autoregulation

1. The tendency of the blood flow to an organ or part to remain at or return to the same level despite changes in the pressure in the artery which conveys blood to it. 2. In general, any biologic system equipped with inhibitory feedback systems such that a given change tends to be largely or completely counteracted; e.g., baroreceptor reflexes form a basis for a. of the systemic arterial blood pressure.

- heterometric a. intrinsic regulation of the strength of cardiac contraction as a function of diastolic fiber length (volume), independent of afterload, autonomic nerves and other extrinsic influences. Heterometric a. is also known as the length-tension relationship, the relationship of end diastolic volume to end diastolic pressure, Starling law of the heart, and the Frank-Starling curve.

- homeometric a. intrinsic regulation of strength of cardiac contraction in response to influences that do not depend on change in fiber length, i.e., the Frank-Starling curve, ( e.g., the Anrep effect in which strength increases in response to increased afterload, and the Bowditch effect (treppe) in which strength increases in response to increased heart rate) and do not depend on extrinsic regulation ( e.g., in which strength increases in response to sympathetic nerve stimulation or norepinephrine).

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au·to·reg·u·la·tion .ȯt-ō-.reg-yə-'lā-shən n the maintenance of relative constancy of a physiological process by a bodily part or system under varying conditions esp the maintenance of a constant supply of blood to an organ in spite of varying arterial pressure <the influence of vasoactive agents on \autoregulation of renal flow (Science)>

au·to·reg·u·late -'reg-yə-.lāt vb, -lat·ed; -lat·ing

au·to·reg·u·la·to·ry -'reg-yə-lə-.tōr-ē, -.tȯr- adj

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au·to·reg·u·la·tion (aw″to-reg″u-laґshən) 1. the process occurring when some mechanism within a biological system detects and adjusts for changes within the system; exercised by negative feedback. 2. in circulatory physiology, the intrinsic tendency of an organ or tissue to maintain constant blood flow despite changes in arterial pressure, or the adjustment of blood flow through an organ in order to provide for its metabolic needs.