Lecture 5: Blood Clotting Flashcards Preview

PSL301 > Lecture 5: Blood Clotting > Flashcards

Flashcards in Lecture 5: Blood Clotting Deck (89):
1

What gives rise to platelets?

megakaryocytes

2

___ are needed for blood clotting

platelets

3

How do megakaryocytes give rise to platelets?

Edges of megakaryocyte break off to form platelets (cell fragments)

4

Megakaryocytes are...

giant cells with many copies of DNA in the nucleus

5

Half life of platelets?

10 days

6

____ increases platelet numbers by...

thrombopoietin
stimulating production of platelets

7

How is blood clotting regulated? (3 phases)

1. vascular phase
2. platelet phase
3. coagulation phase

8

Vascular phase

Exposed collagen & tissue factors cause vasoconstriction of the damaged blood vessel. Vasoconstriction minimizes blood loss.

9

Vascular phase controlled by...

nervous system & muscles (neurogenic & myogenic control)

10

Vasoconstriction in vascular phase prolonged by...

1. Serotonin
2. Endothelin-1
3. Thromoboxane A2

11

Platelet phase

1. Collagen exposed to blood stream; bind platelets passing by in the blood
2. Factors released from trapped platelets attract more platelets
3. Platelets aggregate to form plug

12

What makes von Willebrand factor?

endothelial cells
platelets

13

What does von Willebrand factor bind to?

collagen
platelets

14

What are the factors released from platelets?

ADP
PAF (platelet activating factor)
serotonin
thromboxane

15

When are factors released from platelets?

during platelet phase

16

What does serotonin and thromboxane cause?

vasoconstriction

17

What do activated platelets look like?

spiky outer surface

18

Purpose of activating platelets?

they can adhere to each other better

19

What do inactivated platelets look like?

disk-like cell fragments

20

What prevents platelet adhesion/activation during normal situations?

Vasodilators:
NO
Prostacyclin

21

What releases NO and prostacyclin

endothelium

22

Prostacyclin is made up of...

Prostaglandin I2, PGI2

23

Why is aspirin given after mild heart attacks?

Precursor for thromboxane is arachidonic acid.
Enzyme cyclooxygenase cleaves ADA -> PGH2 -> thromboxane.
Aspirin stops CO activity, so thromboxane can't be made.
Since thromboxane is used to vasoconstrict & aggregate platelets, these don't happen as easily.

24

Function of von Willebrand factor?

- link platelet with collagen
- draw platelet into exposed collagen area
- keep VII in circulation longer

25

What happens during vascular phase?

vasoconstriction

26

What happens during platelet phase?

Platelets are actively trying to stop bleeding (loose platelet plug)

27

What happens during coagulation phase?

- Proper blood clot forms via coagulation cascade
- Fibrinogen -> fibrin

28

Fibrin

Long strand of fibre that reinforces loose platelet plug

One piece of fibrinogen

29

Inactive form of fibrin

fibrinogen

30

What do all the factors released from platelets cause?

platelet aggregation

31

What are the effects of thromboxane?

Constriction
Platelet aggregation

32

Cyclooxygenase catalyses what reaction?

arachidonic acid -> PGH2

33

What can PGH2 become?

Prostaglandins
Thromboxane
Prostacyclin

34

Why is prostacyclin activity not affected when aspirin is taken?

Endothelial cells can still make more CO

35

What is the sturdiest form of fibrin?

covalent cross-links

36

What enzyme cleaves fibrinogen to fibrin?

thrombin

37

is fibrin soluble / insoluble?

insoluble

38

How does fibrin become cross-linked?

Factor XIII & Ca++ catalysed

39

Summary of coagulation cascade

1. Contact activation pathway
2. Tissue factor pathway
3. Common pathway

1->3 or 2->3

40

Intrinsic pathway

Contact activation pathway

41

extrinsic pathway

tissue factor pathway

42

trigger for intrinsic pathway

collagen in bld vessels exposed due to injury

43

What is the function of ADP?

Attract more platelets to damaged area

44

Trigger for extrinsic pathway

Damaged tissue exposes thromboplastin

45

What does factor XI and factor VII activate?

Factor X (common pathway)

46

What activates prothrombin activator?

Factor X
Factor III
Factor V
Ca++
PF3
PL

47

Purpose of prothrombin activator?

prothrombin -> thrombin

48

What activates factor XIII?

Thrombin

49

What is the beginning of the common pathway?

active factor X

50

Where are many plasma factors used for blood clotting made?

liver

51

Cascade of intrinsic pathway

1. Exposed collagen activates factor XII
2. Factor XII & Ca++ activate Factor XI
3. Factor XI & Ca++ activate factor IX
4. Factor IX, factor VIII, Ca++, PL activate factor X

52

what regulates levels of factor VIII?

von Willebrand factor (keeps VIII around for longer)

53

Vit K needed for the synthesis of...

thrombin
VII
IX
X

54

What drugs blocks the action of vit K?

Coumadin / Warfarin
-> less blood clotting

55

What vitamin helps blood clotting?

vit K

56

Cascade of extrinsic pathway

1. Factor III from thromboplastin activate Factor VII
2. VII + III activate IX
3. III and VII // Ca++ // PL -> activates X

Positive feedback:
X activates VII

57

vWf disease (symptoms)

problem with quality or quantity of vWf
problem with blood clotting

58

Which areas are most affected by the lack of vWf?

areas w/ small number of capillaries (skin, GI, uterus)

59

treatment for vWf disease?

protein that releases vasopressin to endothelial cells: stimulate release of vWf

60

Hemophilia A need to be injected with...

VIII

61

Hemophilia B due to deficiency in...

IX

62

Symptoms of hemophilia

internal and external bleeding that doesn't stop easily

63

which pathway is still active in those with haemophilia?

Extrinsic, but not enough to have normal blood clotting efficiency

64

Purpose of plasmin

fibrin -> fibrin fragments (easy to break up and remove)

65

Which enzymes are responsible for the formation of plasminogen -> plasmin?

Thrombin
tPA

66

What enzymes are used for fibrinolysis (anticoagulants)?

1. plasmin
2. tPa
3. TFPI
4. Antithrombin
5. Protein C

67

tPA released by...

damaged endothelium (released very slowly)

68

precursor of plasmin

plasminogen

69

Thrombin has positive feedback on...

1. VII activation
2. VIII activation
3. IX activation
4. XI activation
5. V activation

70

What activates protein C?

thrombin -> (catalysed by protein S)

71

function of protein C?

1. stop activation of VIII
2. stop activation of V

72

function of TFPI?

stop VII activation

73

function of antithrombin?

1. stop IX activation
2. stop X activation
3. stop XI activation
4. stop XII activation
5. stop thrombin

74

TFPI

tissue factor pathway inhibitor

75

Where is plasminogen / plasmin released from?

liver

76

Where is tPA released from?

many tissues

77

Where is TFPI released from?

endothelium

78

Where is antithrombin released from?

liver

79

Where is protein c released from?

liver

80

tPA is activated by...

not activated

81

TFPI is activated by...

not activated

82

Antithrombin is activated by...

heparin

83

Haemorrhagic stroke

Blood vessel in brain bursts, and blood leaks into brain

84

Stroke

Blood clot gets stuck in artery going into brain

85

Thrombus

blood clot attached to vessel wall (less O gets to tissues)

86

Embolus

Floating blood clot

87

tPA

tissue plasminogen activator

88

What is a treatment for stroke?

tPA given within 3-4 after a stroke
this breaks down the blood clot

89

When is tPA not administered as a treatment for a stroke?

Haemorrhagic stroke
Will make the bleeding worse