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Endocrine System BDS1 > Haemostasis, Haemorrhage & Shock > Flashcards

Haemostasis, Haemorrhage & Shock Flashcards

1
Q

what is shock?

A

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

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2
Q

what are the main physiological responses to blood loss?

A

immediate, short term, medium term, long term

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3
Q

what is the immediate response to blood loss?

A

stop the bleeding (haemostasis)

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4
Q

what is the short term response to blood loss?

A

restore blood pressure

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5
Q

what is the medium term response to blood loss?

A

restore fluid volume

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6
Q

what is the long term response to blood loss?

A

replace blood constituents

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7
Q

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

A

vascular response, platelet response, plasma response

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8
Q

what 2 things contribute to vascular response?

A

smooth muscle and endothelium

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9
Q

how does smooth muscle contribute to vascular response?

A

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

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10
Q

how does the endothelium contribute to vascular response?

A

platelet adhesion and aggregation, anticlotting and fibrinolysis

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11
Q

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

A

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

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12
Q

how do platelets respond to blood loss?

A

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

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13
Q

how does coagulation work?

A

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

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14
Q

where are clotting factors made?

A

in the liver

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15
Q

what does the synthesis of many clotting factors require?

A

the presence of Vitamin K

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16
Q

when are the clotting factors activated?

A

in an enzyme cascade

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17
Q

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

A

one activated factor activates the next one in the sequence

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18
Q

give examples of blood clotting factors

A

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

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19
Q

what are the 3 pathways of coagultion?

A

intrinsic, extrinsic and common

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20
Q

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

A

prothrombin and fibrinogen

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21
Q

when is the intrinsic coagulation pathway used?

A

when there is vascular damage

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22
Q

what factors are activated in the intrinsic coagulation pathway?

A

12, 11, 9, 8

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23
Q

when is the extrinsic coagulation pathway used?

A

tissue damage

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24
Q

what factor is activated in the extrinsic coagulation pathway?

A

7

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25
Q

when is the extrinsic pathway more important?

A

in initiating clotting after an injury

26
Q

what does the intrinsic system do?

A

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

27
Q

what is thrombosis?

A

a blood clot forming inside an intact blood vessel

28
Q

what is fibrinolysis?

A

when the blood clot has served its purpose it is dissolved

29
Q

what enzyme breaks up fibrin?

A

plasmin

30
Q

describe the process of fibrinolysis

A

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

31
Q

what happens to blood pressure and volume in shock?

A

the loss of blood volume causes a fall in blood pressure

32
Q

what happens when blood pressure falls?

A

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

33
Q

what are baroreceptor reflexes mediated by?

A

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

34
Q

describe the process of the baroreceptor reflexes when blood volume drops

A

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

35
Q

what decreases when a haemorrhage occurs?

A

stroke volume, cardiac output, mean arterial pressure

36
Q

what remains constant when a haemorrhage occurs?

A

heart rate and total peripheral resistance

37
Q

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

A

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

38
Q

what is hydrostatic pressure?

A

blood pressure

39
Q

what is oncotic pressure?

A

plasma proteins

40
Q

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

A

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

41
Q

what does the vasoconstriction of arterioles do?

A

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

42
Q

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

A

it is about the same

43
Q

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

A

reabsorption is greater then filtration

44
Q

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

A

decreased glomerular filtration, increased reabsorption of sodium and water

45
Q

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

A

by stimulating renin-angiotensin-aldosterone and antidiuretic hormone

46
Q

what are renin-angiotensin-aldosterone and ADH?

A

vasoconstrictors

47
Q

what are the stimuli for thirst?

A

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

48
Q

what do stretch receptors in the stomach suppress?

A

feed-forward regulation

49
Q

what happens during the long term response for blood loss?

A

plasma proteins restored, blood cells replaced, erythropoiesis

50
Q

where are plasma proteins released from?

A

the liver

51
Q

what is erythropoiesis regulated by?

A

erythropoeitin

52
Q

where is erythropoeitin released from ?

A

kidney

53
Q

what does erythropoeitin do?

A

stimultes RBC production in bone marrow

54
Q

describe the action of erythropoietin

A

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

55
Q

what is shock characterised by?

A

inadequate flow to tissues

56
Q

what is shock often associated with?

A

decreased cardiac output, decreased blood or ECF volume

57
Q

what are the 3 types of shock?

A

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

58
Q

what is hypovolaemic shock?

A

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

59
Q

what is low resistance shock?

A

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

60
Q

what is cardiogenic shock?

A

heart fails as a pump

Endocrine System BDS1 (7 decks)

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