Heart Beat


 
 
Concept Explanation
 

Heart Beat

The heart is made up of cardiac muscle. Cardiac muscle naturally contracts and relaxes without any input from the brain. This can happen because cardiac muscle is an involuntary muscle. This means that the muscle works without you thinking about it or controlling it . The rhythm of the heartbeat is initiated by a small patch of muscle , called a pacemaker. 

The rhythm of relaxation and contraction of pacemaker sets the rhythm for the heartbeat. The pacemaker stimulates both atria to contract simultaneously. When the stimulus reaches the tissue between the atria and the ventricles, another small patch of specialised tissue stimulates both ventricle to contract.

If the impulses in the ventricles become disorganised because the stimulus is not picked up correctly, then the muscles of the ventricle begin to twitch spasmodically. This is a condition known as ventricular fibrillation. Blood flow stops and unless the heart rhythm is restarted, death will follow swiftly.

A defibrillator is used to deliver electric current to the heart, in an attempt to restore the heart's natural rhythm and save the person's life. Defibrillators are found in hospital emergency rooms, ambulances, commercial aircrafts, shopping and surf lifesaving clubs.

                         

Sample Questions
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Question : 1

If the impulses in the ventricles become disorganised because the stimulus is not picked up correctly, then the muscles of the ventricle begin to  _____________________

Right Option : B
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Explanation
Question : 2

If the impulses in the ventricles become dis - organised because the stimulus is not picked up correctly, then the muscles of the ventricle begin to twitch spasmodically. This is a condition known as _____________________

Right Option : B
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Explanation
Question : 3

Cardiac muscles are which type of muscles ?

Right Option : B
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Explanation
 
 


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