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Cardiac muscle (also called heart muscle or myocardium) is one of three types of vertebrate muscle tissues, the others being skeletal muscle and smooth muscle.It is an involuntary, striated muscle that constitutes the main tissue of the wall of the heart.
Common abnormalities include those that affect the heart muscle that separates the two side of the heart (a "hole in the heart", e.g. ventricular septal defect). Other defects include those affecting the heart valves (e.g. congenital aortic stenosis), or the main blood vessels that lead from the heart (e.g. coarctation of the aorta).
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The conduction system consists of specialized heart muscle cells, situated within the myocardium. [3] There is a skeleton of fibrous tissue that surrounds the conduction system which can be seen on an ECG. Dysfunction of the conduction system can cause irregular heart rhythms including rhythms that are too fast or too slow.
Cardiac index is a critical parameter in evaluating cardiac performance and the adequacy of tissue perfusion. In healthy adults, the normal range of cardiac index is generally between 2.6 to 4.2 L/min/m².
Other tissues in skeletal muscle include tendons and perimysium. [3] Smooth and cardiac muscle contract involuntarily, without conscious intervention. These muscle types may be activated both through the interaction of the central nervous system as well as by innervation from peripheral plexus or endocrine (hormonal) activation.
Executive mental function was measured with standard tests, including the ability to say the sequence 1-A, 2-B, 3-C…, to name a number of animals in one minute, and with the Stroop test. [103] The study found that those individuals with lower skeletal muscle mass at the start of the study declined in their executive mental function ...
The section shows: 1) the opened ventricles contracting once per heartbeat—that is, once per each cardiac cycle; 2) the (partly obscured) mitral valve of the left heart; 3) the tricuspid and pulmonary valves of the right heart—note these paired valves open and close oppositely. + (The aortic valve of the left heart is located below the ...