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Pathology and Immunity > Haemostasis, Haemorrhage and Shock > Flashcards

Haemostasis, Haemorrhage and Shock Flashcards

1
Q

what does excessive blood loss lead to

A

fall in blood pressure
impaired delivery of nutrients to cells

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2
Q

what is shock

A

this is when blood pressure and nutrient delivery decreases due to an excessive loss of blood

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3
Q

what are the physiological responses to blood loss

A

immediate
short term
medium term
long term

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4
Q

describe the immediate response to blood loss

A

stopping the bleeding

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5
Q

what is the short term response to blood loss

A

restore the blood pressure

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6
Q

what is the medium term physiological response to blood loss

A

restore fluid volume

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7
Q

what is the long term response to blood loss

A

replace blood constituents

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8
Q

what are the components of haemostasis

A

vascular response
platelet response
plasma response - coagulation

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9
Q

describe what happens to smooth muscle in haemostasis

A

spasms due to trauma, myogenic response and humoral factors (vasoconstrictors)

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10
Q

describe what happens to endothelium during haemostasis

A

platelet adhesion and aggregation
anticlotting and fibrinolysis

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11
Q

describe the process of platelet response

A
  • damage to blood vessel
  • turbulent blood flow
  • platelets come into contact with vessel wall
  • platelets adhere and clump together
  • release chemicals that cause further aggregation
  • formation of platelet plug
  • effective in sealing small blood vessels
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12
Q

describe the role of thromboxane A2 in forming platelet plugs

A

vasoconstriction

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13
Q

describe the role of ADP in platelet plug formation

A

involved in aggregation and release chemicals in platelets

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14
Q

where are most clotting factors synthesised

A

liver

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15
Q

what is used for synthesising most clotting factors

A

vitamin K

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16
Q

why do platelets only aggregate in veins that are unhealthy

A

the increased turbulence caused by trauma allows for them to touch the walls, and then the collagen in the walls allow for adhesion

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17
Q

describe the whole platelet plug formation

A
  • damaged blood vessels allow aggregation of platelets
  • these platelets release ADP and thromboxane to act on the aggregation and increase it
  • vasoconstriction facilitates the sealing of blood vessels, and this is done through the thromboxane
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18
Q

how are clotting factors in the blood activated

A

through an enzyme cascade

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19
Q

describe the common pathway for coagulation

A
  • fibrinogen is converted to soluble fibrin
  • by thrombin
  • thrombin comes from prothrombin, conversion uses factor Xa, calcium, factor V and phospholipids
  • soluble fibrin is converted to insoluble fibrin by a cascade that is created by thrombin converting factor
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20
Q

what is used to convert prothrombin to thrombin

A

factor Xa
factor V
phospholipids
calcium

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21
Q

how many different blood clotting factors are there

A

13 (technically 12 as 6 does not exist)

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22
Q

what is factor I

A

fibrinogen

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23
Q

what is factor II

A

prothrombin

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24
Q

what is factor III

A

tissue factor thromboplastin

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25
Q

what is factor IV

A

calcium ions

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26
Q

what is factor V

A

proaccelerin

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27
Q

what is factor VII

A

proconvertin

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28
Q

what is factor VIII

A

antihaemophilic globulin

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29
Q

what is factor IX

A

christmas factor

30
Q

what is factor X

A

stuart prower factor

31
Q

what is factor XI

A

plasma thromboplastin antecedent

32
Q

what is factor XII

A

hageman factor

33
Q

what is factor XIII

A

laki lorand factor

34
Q

which blood clotting factors are associated with well known genetic conditions

A

factors 9 and 10

35
Q

what are the two pathways that can activate factor 10

A

intrinsic and extrinsic

36
Q

describe the intrinsic pathway to activating factor 10

A

vascular damage leads to contact activation involving factors XII, XI, IX, VIII, calcium ions and phospholipids

37
Q

describe the extrinsic pathway to activating factor 10

A

tissue damage, tissue factor tisssue thromboplastin and factor VII, phospholipids and calcium ions are used as well

38
Q

which pathway is more important for initiating a clot after injury

A

the extrinsic pathway

39
Q

which pathway maintains the clot production after initiation

A

the intrinsic pathway

40
Q

what is thrombosis

A

this is when a clot forms in a vessel that has not been injured, and is usually associated with the intrinsic coagulation pathway

41
Q

what is fibrinolysis

A

this is when a blood clot is dissolved after it has served its purpose

42
Q

which enzymes undertakes fibrinolysis

A

plasmin

43
Q

describe how fibrinolysis occurs

A

plasminogen is converted to plasmin via the plasminogin activator
plasma acts on fibrin to produce soluble fibrin fragments

