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Normal ECG

Electrocardiograms (ECGs) have been around for quite some time. In 1887, a British physiologist, Augustus D. Waller of St. Mary’s Medical School in London, published the first human ECG. 

However, it wasn’t until the early 1900s that the ECG became a useful clinical tool, mainly as a result of the phenomenal work of Willem Einthoven, a Dutch physician and physiologist. In 1924, Einthoven won the Nobel Prize for inventing the first practical electrocardiogram.

Imagen source:

Above is a photograph of a complete ECG showing the manner in which the electrodes are attached to the patient. In this case, the hands and one foot are immersed in jars of salt water.

Below shows how ECGs are done today.

Image source - NHLBI

Image source : St Judes Medical

The heart has  an electrical system, which allows the contractions of the  chambers of the 
heart t
o occur in a synchronous fashion.

If all the nerves from the body’s nervous system are cut, the heart will continue to beat. Even more fantastic, is that if the heart is cut into pieces, each individual piece will continue to beat. This is because of the presence of specialized conductive tissue which makes up the electrical system of the heart.

At the beginning of each heart beat, an electrical impulse is generated in the heart’s own natural pacemaker, the sinus node.  A node is simply defined as a localized mass of tissue. It is then transmitted throughout both atria and pauses at another node, which is present at the junction of the atria and ventricles, the AV node. During this pause, the atria simultaneously contract, filling the ventricles with the optimum amount of blood. The impulse then proceeds to activate both ventricles via the left and right bundle branches. Ventricular contraction then occurs. This whole process takes about ¾ of a second

 Image scource - Cleveland Clinic

An electrocardiogram (EKG, ECG,) is a recording of the electrical activity of the heart.

Image source - http://www.exercise-science-guide.com/blo

The P wave represents electrical stimulation of the atria.
The QRS represents electrical fo the ventricles.
The T wave represents relaxation of the ventricles.

Below is a normal ECG.

To learn more about ECGs go to

ECG:Reading the waves on the Merck Manual Home Health Handbook site