A) fast heart rate
B) slow heart rate
C) stop heart rate
D) normal heart rate
Correct Answer: A
Solution :
A condition when heartbeat exceeds 100 beats per minute is called Tachycardia. It results during active and stress states due to release of noradrenalin at their terminal, which accelerates the contraction of cardiac muscles, increase both force and rate of heartbeat. A condition when heartbeat is reduced to less than 60 per minute is called Bradycardia. The stimulation of decreasing heartbeat, is carried to the heart by parasympathetic motor fibres. On stimulation, these fibres release acetylcholine at their cardiac terminals, which relates the activity of the fibres of SA and AV nodes. A condition, in which stoppage of heart occurs, is called cardiac arrest. In this condition, there is no heart beat and the heart fails to pump blood, usually leads to death. Normal heart beat of human is 75 times per minute. The heart regularly and rhythmically contacts and relaxes at short intervals. This inherent activity is called pulsatun or beating. Each heart beat has two phases Contraction phase or systole and Relaxation phase or diastole.
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