Autoregulation
Encyclopedia
Autoregulation is a process within many biological systems, resulting from some internal adaptive mechanism that works to adjust (or mitigate) the systems response to stimuli. While most systems of the body show some degree of autoregulation, it is most clearly observed in the kidney
, the heart
, and the brain
. Perfusion
of these organs (especially the latter two) is essential for life, and through autoregulation the body can divert blood (and thus, oxygen
) where it is most needed.
.
, is the heart's ability to increase contractility
and restore stroke volume
when afterload
increases. This is in contrast to heterometric regulation.
Kidney
The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...
, the heart
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
, and the brain
Brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...
. Perfusion
Perfusion
In physiology, perfusion is the process of nutritive delivery of arterial blood to a capillary bed in the biological tissue. The word is derived from the French verb "perfuser" meaning to "pour over or through."...
of these organs (especially the latter two) is essential for life, and through autoregulation the body can divert blood (and thus, oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
) where it is most needed.
Cerebral autoregulation
More so than most other organs, the brain is very sensitive to overperfusion, and cerebral autoregulation plays an important role in maintaining an appropriate blood pressure to that region. More detail is available at Cerebral perfusion pressureCerebral perfusion pressure
Cerebral perfusion pressure, or CPP, is the net pressure gradient causing blood flow to the brain . It must be maintained within narrow limits because too little pressure could cause brain tissue to become ischemic , and too much could raise intracranial pressure .-From resistance:CPP can be...
.
Homeometric autoregulation
Homeometric autoregulation, in the context of the circulatory systemCirculatory system
The circulatory system is an organ system that passes nutrients , gases, hormones, blood cells, etc...
, is the heart's ability to increase contractility
Contractility
Myocardial contractility is the intrinsic ability of the heart to contract independent of preload and afterload. Changes in the ability to produce force during contraction result from different degrees of binding between myosin and actin filaments...
and restore stroke volume
Stroke volume
In cardiovascular physiology, stroke volume is the volume of blood pumped from one ventricle of the heart with each beat. SV is calculated using measurements of ventricle volumes from an echocardiogram and subtracting the volume of the blood in the ventricle at the end of a beat from the volume...
when afterload
Afterload
Afterload is the tension or stress developed in the wall of the left ventricle during ejection. Following Laplace's law, the tension upon the muscle fibers in the heart wall is the product of the pressure within the ventricle, multiplied by the volume within the ventricle, divided by the wall...
increases. This is in contrast to heterometric regulation.
Coronary circulatory autoregulation
Since the heart is a very aerobic organ, needing oxygen for the efficient production of ATP & Creatine Phosphate from fatty acids (and to a smaller extent, glucose & very little lactate), the coronary circulation is auto regulated so that the heart receives the right flow of blood & hence sufficient supply of oxygen. If a sufficient flow of oxygen is met and the resistance in the coronary circulation rises (perhaps due to vasoconstriction), then the coronary perfusion pressure (CPP) increases proportionally, to maintain the same flow. In this way, the same flow through the coronary circulation is maintained over a range of pressures. This part of coronary circulatory regulation is known as auto regulation and it occurs over a plateau, reflecting the constant blood flow at varying CPP & resistance. The slope of a CBF (coronary blood flow) vs. CPP graph gives 1/Resistance.Renal autoregulation
There is "autoregulation" of renal blood flow and glomerular filtration rate in isolated kidneys. Howevever it is likely that both these parameters change to some extent in vivo, eg hypotension, during exercise. Autoregulation is the relative independence, from systemic blood pressure, of glomerular filtration rate and renal blood flow over the physiological range of mean arterial pressure (c.80-180 mmHg)See also
- Self-regulationSelf-regulationThe term self-regulation can signify:*Autoregulation*Homeostasis, in systems theory*Self-control, in sociology / psychology*Self-regulated learning, in educational psychology*Self-regulation theory , a system of conscious personal health management...
- HomeostasisHomeostasisHomeostasis is the property of a system that regulates its internal environment and tends to maintain a stable, constant condition of properties like temperature or pH...
- Renin-angiotensin systemRenin-angiotensin systemThe renin-angiotensin system or the renin-angiotensin-aldosterone system is a hormone system that regulates blood pressure and water balance....