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This is done by a number of mechanisms: [citation needed] Parasympathetic activation. If the heart is experiencing anoxia, hypercapnia (increased CO 2) or acidosis, the heart cells will enter a state of dysfunction and not work properly. Correct sarcomere crossbridges will not form the heart becomes less efficient (leading to myocardial failure).
These cells, unlike most other cells within the heart, can spontaneously produce action potentials. [5] These action potentials travel along the cell membrane (sarcolemma) , as impulses, passing from one cell to the next through channels, in structures known as gap junctions .
The cells that make up the SA node are specialized cardiomyocytes known as pacemaker cells that can spontaneously generate cardiac action potentials. These signals are propagated through the heart's electrical conduction system. [1] [2] Only one percent of the heart muscle cells are conductive, the rest of the cardiomyocytes are contractile.
The Purkinje fibers transmit the signals more rapidly to stimulate contraction of the ventricles. [2] 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.
The contractility of both a healthy heart and a damaged heart could be increased through application of appropriate signals during the absolute refractory period of the cardiac muscle cells. [47] [48] An implantable cardiac contractility modulation device was received by a patient for the first time in 2001.
The heart muscle may become inflamed in a condition called myocarditis, [46] most commonly caused by a viral infection [47] but sometimes caused by the body's own immune system. [48] Heart muscle can also be damaged by drugs such as alcohol, long standing high blood pressure or hypertension, or persistent abnormal heart racing. [49]
The main role of a sinoatrial node cell is to initiate action potentials of the heart that can pass through cardiac muscle cells and cause contraction. An action potential is a rapid change in membrane potential, produced by the movement of charged atoms .
Heart tissue, like all cells in the body, needs to be supplied with oxygen, nutrients and a way of removing metabolic wastes. This is achieved by the coronary circulation, which includes arteries, veins, and lymphatic vessels. Blood flow through the coronary vessels occurs in peaks and troughs relating to the heart muscle's relaxation or ...