homeometric heterometric riboswitch autoregulation inotropy 3334 dalgarno juxtaglomerular densa arteriole 0967 gfr 9148 bowditch cardiomyocyte tubuloglomerular macula jablonka diastolic angiotensin edvinsson afterload 6772 thirumalai nrneurol renin 201x 9538 myogenic contractility
autoregulatory increase of blood flow to a tissue
Autoregulation - wikipedia Autoregulation Jump to : navigation , search Autoregulation is a process within many biological systems , resulting from an internal adaptive mechanism that works to adjust ( or mitigate ) that system 's 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 is essential for life , and through autoregulation the body can divert blood ( and thus , oxygen ) where it is most needed . Contents ( hide ) 1 Cerebral autoregulation 2 Homeometric and heterometric autoregulation of the heart 3 Coronary circulatory autoregulation 4 Renal autoregulation 5 Autoregulation of genes 6 See also 7 References Cerebral autoregulation ( edit ) Main article : Cerebral autoregulation More so than most other organs , the brain is very sensitive to increased or decreased blood flow , and several mechanisms ( metabolic , myogenic , and neurogenic ) are involved in maintaining an appropriate cerebral blood pressure . Brain blood flow autoregulation is abolished in several disease states such as traumatic brain injury , stroke , brain tumors , or persistent abnormally high CO2 levels . Homeometric and heterometric autoregulation of the heart ( edit ) Homeometric autoregulation , in the context of the circulatory system , is the heart 's ability to increase contractility and restore stroke volume when afterload increases . Homeometric autoregulation occurs independently of cardiomyocyte fiber length , via the Bowditch and / or Anrep effects . Via the Bowditch effect , positive inotropy occurs secondary to an increased cardiac frequency . The exact mechanism for this remains unknown , but it appears to be the result of an increased exposure of the heart to contractile substances arising from the increased flow caused by an increased cardiac frequency . Via the Anrep effect , positive inotropy occurs secondary to increased ventricular pressure . This is in contrast to heterometric regulation , governed by the Frank - Starling law , which results from a more favorable positioning of actin and myosin filaments in cardiomyocytes as a result of changing fiber lengths . Coronary circulatory autoregulation ( edit ) 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 ( edit ) Main article : Tubuloglomerular feedback Regulation of renal blood flow is important to maintaining a stable glomerular filtration rate ( GFR ) despite changes in systemic blood pressure ( within about 80 - 180 mmHg ) . In a mechanism called tubuloglomerular feedback , the kidney changes its own blood flow in response to changes in sodium concentration . The sodium chloride levels in the urinary filtrate are sensed by the macula densa cells at the end of the ascending limb . When sodium levels are moderately increased , the macula densa releases ATP and reduces prostaglandin E2 release to the juxtaglomerular cells nearby . The juxtaglomerular cells in the afferent arteriole constrict , and juxtaglomerular cells in both the afferent and efferent arteriole decrease their renin secretion . These actions function to lower GFR . Further increase in sodium concentration leads to the release of nitric oxide , a vasodilating substance , to prevent excessive vasoconstriction . In the opposite case , juxtaglomerular cells are stimulated to release more renin , which stimulates the renin -- angiotensin system , producing angiotensin I which is converted by Angio - Tensin Converting Enzyme ( ACE ) to angiotensin II . Angiotensin II then causes preferential constriction of the efferent arteriole of the glomerulus and increases the GFR . Autoregulation of genes ( edit ) This is so - called `` steady - state system '' . An example is a system in which a protein P that is a product of gene G `` positively regulates its own production by binding to a regulatory element of the gene coding for it , '' and the protein gets used or lost at a rate that increases as its concentration increases . This feedback loop creates two possible states `` on '' and `` off '' . If an outside factor makes the concentration of P increase to some threshold level , the production of protein P is `` on '' , i.e. P will maintain its own concentration at a certain level , until some other stimulus will lower it down below the threshold level , when concentration of P will be insufficient to make gene G express at the rate that would overcome the loss or use of the protein P . This state ( `` on '' or `` off '' ) gets inherited after cell division , since the concentration of protein a usually remains the same after mitosis . However , the state can be easily disrupted by outside factors . Similarly , this phenomenon is not only restricted to genes but may also apply to other genetic units , including mRNA transcripts . Regulatory segments of mRNA called a Riboswitch can autoregulate its transcription by sequestering cis - regulatory elements ( particularly the Shine - Dalgarno sequence ) located on the same transcript as the Riboswitch . The Riboswitch stem - loop has a region complementary to the Shine - Dalgarno but is sequestered by complimentary base pairing in the loop . With sufficient ligand , the ligand may bind to the stem - loop and disrupt intermolecular bonding , resulting in the complimentary Shine - Dalgarno stem - loop segment binding to the complimentary Riboswitch segment , preventing Ribosome from binding , inhibiting translation . See also ( edit ) Look up autoregulation in Wiktionary , the free dictionary . Homeostasis Renin -- angiotensin system References ( edit ) Jump up ^ Autoregulation Jump up ^ Figaji , Anthony A. ; Eugene Zwane ; A. Graham Fieggen ; Andrew C. Argent ; Peter D. Le Roux ; Peter Siesjo ; Jonathan C. Peter ( 2009 ) . `` Pressure autoregulation , intracranial pressure , and brain tissue oxygenation in children with severe traumatic brain injury '' . Journal of Neurosurgery . Pediatrics. 4 ( 5 ) : 420 -- 428 . doi : 10.3171 / 2009.6. PEDS096 . ISSN 1933 - 0715 . PMID 19877773 . Jump up ^ Budohoski K.P. ; Czosnyka M. ; Kirkpatrick P.J. ; Smielewski P. ; Pickard J.D. ( 2013 ) . `` Clinical relevance of cerebral autoregulation following subarachnoid haemorrhage '' . Nat. Rev. Neurol. 9 ( 3 ) : 152 -- 63 . doi : 10.1038 / nrneurol. 2013.11 . PMID 23419369 . Jump up ^ Paulson , O.B. ; S. Strandgaard ; L. Edvinsson ( 1990 ) . `` Cerebral autoregulation '' . Cerebrovascular and Brain Metabolism Reviews . 2 ( 2 ) : 161 -- 192 . ISSN 1040 - 8827 . PMID 2201348 . Jump up ^ Panerai , R.B. ; S.T. Deverson ; P. Mahony ; P. Hayes ; D.H. Evans ( 1999 ) . `` Effect of CO2 on dynamic cerebral autoregulation measurement '' . Physiological Measurement. 20 ( 3 ) : 265 . doi : 10.1088 / 0967 - 3334 / 20 / 3 / 304 . ISSN 0967 - 3334 . PMID 10475580 . Retrieved 2015 - 01 - 24 . Jump up ^ Sarnoff SJ , Mitchell JH , Gilmore JP , Remensnyder JP ( 1960 ) . `` Homeometric autoregulation in the heart '' ( PDF ) . Circulation Research . 8 ( 5 ) : 1077 -- 1091 . doi : 10.1161 / 01. res. 8.5. 1077 . PMID 13746560 . ^ Jump up to : Monroe , R.G. ; Gamble , W.J. ; Lafarge , C.G. ; Vatner , S.F. ( 1974 - 01 - 01 ) . Porter , Ruth ; Fitzsimons , David W. , eds . Ciba Foundation Symposium 24 - Physiological Basis of Starling 's Law of the Heart . John Wiley & Sons , Ltd . pp. 257 -- 290 . doi : 10.1002 / 9780470720066. ch14 . ISBN 9780470720066 . Jump up ^ Hall , John E. ( 2016 ) . Guyton and Hall Textbook of Medical Physiology . Philadelphia : Elsevier . p. 119 . ISBN 9781455770052 . Jump up ^ Bell , P. Darwin ; Peter Komlosi ; Zhi - Ren Zhang ( 2009 ) . `` ATP as a mediator of macula densa cell signalling '' . Purinergic Signalling. 5 ( 4 ) : 461 -- 471 . doi : 10.1007 / s11302 - 009 - 9148 - 0 . ISSN 1573 - 9538 . PMC 2776136 . PMID 19330465 . ^ Jump up to : Komlosi , P. ; A. Fintha ; P.D. Bell ( 2004 ) . `` Current mechanisms of macula densa cell signalling '' . Acta Physiologica Scandinavica. 181 ( 4 ) : 463 -- 469 . doi : 10.1111 / j. 1365 - 201X. 2004.01319. x . ISSN 0001 - 6772 . PMID 15283759 . ^ Jump up to : Jablonka E. ; Lachmann M. ; Lamb M.J. ( 1992 ) . `` Evidence , Mechanisms and Models for the Inheritance of Acquired Characters '' . Journal of Theoretical Biology . 158 ( 2 ) : 245 -- 268 . doi : 10.1016 / s0022 - 5193 ( 05 ) 80722 - 2 . Jump up ^ Lin , Jong - Chin ; Thirumalai , D. ( 2012 - 10 - 25 ) . `` Gene Regulation by Riboswitches with and without Negative Feedback Loop '' . Biophysical Journal . 103 ( 11 ) : 12 . arXiv : 1210.6998 . doi : 10.1016 / j. bpj. 2012.10. 026 . PMC 3514527 . PMID 23283231 . <Th_colspan="2"> ( hide ) Physiology of the cardiovascular system Heart Cardiac output Cardiac cycle Cardiac output Heart rate Stroke volume Stroke volume End - diastolic volume End - systolic volume Afterload Preload Frank -- Starling law Cardiac function curve Venous return curve Wiggers diagram Pressure volume diagram Ultrasound Fractional shortening = ( End - diastolic dimension End - systolic dimension ) / End - diastolic dimension Aortic valve area calculation Ejection fraction Cardiac index Heart rate Cardiac pacemaker Chronotropic ( Heart rate ) Dromotropic ( Conduction velocity ) Inotropic ( Contractility ) Bathmotropic ( Excitability ) Lusitropic ( Relaxation ) Conduction Conduction system Cardiac electrophysiology Action potential cardiac atrial ventricular Effective refractory period Pacemaker potential Electrocardiography P wave PR interval QRS complex QT interval ST segment T wave U wave Hexaxial reference system Chamber pressure Central venous Right atrial ventricular pulmonary artery wedge Left atrial ventricular Aortic Other Ventricular remodeling Vascular system / Hemodynamics Blood flow Compliance Vascular resistance Pulse Perfusion Blood pressure Pulse pressure Systolic Diastolic Mean arterial pressure Jugular venous pressure Portal venous pressure Regulation of BP Baroreflex Kinin -- kallikrein system Renin -- angiotensin system Vasoconstrictors Vasodilators Autoregulation Myogenic mechanism Tubuloglomerular feedback Cerebral autoregulation Paraganglia Aortic body Carotid body Glomus cell Retrieved from `` https://en.wikipedia.org/w/index.php?title=Autoregulation&oldid=827281130 '' Categories : Physiology Talk Contents About Wikipedia Deutsch Eesti Français Galego Italiano Српски / srpski Edit links This page was last edited on 23 February 2018 , at 20 : 29 . 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