2. 0.8 sec
  3. 8 sec
  4. 0.088 sec
Show answer

Correct answer: (b) 0.8 sec

At seventy-five beats a minute a cycle lasts $0.8\,\mathrm{s}$.

14.One complete heart beat consists of one systole and one diastole and lasts for about: (UHS MDCAT 2015)

  1. 0.8 sec
  2. 0.2 sec
  3. 0.4 sec
  4. 0.5 sec
Show answer

Correct answer: (a) 0.8 sec

At seventy-five beats a minute one cycle lasts $0.8\,\mathrm{s}$.

15.The heart beat cycle starts when electric impulses are generated from; (UHS MDCAT 2015)

  1. AV Node
  2. SV Node
  3. SA Node
  4. PQ Node www.PakLearningSpot.com
Show answer

Correct answer: (c) SA Node

The sinoatrial node is the pacemaker.

More in Circulation