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CP-1 > Hemostasis and Clotting Cascade > Flashcards

Hemostasis and Clotting Cascade Flashcards

(48 cards)

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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?

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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?

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A

neural reflex = not necessary or sufficient

22
Q

What are the 3 major steps/goals of coagulation?

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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?

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A

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

24
Q

What generally occurs in primary hemostasis?

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A

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

25
What blood vessel properties prevent blood clots?
smooth surface - prevents platelets from rupturing | membrane proteins: glycocalyx and thrombomodulin
26
What clotting cascade proteins are Vit K dependent and are therefore inhibited by warfarin?
factors 2, 7, 9, 10 | proteins C and S
27
How does the phospholipid platform of platelets influence fibrin?
accelerates production of fibrin 100 to 1000 times
28
What does heparin do?
binds antithrombin 3 --> blocks 10a, 8a, and 2a
29
Once platelets go to the site of an injured vessel (VWF), what happens?
platelets swell --> ER releases calcium --> smooth muscle contraction --> granules leave platelet --> platelets stick to vessel wall and to each other
30
How does aspirin work?
irreversible inhibition of cyclooxygenase/COX --> inhibits platelet aggregation and prevents clot formation
31
What do platelet cell membranes contain (3)?
glycoproteins --> sticky phospholipids --> activate clotting cascade collagen receptors
32
What do you need to change plasminogen to plasmin?
Protein C has to inactivate tPA inhibitor --> then tPA can change plasminogen to plasmin
33
What is the other name for factor II? | factor IIa?
prothrombin | thrombin
34
What does HMWK collagen do?
activates factor 12 --> intrinsic pathway
35
What path does aPTT/PTT evaluate? | What are the factors tested?
intrinsic | PITT
36
What do activated protein C and S do?
inactivate factor 8a and factor 5a --> inhibits clotting cascade
37
What is the order of factors in the intrinsic path?
12 --> 11 --> 9 -->8 --> 10
38
How does warfarin work?
decreases amount of active vit K by inhibiting Vit K 2,3-epoxide reductase
39
How does ticlopidine work?
irreversibly inhibits ADP pathway involved in fibrinogen binding --> inhibits platelet aggregation and prevents clot formation
40
What is a normal PTT?
30-50 sec
41
What is the function of thrombomodulin?
blood vessel membrane protein that changes thrombin into an anticoagulant
42
What do platelets contain within their cytoplasm? (7)
``` actin and myosin mitochondria remnants of ER cyclooxygenase, thromboxane A2 fibrin stabilizing factor growth factors serotonin ```
43
What things can be released from endothelial cells to prevent clotting?
prostacyclin and NO --> prevents platelet activation and causes vasodilation heparin --> binds antithrombin 3 --> will block 10a, 8a, and 2a
44
What is hemophilia B?
factor 9 deficiency
45
What defines hemostasis?
the steps taken by the body to limit blood loss | not just confined to the production of a blood clot!
46
What activates kallikrein?
factor 12a | prekallikrein --> kallikrein
47
How is vitamin K used in synthesizing certain clotting factors?
Vit K needed to form carboxyglutamate residues that can chelate Ca
48
What is the Leiden mutation?
mutation in factor V so that protein C cannot deactivate it --> have too much clotting

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