HEMOSTASIS II

Question 1

Mention the platelet agonists

Answer 1

1. Collagen
2. Adenosine diphosphate (ADP)
3. Thrombin
4. Epinephrine
5. Arachidonic acid

Question 2

Mention the stages/processes involved i primary hemostasis

Answer 2

1. Platelet adhesion
2. Platelet activation
3. Shape change
4. Platelet secretion
5. Platelet aggregation

Question 3

Explai the process of platelet adhesion

Answer 3

1. Major interaction is the binding of platelet receptor glycoprotein Ib (GPIb)/IX to vWF, which binds to collagen
2. vWF: Stored in alpha granules in platelets and weibelpalade bodies in endothelial cells
3. Important step that triggers several events leading to platelet activation

Question 4

what trigers platelet activation

Answer 4

It is triggered after platelet adhesion or exposure to agonist

Question 5

what happens to the platelet during platelet activation

Answer 5

1. shape chage
2. Altered orientation of phospholipids
3. New receptor expression
4. Changes in biochemistry

Question 6

What triggers shape change

Answer 6

It occurs after agonist stimulation (appearace of pseudopods, will convert back to original shape if stimulus is not sufficient)

Question 7

what occurs after agonist stimulation in the cotext of shape change

Answer 7

after agoist stimulation, platelets undergo shape change, which involves the appearance of pseudopods. if the stimulus is not sufficient the pseudo pods can revert back to their original shape

Question 8

explain the role of microtubules, microfilaments and intermediate filaments during shape chage

Answer 8

During shape change, these cytoskeletal components reorganize within activated platelets.

Question 9

what happens during platelet secretion

Answer 9

Requires ATP. open canalicular system fuses with granular membrane and contents of alpha granules and dense bodies are released to outside of the platelet.

Question 10

explain platelet aggregation

Answer 10

vWF binding to GPIb/IX activates an intracellularsignaling pathway that results inthe activation of GPIIb/IIIa , which then binds to fibrinogen

Fibrinogen forms bridges to other GPIIb/IIIa receptor on other activated platelets, resulting in platelet aggregates (Ca 2+ is needed for aggregation)

Fibrinogen and ca2+ are delivered locally from granules ad dense tubular systems