Intrinsic+Conduction+System


 * __Intrinsic Conduction System__**

Since cardiac muscle can contract spontaneously and independently, the body needs a system to regulate the contractions and maintain a regular heartbeat. This is the job of the Intrinsic Conduction System (ICS). The Intrinsic Conduction System consists of a specialized cross of muscle and nerve tissue found only in the heart. It regulates the beating of the heart by causing a depolarization of cardiac muscle from the atria to the ventricles.

The ICS is explained in a [|Well Labeled Video].

A few things not mentioned in the video:
 * The Vagus nerve is nerve that connects the heart to the brainstem and can increase or decrease heart rate. Without the Vagus nerve, the heart would naturally beat at approximately 75 beats per minute.
 * SA Node stands for Sinoatrial Node.
 * AV Node stands for Atrioventricular Node which slightly delays the electrical signal sent by the SA Node. This gives the ventricles time to completely fill-up and allows the valves to close, therefore letting the heart pump more efficiently.
 * The Atrioventricular Bundle is also known as the Bundle of His.


 * __ECG/EKG__**

ECG stands for Electrocardiogram. EKG also stands for Electrocardiogram because "cardio" is spelled with a "k" in German. The ECG/EKG is used to measure the normality of someone's heartbeat by measuring the electrical activity in their heart.

On an ECG/EKG, a regular single heartbeat would appear as a tall spike with two small humps on either side of it. Each heartbeat is connected to others by a straight horizontal line which represents the time in between beats (see diagram below).

The components of the electrical activity in the heart are labeled P, Q, R, S, and T (see diagram below).
 * The P-Wave is an electrical current that causes a depolarization of the atria.
 * The QRS Complex is an electrical current that causes the contraction of the ventricles.
 * More specifically, Q is the current down the septum and RS is the current through the ventricles.
 * The T-Wave is the electrical current causing the repolarization of the ventricles.
 * The repolarization of the atria is masked by the QRS complex.



[|Test Your Knowledge of the ICS!]