Myocardium is the muscular middle layer of the wall of the heart
. It is composed of spontaneously contracting cardiac muscle
fibers which allow the heart to contract. Heart contraction is an autonomic (involuntary) function of the peripheral nervous system
. The myocardium is surrounded by the epicardium
(outer layer of the wall of the heart) and the endocardium
(inner layer of the heart).
Function of the Myocardium
Myocardium stimulates heart contractions to pump blood from the ventricles
and relaxes the heart to allow the atria
to receive blood. These contractions produce what is known as a heart beat. The beating of the heart drives the cardiac cycle
which pumps blood to cells
of the body.