Haemostasis, Haemorrhage & Shock

Question 1

what is shock?

Answer 1

decreased blood volume resulting in fallen blood pressure and impaired delivery of nutrients to cells

Question 2

what are the main physiological responses to blood loss?

Answer 2

immediate, short term, medium term, long term

Question 3

what is the immediate response to blood loss?

Answer 3

stop the bleeding (haemostasis)

Question 4

what is the short term response to blood loss?

Answer 4

restore blood pressure

Question 5

what is the medium term response to blood loss?

Answer 5

restore fluid volume

Question 6

what is the long term response to blood loss?

Answer 6

replace blood constituents

Question 7

what components are involved in the immediate response to blood loss?

Answer 7

vascular response, platelet response, plasma response

Question 8

what 2 things contribute to vascular response?

Answer 8

smooth muscle and endothelium

Question 9

how does smooth muscle contribute to vascular response?

Answer 9

spasm due to trauma and has a myogenic response and humoral factors (vasoconstrictors)

Question 10

how does the endothelium contribute to vascular response?

Answer 10

platelet adhesion and aggregation, anticlotting and fibrinolysis

Question 11

what are the events leading up to platelet response to blood loss?

Answer 11

damage to blood vessel - turbulent blood flow - platelets come into contact with vessel wall (collagen)

Question 12

how do platelets respond to blood loss?

Answer 12

platelets adhere (clump together), release chemicals that cause further aggregation, formation of platelet plug, effective in sealing small blood vessels

Question 13

how does coagulation work?

Answer 13

various plasma proteins and tissue components combine to convert fibrinogen to fibrin to form the blood clot

Question 14

where are clotting factors made?

Answer 14

in the liver

Question 15

what does the synthesis of many clotting factors require?

Answer 15

the presence of Vitamin K

Question 16

when are the clotting factors activated?

Answer 16

in an enzyme cascade

Question 17

what does it mean when factors are activated in a cascade?

Answer 17

one activated factor activates the next one in the sequence

Question 18

give examples of blood clotting factors

Answer 18

1 - fibrinogen, 2 - prothrombin, 3- tissue factor, 4 - calcium ions, 5 - proaccelerin, 7 - proconvertin, 8 - antihaemophilic globulin, 9 - christmas factor, 10 - stuart-prower factor, 11 - plasma thromboplastin antecedent, 12 - hageman factor, 13 - laki-lorand factor

Question 19

what are the 3 pathways of coagultion?

Answer 19

intrinsic, extrinsic and common

Question 20

what 2 clotting factors are involved in the common pathway of coagulation?

Answer 20

prothrombin and fibrinogen

Question 21

when is the intrinsic coagulation pathway used?

Answer 21

when there is vascular damage

Question 22

what factors are activated in the intrinsic coagulation pathway?

Answer 22

12, 11, 9, 8

Question 23

when is the extrinsic coagulation pathway used?

Answer 23

tissue damage

Question 24

what factor is activated in the extrinsic coagulation pathway?

Answer 24

7

Question 25

when is the extrinsic pathway more important?

Answer 25

in initiating clotting after an injury

Question 26

what does the intrinsic system do?

Answer 26

serves to maintain the process once it has started and may have a role in events such as thrombosis

Question 27

what is thrombosis?

Answer 27

a blood clot forming inside an intact blood vessel

Question 28

what is fibrinolysis?

Answer 28

when the blood clot has served its purpose it is dissolved

Question 29

what enzyme breaks up fibrin?

Answer 29

plasmin

Question 30

describe the process of fibrinolysis

Answer 30

plasminogen activator activates plasminogen which is converted to plasmin, plasmin breaks down fibrin to give soluble fibrin fragments

Question 31

what happens to blood pressure and volume in shock?

Answer 31

the loss of blood volume causes a fall in blood pressure

Question 32

what happens when blood pressure falls?

Answer 32

compensatory mechanisms are triggered by the arterial baroreceptors, these mechanisms aim to restore the blood pressure

Question 33

what are baroreceptor reflexes mediated by?

Answer 33

sympathetic nerves and hormones: adrenaline, angiotensin II and vasopressin (ADH)

Question 34

describe the process of the baroreceptor reflexes when blood volume drops

Answer 34

decreased blood volume - decreased BP - detected by CVS centres (brainstem) - increased sympathetic NS activity - increased heart rate, ventricle contractions etc. - increased cardiac output and increased peripheral resistance - increased mean arterial blood pressure

Question 35

what decreases when a haemorrhage occurs?

Answer 35

stroke volume, cardiac output, mean arterial pressure

Question 36

what remains constant when a haemorrhage occurs?

Answer 36

heart rate and total peripheral resistance

Question 37

how is blood volume restored in the medium term response to blood loss?

Answer 37

shifting interstitial fluid back into blood vessels, decreasing fluid loss in kidney, increasing fluid intake

Question 38

what is hydrostatic pressure?

Answer 38

blood pressure

Question 39

what is oncotic pressure?

Answer 39

plasma proteins

Question 40

what does the decreased arterial blood pressure due to baroreceptor reflexes cause?

Answer 40

vasocontriction of arterioles, increased total peripheral resistance and decreased capillary blood pressure

Question 41

what does the vasoconstriction of arterioles do?

Answer 41

decreased the hydrostatic pressure pushing fluid out of the capillary, more fluid is then drawn back into the capillary by the oncotic pressure

Question 42

in normal BP what is the ratio of filtration to reabsorption in the capillary

Answer 42

it is about the same

Question 43

in haemorrhage, what is the ratio of reabsorption to filtration in the capillary?

Answer 43

reabsorption is greater then filtration

Question 44

what happens when there is decreased fluid loss in the kidney?

Answer 44

decreased glomerular filtration, increased reabsorption of sodium and water

Question 45

how is the reabsorption of sodium and water in the kidney increased?

Answer 45

by stimulating renin-angiotensin-aldosterone and antidiuretic hormone

Question 46

what are renin-angiotensin-aldosterone and ADH?

Answer 46

vasoconstrictors

Question 47

what are the stimuli for thirst?

Answer 47

increased plasma osmolarity, decreased ECF volume, angiotensin II, dry mouth

Question 48

what do stretch receptors in the stomach suppress?

Answer 48

feed-forward regulation

Question 49

what happens during the long term response for blood loss?

Answer 49

plasma proteins restored, blood cells replaced, erythropoiesis

Question 50

where are plasma proteins released from?

Answer 50

the liver

Question 51

what is erythropoiesis regulated by?

Answer 51

erythropoeitin

Question 52

where is erythropoeitin released from ?

Answer 52

kidney

Question 53

what does erythropoeitin do?

Answer 53

stimultes RBC production in bone marrow

Question 54

describe the action of erythropoietin

Answer 54

decreased RBC numbers - decreased O2 delivery - kidney - erythropoietin - red bone marrow - increased RBC production

Question 55

what is shock characterised by?

Answer 55

inadequate flow to tissues

Question 56

what is shock often associated with?

Answer 56

decreased cardiac output, decreased blood or ECF volume

Question 57

what are the 3 types of shock?

Answer 57

hypovolaemic shock, low resistance (or distributive) shock, cardiogenic shock

Question 58

what is hypovolaemic shock?

Answer 58

decreased ECF volume due to haemorrhage, sweating, diarrhoea, burns

Question 59

what is low resistance shock?

Answer 59

decreased peripheral resistance due to widespread vasodilation e.g. anaphylactic shock

Question 60

what is cardiogenic shock?

Answer 60

heart fails as a pump