The heart is a natural pacemaker which regulates the rate of our hearts. It is in the upper portion of the right atrium. Each spark travels across a specialised electrical pathway and stimulates the muscle wall of the four chambers of the heart to contract. The atria is first stimulated and emptied and the two ventricles are electrically stimulated. Adrenaline is like an accelerator in a car it causes the sinus node to increase the number of sparks per minute which increases the heart rate. The heart normally beats around 72 times per minute and the sinus node speeds up during exertion, stress, fever or if our body needs an extra boost of blood supply.
The electrical activity within our heart can be recorded on a ECG (electrocardiogram).
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