{"id":89319,"date":"2018-02-17T16:12:00","date_gmt":"2018-02-17T16:12:00","guid":{"rendered":""},"modified":"2023-01-06T20:33:25","modified_gmt":"2023-01-06T20:33:25","slug":"baroreceptorii","status":"publish","type":"post","link":"https:\/\/cvnextjob.com\/index.php\/2018\/02\/17\/baroreceptorii\/","title":{"rendered":"Baroreceptorii"},"content":{"rendered":"
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Baroreceptorii sinocarotidieni<\/span><\/div>\n
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Sunt situa\u0163i deasupra carotidei primitive, pe carotida intern\u0103 se afl\u0103 o por\u0163iune dilatat\u0103 sub form\u0103 de bulb numit sinus carotidian. Sunt cei mai bine studia\u0163i deoarece sinusul carotidian poate fi izolat vascular \u015fi perfuzat f\u0103r\u0103 lezarea inerva\u0163iei locale.<\/span><\/div>\n
Aceste forma\u0163iuni receptoare sunt stimulate prin distensia transversal\u0103 (dilatare) sau longitudinal\u0103 (alungite) consecutive varia\u0163iilor presiunii arteriale fiind mai sensibili la presiunea pulsatil\u0103 (imprimat\u0103 de sistolele ventriculare) dec\u00e2t la cea stagnant\u0103. Desc\u0103rc\u0103rile de impulsuri din fiecare unitate baroreceptoare \u00eencep la o anumit\u0103 presiune (=prag de 60 mmHg) \u015fi se intensific\u0103 progresiv pe m\u0103sura cre\u015fterii presiunii p\u00e2n\u0103 la un anumit nivel maxim ce nu dep\u0103\u015fe\u015fte 180-200mmHg.<\/span><\/div>\n
Impulsurile desc\u0103rcate de baroreceptorii sinocarotidieni se transmit ascendent \u00een nucleul tractului solitar pe fibrele nervului sinusal (nervul Hering ramur\u0103 a glosofaringianului ce con\u0163ine aproximativ 650-700 fibre dintre care 3,5% sunt fibre groase cu diametrul de 3-5 \u00b5m \u015fi prag de desc\u0103rcare \u00eentre 120- 150 mmHg iar 17,5% sunt fibre sub\u0163iri ce deservesc chemoreceptori.<\/span><\/div>\n
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                        Baroreceptorii aortici  <\/span><\/div>\n
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            Sunt situa\u0163i la nivelul crosei aortice la emergen\u0163a arterei subclaviculare.<\/span><\/div>\n
Au un prag de stimulare mai ridicat (110mmHg) ceea ce justific\u0103 implicarea lor numai la cre\u015fterile presionale.<\/span><\/div>\n
Impulsurile aferente de la nivelul receptorilor aortici se transmit ascendent prin nervii aortici drept \u015fi st\u00e2ng (fibre nemielinizate ce conduc cu vitez\u0103 redus\u0103 1-2m\/s) sau ale nervului vag.<\/span><\/div>\n
Cre\u015fterile presiunii arteriale (sau compresia carotidelor deasupra bifurca\u0163ie ) m\u0103resc frecven\u0163a impulsurilor p\u00e2n\u0103 la un anumit nivel propor\u0163ional cu cre\u015fterea presiunii, impulsuri care determin\u0103 at\u00e2t sc\u0103derea debitului cardiac (scade frecven\u0163a \u015fi contractilitatea cardiac\u0103) c\u00e2t \u015fi a rezisten\u0163ei vasculare (reflex depresor).<\/span><\/div>\n
            Sc\u0103derea presiunii arteriale (sau compresia carotidei comune) stimuleaz\u0103 baroreceptorii sinocarotidieni \u015fi aortici determin\u00e2nd: tahicardie, vasoconstric\u0163ie,    cre\u015fterea presiunii \u015fi a debitului cardiac (reflex presor). Receptorii sinocarotidieni \u015fi aortici a\u015feza\u0163i la o zon\u0103 de r\u0103scruce a circula\u0163iei, de unde pleac\u0103 spre creier cea mai mare cantitate de s\u00e2nge, reprezint\u0103 mecanisme de siguran\u0163\u0103 care contrabalanseaz\u0103 varia\u0163iile bru\u015fte ale presiunii arteriale sistemice men\u0163in\u00e2nd astfel o iriga\u0163ie constant\u0103 a creierului ceea ce justific\u0103 denumirea de nervi tamponi dat\u0103 de Wright. Efectele baroreceptorilor sunt de scurt\u0103 durat\u0103 datorit\u0103 adapt\u0103rii rapide (1-2 zile) la nivelul presional, modificare ce  face ca ace\u015ftia s\u0103 participe numai la corectarea rapid\u0103 a modific\u0103rilor presionale.<\/span><\/div>\n
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Baroreceptorii atriali               <\/span><\/div>\n
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Sunt situa\u0163i subendocardic, endocardul atrial fiind zona cardiac\u0103 cu cea mai bogat\u0103 inerva\u0163ie. Au densitate mare \u00een atriul drept la nivelul orificiului de v\u0103rsare ale venei cave dec\u00e2t \u00een atriul st\u00e2ng (\u00een jurul jonc\u0163iunilor venei pulmonare. Sunt de dou\u0103 tipuri:<\/span><\/div>\n