44
Q

describe the short term impacts on blood pressure

A

loss of blood volume leads to a fall in blood pressure
there are compensentory mechanisms triggered by the arterial baroreceptors, and these mechanisms aim to resotre the blood pressure

45
Q

what mediates the baroreceptor reflexes

A

sympathetic nerves

46
Q

which hormones are involved in restoring blood pressure after loss of blood volume

A

adrenaline
angiotensin II
vasopressin

47
Q

which hormone is vasopressin

A

ADH

48
Q

describe how a decrease in blood pressure from a decrease in blood volume is restored through baroreceptor reflexes

A
  • decreased BP leads to decreased baroreceptor firing
  • this goes to the CVS centres in the brainstem
  • this increases sympathetic nervous system activity
  • this increases heart rate, ventricular contraction, venous constriction, and arterial contration
  • increased venous constriction and venous contraction increases stroke volume, which increases cardiac output
  • increases arteriol constriction leads to increased peripheral resistance
  • increased peripheral resistance and cardiac output increases the mean arterial blood pressure overall
49
Q

what are the positive reflex compensations after haemorrhage

A

heart rate and total peripheral resistance

50
Q

what are the negative reflex compensations after haemorrhage

A

stroke volume
cardiac output
mean arterial pressure

51
Q

describe the medium term responses to restore blood volume

A
  • interstitial fluid is shifted back into blood vessels
  • there is decreased fluid loss in the kidneys
  • increased fluid intake
52
Q

describe how hydrostatic pressure is at the point where arterioles become capillaries through to the venule

A

35mmHg, to 15mmHg at the end

53
Q

describe the oncotic pressure in capillaries

A

25mmHg

54
Q

what does decreased arterial blood pressure cause through the baroreceptor reflexes

A
  • arterioles will vasoconstrict to decrease the hydrostatic pressure that pushes fluid out of the capillary
  • this means there is more fluid being drawn back into the capillaries by oncotic pressure
55
Q

what does vasoconstriction of arterioles lead to

A

an increase in total peripheral resistance
a decrease in capillary blood pressure

56
Q

describe how hydrostatic pressure is in the capillary during haemorrhage

A

at arteriole it is 25mmHg instead of 35, and at the venule it is 10mmHg instead of 15mmHg

57
Q

does oncotic pressure change when there is haemorrhage

A

no it remains around 25mmHg

58
Q

describe what happens in the kidney when there is decreased blood volume

A

there is less fluid loss in the kidney to increase the blood volume
- done by a decrease in glomerular filtration
- increase in reabsorption of sodium and water by stimulating the release of RAAS and antidiuretic hormone

59
Q

does aldosterone release increase or decrease in response to a decreased blood volume

A

increases to increase reabsorption of sodium and water

60
Q

describe the pathway of ADH release during decreased blood volume

A

decreased plasma volume causes a decrease in baroreceptor distension, releasing ADH from posterior pituitary
increased plasma osmorality increases the osmoreceptor activation, increasing ADH release from posterior pituitary
this increases the water permeability of collecting ducts in the kidney

61
Q

describe thirst and how it happens

A

this is a desire to drink, and is controlled by the hypothalamus

62
Q

what is the stimulus for feeling thirst

A

an increase in plasma osmorality and a decreased in extracellular fluid volume
angiotension II can promote thirst
dry mouth

63
Q

what is feed forward regulation

A

this is when stretch receptors in the stomach suppress drinking

64
Q

describe long term responses to a decreased blood volume

A

restored plasma proteins are released from the liver in 3-4 days
red blood cells are replaced
erythropoiesis occurs

65
Q

describe erythropoiesis

A
  • regulated by erythropoietin released from the kidney
  • stimulates red blood cell production in bone marrow
  • returns to normal in 2-3 months
66
Q

describe the steps to erythropoiesis

A
  • decreased red blood cell numbers
  • decreased oxygen delivery
  • kidney detects
  • releases erythropoietin
  • travels to red bone marrow
  • increase in red blood cell production
67
Q

what is shock characterised by

A

inadequate blood flow to tissues that is associated with decreased cardiac output and a decreased in blood/ECF volume

68
Q

which shock can be fatal

A

irreversible

69
Q

what are the three main types of shock

A

hypovolemic
low resistance shock
cardiogenic shock

70
Q

describe hypovolemic shock

A

decreased ECF volume due to:
haemorrhage, sweating, diarrhoea, burns, cholera and ebola

71
Q

describe low resistance shock

A

aka distributive shock
decreased peripheral resistance due to widespread vasodilation
that occurs in anaphyalxis

72
Q

describe cardiogenic shock

A

this is when the heart fails to pump, and is a typical form of shock

Pathology and Immunity (16 decks)

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