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CP-1 > Hemostasis and Clotting Cascade > Flashcards

Hemostasis and Clotting Cascade Flashcards

1
Q

In clot removal, what does thrombin do?

A

activates protein C

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2
Q

What is INR?

A

international normalized ratio
ratio of pt’s PT to a normal sample, raised to the power of the ISI
0.94-1.4 for more sensitive and 2-3 for less sensitive thromboplastin preparations

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3
Q

What are the 4 general steps of hemostasis?

A

vascular spasm
formation of platelet plug
blood clot formation (coagulation)
repair of damage

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4
Q

What is the function of glycocalyx?

A

blood vessel membrane protein that repels platelets

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5
Q

What happens in protein C deficiency?

A

significantly increased risk of venous thrombosis

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6
Q

What is contained in the granules that platelets release?

A

ADP, thromboxane A2, and serotonin

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7
Q

What is tenase?

A

complex of 9a, 8a, Ca, and phopholipid surface

in intrinsic path

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8
Q

What form of warfarin is more active?

what enzyme is it metabolized by?

A

S-warfarin more active than R-warfarin

metabolized by cytochrome P2C9

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9
Q

What are the 2 primary causes of vascular spasm?

A 
myogenic = direct reflex response to injury, no neurons
platelet factors = serotonin and thromboxane A2 released --> vasoconstrictors
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10
Q

What is hemophilia A?

A

factor 8 deficiency –> intrinsic path inhibited
usually passed down, but 1/3 of cases are caused by a spontaneous mutation
4x more common than hemophilia B

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11
Q

What is a normal PT?

A

12-13 sec

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12
Q

How is the production of platelets controlled?

A

TPO continually secreted –> platelets have mpl receptor –> internalize and destroy TPO –> lowers amount of free TPO
NEGATIVE FEEDBACK loop

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13
Q

What are the 5 major functions of thrombin in the clot cascade?

A
  1. activates factors 5 and 8
  2. helps convert fibrinogen to fibrin
  3. activates platelets
  4. helps convert more prothrombin to thrombin
  5. activates factor 13 to cross link fibrin
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14
Q

What are the 2 enzymes needed, in order, to activate vitamin K?

A

vitamin K 2,3-epoxide reductase

quinone reductase

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15
Q

What is thrombin’s role in the intrinsic pathway of clotting cascade?

A

activates factor 8

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16
Q

How is a platelet plug formed initially (step 1)?

A

collagen exposed in damaged vessel wall –> von willebrand factor from plasma binds collagen –> platelets bind to VWF

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17
Q

What happens if you have a mutation in the TPO receptor on platelets?

A

polycythemia vera

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18
Q

What conditions might cause prolonged PT but normal PTT?

A

liver disease, decreased vit K, warfarin therapy, defective factor 7

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19
Q

What is tissue factor 3/ thromboplastin?

A

produced by endothelial cells when they are injured –> interacts with factor 7 to make factor 7a which initiates the extrinsic pathway

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20
Q

What does platelet-derived growth factor do?

A

promotes blood vessel growth and repair by stimulating fibroblasts to secrete stuff and differentiate into smooth muscle –> collagen deposition

21
Q

What is the contributing factor to vascular spasm?

A

neural reflex = not necessary or sufficient

22
Q

What are the 3 major steps/goals of coagulation?

A
  1. activation of thrombin activator
  2. activation of thrombin
  3. creation of fibrin from fibrinogen
23
Q

What is the key difference btw primary and secondary hemostastis?

A

secondary makes platelet plug strong by generating a fibrin mesh on it

24
Q

What generally occurs in primary hemostasis?

A

vasoconstriction –> platelet plug –> act as a phospholipid platform to initiate coagulation cascade

25
Q

What blood vessel properties prevent blood clots?

A

smooth surface - prevents platelets from rupturing

membrane proteins: glycocalyx and thrombomodulin

26
Q

What clotting cascade proteins are Vit K dependent and are therefore inhibited by warfarin?

A

factors 2, 7, 9, 10

proteins C and S

27
Q

How does the phospholipid platform of platelets influence fibrin?

A

accelerates production of fibrin 100 to 1000 times

28
Q

What does heparin do?

A

binds antithrombin 3 –> blocks 10a, 8a, and 2a

29
Q

Once platelets go to the site of an injured vessel (VWF), what happens?

A

platelets swell –> ER releases calcium –> smooth muscle contraction –> granules leave platelet –> platelets stick to vessel wall and to each other

30
Q

How does aspirin work?

A

irreversible inhibition of cyclooxygenase/COX –> inhibits platelet aggregation and prevents clot formation

31
Q

What do platelet cell membranes contain (3)?

A

glycoproteins –> sticky
phospholipids –> activate clotting cascade
collagen receptors

32
Q

What do you need to change plasminogen to plasmin?

A

Protein C has to inactivate tPA inhibitor –> then tPA can change plasminogen to plasmin

33
Q

What is the other name for factor II?

factor IIa?

A

prothrombin

thrombin

34
Q

What does HMWK collagen do?

A

activates factor 12 –> intrinsic pathway

35
Q

What path does aPTT/PTT evaluate?

What are the factors tested?

A

intrinsic

PITT

36
Q

What do activated protein C and S do?

A

inactivate factor 8a and factor 5a –> inhibits clotting cascade

37
Q

What is the order of factors in the intrinsic path?

A

12 –> 11 –> 9 –>8 –> 10

38
Q

How does warfarin work?

A

decreases amount of active vit K by inhibiting Vit K 2,3-epoxide reductase

39
Q

How does ticlopidine work?

A

irreversibly inhibits ADP pathway involved in fibrinogen binding –> inhibits platelet aggregation and prevents clot formation

40
Q

What is a normal PTT?

A

30-50 sec

41
Q

What is the function of thrombomodulin?

A

blood vessel membrane protein that changes thrombin into an anticoagulant

42
Q

What do platelets contain within their cytoplasm? (7)

A 
actin and myosin
mitochondria
remnants of ER
cyclooxygenase, thromboxane A2
fibrin stabilizing factor
growth factors
serotonin
43
Q

What things can be released from endothelial cells to prevent clotting?

A

prostacyclin and NO –> prevents platelet activation and causes vasodilation
heparin –> binds antithrombin 3 –> will block 10a, 8a, and 2a

44
Q

What is hemophilia B?

A

factor 9 deficiency

45
Q

What defines hemostasis?

A

the steps taken by the body to limit blood loss

not just confined to the production of a blood clot!

46
Q

What activates kallikrein?

A

factor 12a

prekallikrein –> kallikrein

47
Q

How is vitamin K used in synthesizing certain clotting factors?

A

Vit K needed to form carboxyglutamate residues that can chelate Ca

48
Q

What is the Leiden mutation?

A

mutation in factor V so that protein C cannot deactivate it –> have too much clotting

CP-1 (32 decks)

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