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This is one of the 3 main muscle structures
Others are as follows
- Skeletal Muscle
- Smooth Muscle
 
Cardiac muscle is found in the Heart and are somewhat similar to skeletal muscle cells.  Cardiac muscle has a striated appearance.

Contraction of this muscle group causes the movement of blood throughout the body.  It also allows for blood to go from the Atria to the Ventricles of the heart.

Cardiac muscle is a main contributor to the Cardiovascular System and Circulatory.

Elements such as nutrition, oxygen, and energy molecules are essential.  Carbon
dioxide and other waste products are removed as well.

Difference between this muscle type and others are dramatic!

Cardiac muscle is almost unsusceptible to fatigue.  There is a very large amount
of mitochondria that allow for production of energy molecules such as ATP.
There are many myoglobins that help in the binding of oxygen. 
Oxygen is required and essential to pumping of blood.

The muscle itself has segments referred to as Thick and Thin.
Actin and myosin are found in both cardiac and skeletal muscles.

Calcium ions and Sodium ions are required in cardiac muscles to contract.
Calcium then binds to troponin which begins the contraction.

The central nervous system has a limited function in the contraction of
the heart.  The CNS only controls the rate of contraction – it will speed up
or slow down the heart.

There are specific cells in the sinoatrial node (SA node) that regulate heartbeat. 
These cells are called “pacemaker” cells.  If the SA node has lost function either
temporarily or permanently then cells from the atrioventricualar node (AV node) 
will then become the “pacemaker” cells.