antiplatelet drugs

Question 1

what are the steps to the formation of platelets?

Answer 1

haemocytoblast-> myeloid stem cell-> megakaryoblast-> promegakaryocyte-> megakaryocyte-> platelets

Question 2

what are the general properties of platelets?

Answer 2

theyre very small, theres lots of them, 250,000-500,000 per cubic vasculature
they survive from 7-10 days
theyre formed in the bone marrow

Question 3

what does thrombopoietin?

Answer 3

it regulates platelet production

Question 4

what are the physiological properties of platelets?

Answer 4

o Adhesion – ability to stick to the foreign and damaged surface
o Aggregation – ability to form a clump (cork)
o Agglutination – pasting of thrombocytes one with another

Question 5

what is the first response to vascular inhury?

Answer 5

vasoconstriction
compression of the vessel by the blood escaping
injury ‘chemicals’ are released by injured cells
reflexes from adjacent pain receprors

Question 6

what are the steps involved in the formation of a platelet plug?

Answer 6

• platelets attach to damaged vessel wall to plug it
• platelets produce thromboxane A2
• serotonin and histamine release enhances vascular contraction
• ADP - attracts and stimulates platelets at site
  prostacyclin - inhibits aggregation at other sites
• a sharply cut vessel undergoes less spasm i.e. it bleeds for longer and a toren vessel

Question 7

what happens in platelet plug formation?

Answer 7

• the platelets aggregate to control the blood loss from the vessel
• if damage is small, then the formation of the plug stops the bleeding
• platelets undergo dynamic change in appearance and begin the process of adhesion and activation due to exposure to collagena nd other foregin substances

Question 8

what receptors are improtant in the formation of platelet plug formation with collagen?

Answer 8

integrin receptors are important in regards to collagen presence

Question 9

what foregin substances cause the platelet to undergo dynmic change in appearance?

Answer 9

antigen-antibody complexes, thrombin, proteolytic enzymes, endotoxins, and viruses

Question 10

what occurs in adhesion of platelets?

Answer 10

the platelets swell and become sticky and adhere to collagen fibril on the basement membrane, it requires von williebrand factor (vWF) adhere to collagen fibrils on the basement membrane

Question 11

what do the granules released by activated platelets contain?

Answer 11

containing vWF, factor V, PDGF, heparin-neutralizing protein, and ADP (attracts other platelets)

Question 12

what happens in secondary homeostasis

Question 13

what happens in primary homeostasis

Question 14

what does factor X do?

Question 15

what happens in the intrinsic pathway?

Answer 15

it occurs within the damaged…

Question 16

what is the mechanism of action for heparin

Answer 16

o major anticoagulant effect by inactivating thrombin and activated factor X (factor Xa) through an antithrombin (AT)-dependent mechanism. The activated AT then inactivates thrombin and factor Xa

Question 17

what is the antidote to heparin?

Answer 17

heparin antagonist = Protamine sulfate

Question 18

what is the mechanism of action to the haparin anatgonist to reverse the effects of it?

Answer 18

Protamine is a strongly basic substance that combines with the strongly acidic heparin to form a stable (salt) complex. The protamine-heparin complex has no anticoagulant activity

Question 19

what is the good thing about warfarin?

Answer 19

it can be easily reversed by vitamin K

Question 20

what is warfarin?

Answer 20

its a vitamin K antagonist