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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.
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 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 cardiac cycle is the performance of the human heart from the beginning of one heartbeat to the beginning of the next. It consists of two periods: one during which the heart muscle relaxes and refills with blood, called diastole, following a period of robust contraction and pumping of blood, dubbed systole. After emptying, the heart ...
A myokine is one of several hundred cytokines or other small proteins (~5–20 kDa) and proteoglycan peptides that are produced and released by skeletal muscle cells (muscle fibers) in response to muscular contractions. [1] They have autocrine, paracrine and/or endocrine effects; [2] their systemic effects occur at picomolar concentrations. [3] [4]
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).
When both the heart and lungs are healthy, pulmonary wedge pressure is equal to left ventricle diastolic pressure and can be used as a surrogate for preload. [3] Pulmonary wedge pressure will overestimate left ventricle pressure in people with mitral valve stenosis , pulmonary hypertension and other heart and lung conditions.