Flashcards in Lecture 25: Hemorrhage Deck (16):
when 30-40% of blood volume is lost, cannot save animal from failure if transfusion is given too late. Assoc. with sudden withdrawal of sympathetic drive ("decompensation")
Arterial baroreflex to compensate for hemorrhage
rapid peripheral vasoconstriction via sympathetic drive triggered by low BP and unloading of baroreceptors. The most rapid compensatory mech.!
Which areas are vasoconstricted first in Arterial baroreflex?
non-vital vascular beds (skeletal, spleen, cutaneous, hepatic)
Chemoreflex compensatory mech. for hemorrhage
elicits increased vasoconstriction and hyperventilation. Stimulated by low O2 in blood due to low blood flow
Cerebral Ischemia compensatory mech. for hemorrhage
activates sympathoadrenal system for vasoconstriction. Prolonged activation may result in strong vagal stimulation and bradycardia
Reabsorption of Tissue fluids to compensate for hemorrhage
decreased capillary hydrostatic pressure promotes reabsorption of fluid. Cortisol increases capillary permeability to help this process
Endogenous vasoconstrictors compensatory mech. for hemorrhage
Increases circulating levels of E and NE
2 methods of renal conservation of water and salt in hemorrhage
1) vasopressin/ADH --> vasoconstrictor, promotes water reabsorption
2) angiotensin II --> vasoconstrictor, triggers release of more ADH
Aldosterone stimulated by
stimulates sodium reabsorption by the renal tubules
what causes decrease in hematocrit?
increase in fluid volume relative to red blood cell concentration
long term mechs. to increase blood volume: (2)
1) increased aldosterone release and decreased Na excretion
2) increased lvls of Ang II to stimulate thirst and salt appetite
final compensation for hemorrhage
restoration of lost plasma proteins and blood cells
where are plasma proteins and blood cells synthesized?
liver, bone marrow. proteins take few days, RBCs take 2-3 weeks
quick acting method of restoring volume post hemorrhage?
reabsorption of interstitial fluid back into capillaries