41 Questions
Which components are involved in both hemostasis and thrombosis?
Endothelial cells, platelets, factors of the coagulation cascade
What is the main difference between hemostasis and thrombosis?
Location of blood clot formation
What does hemostasis maintain besides homeostasis?
Blood fluidity
What happens when the delicate balance between pro and anti-thrombotic activities of blood is destroyed?
Excessive bleeding or thrombosis
Which factor is activated by thrombin and is involved in the cross-linking of fibrin?
Factor XIII
What is the major function of plasmin?
Fibrinolysis and inhibition of fibrin polymerization
Which molecule is a potent inhibitor of platelet adhesion and aggregation, as well as a vasodilator?
Prostacyclin (PGI2)
Which molecule binds thrombin, inhibiting its activity, and then forms a complex to inhibit protein C?
Thrombomodulin
Which plasminogen activator is synthesized principally by endothelium and is most active when bound to fibrin?
Tissue-PA
What is the additional function of thrombin apart from its involvement in the coagulation cascade?
Activation of Proteases Activated Receptors (PARs)
What are the major functions of plasmin?
Fibrinolysis and inhibition of fibrin polymerization
Which molecule inhibits platelet adhesion and aggregation as well as acts as a vasodilator?
Prostacyclin (PGI2)
Which molecule binds thrombin, inhibiting its activity, and then forms a complex to inhibit protein C?
Thrombomodulin
Which plasminogen activator is synthesized principally by endothelium and is most active when bound to fibrin?
Tissue-PA
What is the central event in the coagulation cascade?
Conversion of factor X into Xa
Which molecule is responsible for platelet adhesion to the vessel wall?
Adhesion molecules
What is the role of phosphatidyl serine in platelet activation?
Binding prothrombin and activating the coagulation cascade
Which factor is crucial for the conversion of fibrinogen into fibrin and the cross-linking of fibrin fibers?
Thrombin
What do activated platelets release to aid in hemostasis?
$ ext{PDGF}$
What is the primary function of fibrinogen in hemostasis?
Platelet aggregation and clot formation
How do platelets adhere to the vessel wall?
Through adhesion molecules
Which molecule plays a significant role in factor X activation?
Calcium ions
What flips out to the outer membrane of activated platelets and plays a role in activating the coagulation cascade?
Phosphatidyl serine
Which enzyme is crucial for converting fibrinogen into fibrin and cross-linking fibrin fibers?
Thrombin
What plays a crucial role in orchestrating hemostasis through factors production and binding of platelets to broken endothelium?
Endothelial cells
Which molecule activates Antithrombin III?
Heparin-like molecules on endothelial cells
What is the main function of Antithrombin III?
Inhibition of the activity of thrombin and other coagulation factors
Which activity of endothelial cells contributes to a fibrinolytic effect?
Production of tissue plasminogen activator
What effect does heparin have on thrombin function?
Blocks thrombin function by forming a complex with Antithrombin III
Why would administering heparin be ineffective if a thrombus is already formed in a patient?
It would be useless to stop the activity as the thrombus is already formed
Which is the primary function of platelets?
Performing hemostasis by forming a primary hemostatic plug
Which molecules are released from platelet granules during hemostasis?
Fibrinogen, fibronectin, and coagulation factors
Which molecule mediates the adhesion and aggregation of platelets by binding to $GpIIb-IIIa$?
$vWF$
What is the role of integrins in platelet adhesion and aggregation?
Crucial role in platelet adhesion and aggregation
What happens when there is a deficiency in $vWF$ or integrins?
Result in thrombosis or bleeding
$GpIIb-IIIa$ binds to which molecule during platelet adhesion?
Fibrinogen
Which cells produce vWF and release it when the endothelium is damaged?
Endothelial cells
What is the initial step in the body's response to a ruptured vessel wall?
Vasoconstriction
What is the main function of platelets during hemostasis?
Forming a primary hemostatic plug
Which receptor is present on the membrane of platelets for adhesion and aggregation?
Integrins
Which molecule mediates the adhesion and aggregation of platelets by binding to $GpIb$?
vWF
Study Notes
- When a vessel wall is ruptured, the body initiates a hemostatic process to stop the bleeding.
- The first step is vasoconstriction, which is a reflex response causing the vessels to constrict and reduce blood loss.
- Next is primary hemostasis, where platelets adhere to the sub-endothelium and form a primary hemostatic plug.
- Platelets are anucleated cells with a short life-span, their main function is to perform hemostasis.
- Platelets contain granules (alpha and delta) that release important molecules for hemostasis, such as fibrinogen, fibronectin, and coagulation factors.
- Platelets have receptors on their membrane, such as selectins, GPCRs, and integrins, for adhesion and aggregation.
- Integrins, such as glycoprotein IIb/IIIa and glycoprotein Ib (GpIb), play a crucial role in platelet adhesion and aggregation.
- vWF, a multimeric glycoprotein, mediates the adhesion and aggregation of platelets by binding to GpIIb-IIIa.
- Endothelial cells produce vWF and release it when the endothelium is damaged.
- During platelet adhesion, vWF binds to GpIb on platelets, then GpIIb-IIIa binds to fibrinogen, causing platelet aggregation.
- A deficiency in vWF or integrins can result in thrombosis or bleeding, as platelets are not correctly bound to the sub-endothelium or to each other.
Test your knowledge on platelet activation and von Willebrand factor (vWF) in blood. This quiz covers the functions of vWF in endothelial cells and plasma, as well as the process of platelet activation mediated by G protein-coupled receptors (GPCRs).
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