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Many of the factors that regulate the heart rate also affect cardiac function by altering the stroke volume. While a number of variables are involved, stroke volume is dependent upon the difference between end diastolic volume and end systolic volume. The three primary factors involved are preload, afterload and contractility. [1]
The Purkinje fibers are further specialized to rapidly conduct impulses (having numerous fast voltage-gated sodium channels and mitochondria, and fewer myofibrils, than the surrounding muscle tissue). Purkinje fibers take up stain differently from the surrounding muscle cells because of having relatively fewer myofibrils than other cardiac cells.
The bundle of His (BH) [1]: 58 or His bundle (HB) [1]: 232 (/ h ɪ s / "hiss" [2]) is a collection of heart muscle cells specialized for electrical conduction.As part of the electrical conduction system of the heart, it transmits the electrical impulses from the atrioventricular node (located between the atria and the ventricles) to the point of the apex of the fascicular branches via the ...
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]
Within an in vivo intact heart, the action/response of the sympathetic nervous system is driven by precisely timed releases of a catecholamine, which is a process that determines the concentration of calcium ions in the cytosol of cardiac muscle cells. The factors causing an increase in contractility work by causing an increase in intracellular ...
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 binding of many types of coronaviruses, including the SARS-CoV-2 virus, through ACE2 receptors present in heart muscle may be responsible for direct viral injury leading to myocarditis. [25] In a study done during the 2002-2004 SARS outbreak , SARS viral RNA was detected in the autopsy of heart specimens in 35% of the patients in the ...
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).