Cardiovascular and respiratory system

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The heart acts as the central pump in the human ‘central heating system’. It pumps blood to the body organs, tissues and muscles through the arteries and veins. The heart, lungs, veins and arteries, all under the control of the autonomic nervous system make up the cardiovascular system. Normally, the heart rate is dictated by the body’s needs. When at rest, the tissues, muscles and organs require fewer amounts of blood and oxygen and therefore there is a reduction in the pressure of the blood thus slowing down the heart rate. When active, the tissues, muscles and organs require an increased supply of oxygen and blood thus higher blood pressure, heart rate increase and more respirations. This response is usually involuntary and normal. (Your Heart's Electrical System, 2012)
Just like a regular pump, the heart needs energy and a power source. The heart creates its own electrical impulses and controls the path taken by the impulses through a specialized conduction pathway. This conduction pathway constitutes the sino-atrial (SA) node, the atrio-ventricular (AV) node, the Bundle of HIS, the left and right bundle branches and the purkinje fibres. The mentioned nodes are all in the heart. The SA node acts as the natural pacemaker of the heart. It releases electrical stimuli at a regular rate. This rate is dictated by the needs of the body. The SA node has special cells that create energy that makes the heart beat. Atrio-ventricular or the AV node on the other hand links the atria and ventricles. Through it, electrical signals pass from the atria down to the ventricles. The His-Purkinje System carries the electrical signals through all the ventricles. This makes them contract. His-Purkinje system consists of the His-Bundle which is the start of the system, the right bundle branch, left bundle branch and the purkinje fibres, which are located at the end of the system.
The SA node emits 60 to 100 electrical signals per minute, which is the heart rate or pulse. With each pulse, SA originating signals follow a natural electrical pathway through the heart walls. This movement of electrical signals causes the heart chambers to contract and relax. Under normal circumstances, chambers contract and relax in a coordinated way. At a normal rate, the heart beats are known as sinus rhythm. The conduction system automatically responds to the body’s changing need for oxygen. It senses the need for oxygen and responds with the proper heart rate. The heart’s normal rhythm can be disrupted by a problem in the heart’s electrical system. Abnormal heart rate rhythms are known as arrhythmia. It is abnormal for the heart to beat out of rhythm. During such times, the heart may not deliver enough blood in the body. There are different kinds of arrhythmia like atrial flutter and atrial fibrillation, which are fast heart beats and Bradycardia whic...