 <\/span><\/div>\n
\u00b7                  <\/span><\/span>tipul A care descarc\u0103 \u00een sistol\u0103 \u015fi care ar determina reflexul Bainbridge;<\/span><\/div>\n
\u00b7        <\/span><\/span>tipul B care descarc\u0103 \u00een diastol\u0103 (mai pu\u0163in sensibili datorit\u0103 situ\u0103rii lor \u00een paralel cu musculatura atrial\u0103) \u015fi care ar determina inhibi\u0163ia secretore de AND (prin aceasta ar controla \u00een permanen\u0163\u0103 volumul vascular). Stimularea receptorilor atriului drept prin cre\u015fterea \u00eentoarcerii venoase determin\u0103 cre\u015fterea frecven\u0163ei cardiace de\u015fi cercet\u0103rile recente privind efectul tahicardizant (descoperit ini\u0163ial de Bainbridge \u00een 1915) au precizat c\u0103 acesta se datoreaz\u0103 20-27% influen\u0163elor exercitate de c\u0103tre distensia atrial\u0103 asupra nodulului sinoatrial.<\/span><\/div>\n
Reflexul Bainbridge are rolul de a preveni acumularea s\u00e2ngelui \u00een vene, atrii \u015fi circula\u0163ia pulmonar\u0103. Stimularea receptorilor atriului st\u00e2ng determin\u0103 cre\u015fteri importante ale frecven\u0163ei cardiace \u015fi o cre\u015ftere a fluxului sanguin  renal (prin inhibitori elibera\u0163i de ADH) mecanism prin care se mic\u015foreaz\u0103 volumul ventricular \u015fi intravascular de r\u0103spuns la starea de imponderabilitate (c\u00e2nd s\u00e2ngele, \u00een absen\u0163a gravita\u0163iei se deplaseaz\u0103 din membrul inferior spre cap \u015fi torace).<\/span><\/div>\n
                        Baroreceptorii ventriculari  <\/span><\/div>\n
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Sunt mai pu\u0163in numero\u015fi, eviden\u0163i subendocardic \u015fi subepicardic \u00een ambii ventriculi, produc\u00e2nd efecte depresoare \u00een cazul destinderilor mari nefiziologice ale ventricului st\u00e2ng.<\/span><\/div>\n
                        Baroreceptorii pulmonari<\/span><\/div>\n
           <\/span><\/div>\n
Se g\u0103sesc \u00een adventicea trunchiului arterei pulmonare \u015fi a ramuri drepte \u015fi st\u00e2ngi ale acesteia. Sunt stimula\u0163i de distensia vaselor pulmonare \u015fi determin\u0103 vasodilata\u0163ie cu hipotensiune arterial\u0103 \u015fi bradicardie.<\/span><\/div>\n
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            Baroreceptorii mezenterici<\/span><\/div>\n
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Determin\u0103 efecte depresoare dovedite experimental prin experien\u0163a lui Goltz c\u00e2nd stimularea unei anse intestinale determin\u0103 bradicardie.<\/span><\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"

Baroreceptorii sinocarotidieni Sunt situa\u0163i deasupra carotidei primitive, pe carotida intern\u0103 se afl\u0103 o por\u0163iune dilatat\u0103 sub form\u0103 de bulb numit sinus carotidian. Sunt cei mai bine studia\u0163i deoarece sinusul carotidian poate fi izolat vascular \u015fi perfuzat f\u0103r\u0103 lezarea inerva\u0163iei locale. Aceste forma\u0163iuni receptoare sunt stimulate prin distensia transversal\u0103 (dilatare) sau longitudinal\u0103 (alungite) consecutive varia\u0163iilor presiunii […]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[1],"tags":[],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/cvnextjob.com\/index.php\/wp-json\/wp\/v2\/posts\/89319"}],"collection":[{"href":"https:\/\/cvnextjob.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/cvnextjob.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/cvnextjob.com\/index.php\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/cvnextjob.com\/index.php\/wp-json\/wp\/v2\/comments?post=89319"}],"version-history":[{"count":0,"href":"https:\/\/cvnextjob.com\/index.php\/wp-json\/wp\/v2\/posts\/89319\/revisions"}],"wp:attachment":[{"href":"https:\/\/cvnextjob.com\/index.php\/wp-json\/wp\/v2\/media?parent=89319"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/cvnextjob.com\/index.php\/wp-json\/wp\/v2\/categories?post=89319"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/cvnextjob.com\/index.php\/wp-json\/wp\/v2\/tags?post=89319"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}