Coagulation

Question 1

What is the main function of vascular system in coagulation

Answer 1

Constriction of vasculature serves to reduce blood flow at the site of injury to prevent blood loss
- Vasoconstriction slows the flow of platelets passing by the injury, allowing them to have a better chance of ahering

Question 2

What is the main function of the Platelet system in coagulation

Answer 2

Act to prevent blood loss by forming platelets plugs at the injury site.

• platelets also release factors that can induce vasoconstriction
• platelets also secrete factor V and providing phospholipids needed by coagulation factors

Question 3

what is the main function of the coagulation system

Answer 3

to form fibrin clots and to further stimulate platelet activation by producing thrombin

Question 4

What is the main function of the anti-coagulation system in coagulation

Answer 4

to reduce coagulation by reducing thrombin formation and destroying thrombin that is already formed

Question 5

What is the main function of fibrinolysis system in coagulation

Answer 5

to dissolve unnecessary clots formed in undamaged tissues and to remove clots after the injury has healed

Question 6

What are the Three glycoprotein ligands and what do they bind

Answer 6

GPIb-alpha binds Willebrand factor on ECM
- Initial tether of platelets
GPVI binds collagen
- Initial activation of platelets (release platelet activators)
CPIIa/IIIb binds fibrinogen
- facilitates platelet-platelet interactions

Question 7

What are the three G protein coupled receptor ligands and what do they bind

Answer 7

P2Y12 activated by ADP

Protease activated receptor (PAR) activated by Thrombin

Thromboxan A2 receptor activated by thromboxan A2

Question 8

What are the functions of platelet secreted ADP, Serotonin and thromboxane A2

Answer 8

ADP = further activates platelets
Serotonin = further activate platelets and the cause vasoconstriction
Thromboxane A2 = activate platelets and cause vasoconstriction

Question 9

What is the function of Prostacyclin (PFI2)

Answer 9

It is formed and released by vascular endothelial cells and functions to INDUCE vasodilation and INHIBIT platelet adhesion and activation

Question 10

What role do platelets play in coagulation cascade

Answer 10

• Provide phospholipids that are used by coagulation factors

- Secrete factor V

Question 11

How does thrombin activate platelets

Answer 11

Thrombin activates platelets by activatin the protease activated receptors (PARs) on the surface of platelets
- PARs are G protein coupled receptors

Question 12

What coagulation factors require viatmin K for proper activity

Answer 12

Factors II, VII, IX as well as proteins S, C and Z

Vitamin K was born in 1972 (10, 9, 7, 2)

Question 13

What is the mechanism by which heparin sulphate or heparin regulates thrombin and factor Xa degradation

Answer 13

Heparin binds to antithrombin III (AT) and activates it. AT is an enzyme inhibitor that INACTIVATES thrombin and factor Xa, preventing coagulation initation

Question 14

describe the mechanism by which thrombin/thrombomodulin complex reduces coagulation

Answer 14

complex binds to and activates protein C, a serine protease

- activated protein C (APC) interacts with protein S and the complex INACTIVATES factors Va and VIIIa

Question 15

Why does Factor V Leiden mutation lead to hypercoagulable state

Answer 15

the mutated factor V cannot be deactivated by APC

Question 16

How does Plasminogen regulate fibrinolysis

Answer 16

plasminogen: zymogen that is converted into plasmin (initiation of fibrinolysis)

Question 17

how does Plasmin regulate fibrinolysis

Answer 17

Plasmin: active serine protease that can cleave fibin, thereby dissolving clots

Question 18

How does tPA regulate fibinolysis

Answer 18

Activates plasminogen

Question 19

How does PAI regulate fibinolysis

Answer 19

removal and deactivation of tPA to prevent removal of necessary fibrin clots

Question 20

How does alpha2-plasmin inhibitor regulate fibrinolysis

Answer 20

inhibits plasmin that is NOT already bound to fibrin in effect to negatively regulate the fibrinolytic system

Question 21

Describe the extrinsive pathway

Answer 21

1) damage exposes tissue factor III
2) factor III activates Factor VII
3) activated Factor III, VII and Ca2+ activate Factor X
4) Factor X slowly forms Thrombin from Prothrombin with Ca2+ and Phospholipids
5) Once some Thrombin is made, Thrombin activates Factor V
6) Factor Xa and Factor Va form a prothrombin activator complex that is ALOT FASTER AT turning Prothrombin into Thrombin

Question 22

Describe the Intrinsic Pathway

Answer 22

1) Factor XII is activated by exposure to Collagen
2) Factor XIIa + Ca activates Factor XI
3) Factor XIa + Ca activates Factor IX
4) Factor IXa activates Factor X
5) Factor Xa + Ca + Phospholipids SLOWLY converts Prothrombin into Thrombin
6) Once a LITTLE THROMBIN is made, Thrombin activates Factor VIII
7) Factor VIIIa + Factor IXa + Ca + Phospholipids FORM the TENASE COMPLEX
8) TENASE COMPLEX causes activation of Factor X and RAPID PRODUCTION OF THROMBIN