Cardiac Cycle


 
 
Concept Explanation
 

Cardiac Cycle

Human Heart

Structure of Human Heart :-

The heart is a muscular, conical and dark red coloured  organ that act as a pump of the blood   circulatory system in our body.In man, the heart weighs about 0.43 % of the body.The heart is made up of special type of muscles known as cardiac muscles. These muscles contract with considerable force, squeezing the blood out into the arteries which carries it to the different body parts. A single cycle of circulation of blood into the heart is known as cardiac cycle.

  • Cardiac cycle: It is the sequence of alternating contraction and relaxation of the atria and ventricles of the heart to pump blood through out the body. It lasts approximately 0.8 seconds.The heart beats non stop throughout one’s life.
  • It is also known as heart beat. The number of times the heart beats per minute is called as heart rate.For a normal adult human, it is about 72 times per minute.It increases during physical excercise.
  • A single cardiac cycle can be divided into two basic steps:
  • Diastole It represents the time period when the ventricles are relaxed.
  • Systole: It represents the time during when the left and the right ventricles contract and eject blood into the aorta and pulmonary artery.
  • Mechanism  of Cardiac Cycle :-

  • At the start of the cycle , during ventricular diastole the heart relaxes and expands while receiving blood through both atria.This stage represents  ventricular diastole. It lasts for 0.4 sec.
  • In the next step their occur artrial contraction which pushes blood into the ventricles. After the release of blood their occur closure of artrioventricular valve . This takes 0.1 sec.
  • After receiving blood ventricular systole or contraction of ventricles occur. It results in the pumping of blood to different blood vessels which pump blood to the body and the lungs.At this stage semilunar valves(guarding pulmonary artery) opens.It takes about 0.3 sec.
  • For a short period both atria and ventricle relaxes called as joint diastole.
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    Sample Questions
    (More Questions for each concept available in Login)
    Question : 1

    In the cardiac cycle both atria and ventricle relaxes for a short period. This is known as _____________________ .

    Right Option : C
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    Explanation
    Question : 2

    In human being the duration of cardiac cycle is ___________

    Right Option : A
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    Explanation
    Question : 3

    Which of the following are correct ?

    (a) During ventricular diastole the heart relaxes and expands while receiving blood through both atria.This stage represents ventricular diastole. It lasts for 0.4 sec.

    (b) Artrial contraction pushes blood into the ventricles.

    (c) Cardiac cycle a short period both atria and ventricle relaxes called as joint diastole.

    Right Option : D
    View Explanation
    Explanation
     
     
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