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CARDIOVASCULAR PHYSIOLOGY

Circulation to Special R<-(*ions

Brain: blood (Iow normally remains constant fautoregulation). allhough regional varia(ion rełatcd to brain activity occurs. Littlc influence of autonomie nervous system. LocaJ metabolic factors most important for controlling blood (Iow (e.g. IK C0₂, Oj, and adenosine inerease blood flow).

Lungs: important to inatch perfusion to ventilation. Littlc influence of autonomie nervou$ system. Changes in O2 tension most important in regułating blood flow tdecreased Oj decreases blood flow, and incrcased Oj inereases blood flow)-

Liver and spłanchnic bods: blood flow regulati*d to facili-tate digestion. Sympathetic nen.es decrease blood flow, and parasympathetic nerves inerease blood flow. Cl hor-mones (gastrin, cholecystoki-nin, sccretin) inerease blood flow, as do products of digestion (glucose and fatty acids)

Kidneys: blood flow normally maintained constant tauto-regulation) to maintain nor mai glomerular filtration. Sympathetic nerves decrease blooci flow. Grculat-ing hormones also affect blood flow (A-ll and vaso pressin decrease blood flow: ANP inereases blood flow)

Coronary arteries: flow inter-rupted during systole. Little fluence of autonomie nervo. system. Local metabolic tac tors most important for controlling blood flow (e.g., adenosine, NO. and decreased 0_? inerease blood flow)

Skin: blood flow altered fot thermoregulation. Sympalh-etic nerves decrease blood flow (a-receptors). Circulatirc. hormones also affect blood flow. A-ll and vasoptessin de-crcase blood flow; ANP in-creases blood flow

Skclelal muscle: major determinant of total peripheral resistance. Blood flow regu-lated in response to exeirisc. Basai tlow set by sympathetic nerves. Circulating hormone' also affect flow (A-ll and vaso pressin decrease blood flow ANP inereases blood flow). Wilh exercise, release of me tabolites (e.g. H-, lactate. COj, O), adenosinei inereases blood flow

Figurę 4.17 Circulation to Spegial Regions_

Blood flow to ditterenl vas< ular beds is regulated by a number of factors and in response to the physiologic al demands of the tissues.

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