ES. Haemostasis, Haemorrhage and shock Flashcards
why is excessive blood loss a medical emergency?
decreased blood volume results in fall in blood pressure and impaired delivery of nutrients to cells which is called shock
what is the immediate physiological response to blood less?
stop the bleeding
what is short term physiological response to blood loss?
restore blood pressure
what is the medium term physiological response to blood loss?
restore fluid volume
what is the long term physiological response to blood loss?
replace blood constituents
what components are involved in an immediate response to blood loss?
vascular response
platelet response
plasma response (coagulation)
what is the vascular response of smooth muscle during blood loss?
spasm due to trauma
- myogenic response
- humoral factors (vasoconstrictors)
what is the vascular response of endothelium during blood loss?
- platelet adhesion and aggregation
- anticlotting and fibrinolysis
how do platelets respond to blood loss?
damage to blood vessels therefor turbulent blood flow
platelets come into contact with vessel wall (collagen)
what is it called when platelets adhere and clump together in response to blood loss?
aggregate
what do platelets do in positive feedback when there is blood loss?
release chemicals that cause further aggregation and form platelet plug
how is a blood clot formed?
plasma proteins and tissue components combine to convert fibrinogen to fibrin to form the blood clot
where are clotting factors formed for coagulation in blood loss?
liver
how are clotting factors synthesised and activated?
synthesised upon presence of vitamin c
activated in an enzyme cascade
what does a platelet plug do?
seals small blood vessels
what factor converts soluble fibrin to insoluble fibrin?
factor XIIIa
…….^
how do the extrinsic and intrinsic pathway need to convert factor X to factor Xa?
phospholipid and calcium ion
what is the intrinsic pathway in coagulation?
vascular damage
contact activation
factors = XII, XI, IX, VIII
what is the extrinsic pathway in coagulation?
tissue damage
(tissue factors eg. tissue thromboplastin)
factors = VII
is the intrinsic or extrinsic pathway more important in initiating blood clotting?
extrinsic
what pathway (intrinsic or extrinsic) maintains the process in coagulation?
intrinsic
what is thrombosis?
intrinsic system of coagulation where a blood clot forms inside an intact blood vessel
what is fibrinolysis?
when blood clot has saved its purpose it is dissolved
how is fibrinolysis undertaken?
by enzyme called plasmin
what converts plasminogen to plasmin?
plasminogen activator
what are the short term bodily reaction to loosing blood pressure?
- loss of blood volume/pressure
what mechanisms help to restore the blood pressure in the short term?
what triggers it?
compensatory mechanisms triggered by arterial baroreceptors
what are the medium term responses to restore blood volume in blood loss?
- shifting interstitial fluid back into blood vessels
- decreasing fluid loss in kidney
- increasing fluid intake
through baroreceptor reflexes, low arterial blood pressure has what effect on arterioles?
vasoconstriction
- increases total peripheral resistance
- decreased capillary blood pressure
through baroreceptor reflexes, low arterial blood pressure has what effect on hydrostatic pressure?
decreases it pushing fluid out of the capillary
haemorrhage causes a reduction in capillary pressure, what happens to our reabsorption/filtration when we are trying to recover?
more reabsorption than filtration
how do we decrease fluid loss in the kidney?
decrease the glomerular filtration
increase reabsorption of na and h2o
how do we increase the reabsorption of na and h20 in the kidney?
stimulate the release of renin-angiotensin- aldosterone and antidiuretic hormone
how do vasoconstrictors facilitate the process of decreasing fluid loss in the kidney?
they increase peripheral resistance
what does the presence of resin do in the kidney?
converts angiotensinogen to angiotensin I
what does angiotensin converting enzyme do in the kidney?
converts angiotensin I to angiotensin II
what structure in the kidney facilitates the release of increased aldosterone?
adrenal cortex
what does aldosterone do in the kidney?
increases sodium and water reabsorption by the distal convoluted tubes and cortical collecting ducts
what does secretion of the antidiuretic hormone do to plasma ?
reduces volume
increases osmolarity
what does antidiuretic hormone secretion do to the baroreceptors and the osmoreceptors?
decreases their effect and increases effect of osmoreceptor activation
what stimulates thirst?
increased plasma osmolarity and decreased extracellular volume
angiotensin II promotes thirst
dry mouth
what receptors in the stomach suppress drinking?
stretch receptors
in long term responses to blood loss how long does it take restore the plasma proteins?
released from the liver in 3 to 4 days
in long term responses to blood loss how long does it take to replace the blood cells?
2-3 months
how are blood cells returned to normal after blood loss?
erythropoiesis
- regulated by erythropoietin
- EPO released from kidney
stimulates RBC production in bone marrow
how is shock characterised in tissues?
inadequate blood flow to tissues
how is shock characterised in tissues?
inadequate blood flow to tissues
what is shock associated with in term of blood?
decreased cardiac output
decreased blood or ECF volume
give features of hypovolaemic shock?
decreased ECF volume due to:
haemorrhage, sweating, diarrhoea or burns
give examples of low resistance shock?
decreased peripheral resistance, due to widespread vasodilation
give an example of when lo resistance shock would occur?
anaphylactic shock
what is cardiogenic shock ?
heart fails as a pump
when would cariogenic shock occur?
heart attack
