Vertebrate Physiology - Hemostasis

Front 1

I. What is the initial response to blood vessel damage?

Back 1

vasoconstriction and the sticking together of the opposed endothelial surfaces

Front 2

II. What comes after vasoconstriction and the sticking together of opposed endothelial surfaces?

Back 2

formation of a platelet plug followed by blood coagulation (clotting)

Front 3

III. What happens to form the platelet plug and start blood coagulation?

Back 3

Platelets adhere to exposed collagen in a damaged vessel and release the contents of their secretory vesicles.

Front 4

What do the contents of the secretory vesicles help do?

Back 4

they help cause platelet activation and aggregation

Front 5

What is this process also enhanced by, secreted by, and produced by?

Back 5

This process is also enhanced by von Willebrand factor, secreted by the endothelial cells and by thromboxane A2, produced by the platelets.

Front 6

What does fibrin do?

Back 6

Fibrin forms the bridges between aggregating platelets

Front 7

What do contractile elements in the platelets do?

Back 7

Contractile elements in the platelets compress and strengthen the plug

Front 8

IV. Why doesn't the platelet plug spread along normal endothelium?

Back 8

because the endothelium secretes prostacyclin and nitric oxide, both of which inhibit platelet aggregation

Front 9

V. What is blood transformed into and when? What happens next?

Back 9

Blood is transformed into solid gel when, at the siote of vessel damage, plasma fibrinogen is converted into fibrin molecules, which then bind to each other to form a mesh.

Front 10

VI. What is this reaction catalyzed by, and what does that activate?

Back 10

This reaction is catalyzed by the enzyme thrombin, which also activates factor XIII, a plasma protein that stabilizes the fibrin meshwork

Front 11

VII. What is the end result of the cascade of reactions in which an inactive plasma protein is activated and then enzymatically activates the next protein in the series?

Back 11

The formation of thrombin from the plasma protein prothrombin is the end result of a cascade of reactions in which an inactive plasma protein is activated and then enzymatically activates the next protein in the series.

Front 12

How does Thrombin exert a positive feedback stimulation of the cascade?

Back 12

By activating platelets and several other clotting factors

Front 13

What do activated platelets do that is essential for the cascade?

Back 13

Activated platelets display platelet factor and binding sites for several activated plasma factors

Front 14

VIII. Where does the cascade usually begin in the body and when?

Back 14

THe cascade usually begins via the extrinsic clotting pathway when tissue factor forms a complex with factor VIIa.

Front 15

VIII continued. What happens after tissue factor forms a complex with factor VIIa?

Back 15

This complex activates foctor X, which then catalzyes the conversion of small amounts of prothrombin to thrombin.

Front 16

VIII continued 2. What happens after the conversion of small amounts of prothrombin to thrombin?

Back 16

The thrombin then rectruits the intrinsic pathway by activating factor XI and factor VIII as well as platelets, and this pathway generates large amounts of thrombin.

Front 17

Why does the liver require vitamin K?

Back 17

for the mornal production of prothrombin and other clotting factors.

Front 18

What 3 events limit clotting?

Back 18

1. Tissue factor pathway inhibitor inhibits the tissue factor (factor VIIa complex)
2. Protein C, activated by thrombin, inactivates factors VIIIa and Va
3. ANtithrombin III inactivates thrombin and several other clotting factors

Front 19

What are clots dissolved by?

Back 19

The fibrinolytic system

Front 20

What digests fibrin?

Back 20

A plasms proenzyme (plasminogen) which is activated by plasminogen activators to plasmin

Front 21

What is tissue plasminogen activator secreted by?

Back 21

endothelial cells

(it is activated by fibrin in a clot)

Front 22

What is a hematoma?

Back 22

accumulation of blood in the tissues as a result of bleeding from any vessel type

Front 23

What does von Willebrand factor do?

Back 23

binds to exposed collagen molecules, changes its conformation, and becomes able to bind platelets.

Front 24

What is platelet activation?

Back 24

The process of chemical agents acting locally to induce changes in the metabolism, shape, and surface proteins of the platelets

Front 25

What is the positive feedback phenomenon that causes new platelets to adhere to old ones called?

Back 25

platelet aggregation

Front 26

What is thromboxane A2?

Back 26

-a member of the eicosanoid family
-from arachidonic acid in platelet plasma membrane
-stimulates more platelet aggregation and release of secretory vesicle contents

Front 27

What does fibrinogen do?

Back 27

forms bridges between aggregating platelets

Front 28

What do platelets contain a very high concentration of that helps them to contract?

Back 28

actin and myosin

Front 29

What does the eicosanoid prostacyclin (aka prostaglandin I2) do?

Back 29

inhibits platelet aggregation so the platelet plug does not continuously expand

*synthesized by undamaged endothelial cells

Front 30

What do endothelial cells release in addition to prostacyclin to inhibit platelet adhesion?

Back 30

nitric oxide

Front 31

what does each reaction in the cascade result from?

Back 31

the splitting of a small peptide fragment from the inactive plasma protein precursor, which exposes the active site of the enzyme

Front 32

The liver's production of bile saalts is important for what?

Back 32

Normal intestinal absorption of the lipid-soluble substance VITAMIN K

Front 33

What is Vitamin K necessary for?

Back 33

production of prothrombin and several other clotting factors