Lecture 25: Hemorrhage

Question 0

Arterial baroreflex to compensate for hemorrhage

Answer 0

rapid peripheral vasoconstriction via sympathetic drive triggered by low BP and unloading of baroreceptors. The most rapid compensatory mech.!

Question 1

hemorrhagic shock

Answer 1

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”)

Question 2

Which areas are vasoconstricted first in Arterial baroreflex?

Answer 2

non-vital vascular beds (skeletal, spleen, cutaneous, hepatic)

Question 3

Chemoreflex compensatory mech. for hemorrhage

Answer 3

elicits increased vasoconstriction and hyperventilation. Stimulated by low O2 in blood due to low blood flow

Question 4

Cerebral Ischemia compensatory mech. for hemorrhage

Answer 4

activates sympathoadrenal system for vasoconstriction. Prolonged activation may result in strong vagal stimulation and bradycardia

Question 5

Reabsorption of Tissue fluids to compensate for hemorrhage

Answer 5

decreased capillary hydrostatic pressure promotes reabsorption of fluid. Cortisol increases capillary permeability to help this process

Question 6

Endogenous vasoconstrictors compensatory mech. for hemorrhage

Answer 6

Increases circulating levels of E and NE

Question 7

2 methods of renal conservation of water and salt in hemorrhage

Answer 7

1) vasopressin/ADH –> vasoconstrictor, promotes water reabsorption
2) angiotensin II –> vasoconstrictor, triggers release of more ADH

Question 8

Aldosterone stimulated by

Answer 8

Ang II

Question 9

Aldosterone fx

Answer 9

stimulates sodium reabsorption by the renal tubules

Question 10

what causes decrease in hematocrit?

Answer 10

increase in fluid volume relative to red blood cell concentration

Question 11

long term mechs. to increase blood volume: (2)

Answer 11

1) increased aldosterone release and decreased Na excretion

2) increased lvls of Ang II to stimulate thirst and salt appetite

Question 12

final compensation for hemorrhage

Answer 12

restoration of lost plasma proteins and blood cells

Question 13

where are plasma proteins and blood cells synthesized?

Answer 13

liver, bone marrow. proteins take few days, RBCs take 2-3 weeks

Question 14

quick acting method of restoring volume post hemorrhage?

Answer 14

reabsorption of interstitial fluid back into capillaries

Question 15

circulatory shock/hemorrhagic decompensation

Answer 15

progressive deterioration of CV function following extensive blood loss