antiplatelet drugs Flashcards

1
Q

what are the steps to the formation of platelets?

A

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

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2
Q

what are the general properties of platelets?

A

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

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3
Q

what does thrombopoietin?

A

it regulates platelet production

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4
Q

what are the physiological properties of platelets?

A

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

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5
Q

what is the first response to vascular inhury?

A

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

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6
Q

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

A
  • 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
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7
Q

what happens in platelet plug formation?

A
  • 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
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8
Q

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

A

integrin receptors are important in regards to collagen presence

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9
Q

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

A

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

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10
Q

what occurs in adhesion of platelets?

A

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

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11
Q

what do the granules released by activated platelets contain?

A

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

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12
Q

what happens in secondary homeostasis

A
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13
Q

what happens in primary homeostasis

A
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14
Q

what does factor X do?

A
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15
Q

what happens in the intrinsic pathway?

A

it occurs within the damaged…

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16
Q

what is the mechanism of action for heparin

A

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

17
Q

what is the antidote to heparin?

A

heparin antagonist = Protamine sulfate

18
Q

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

A

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

19
Q

what is the good thing about warfarin?

A

it can be easily reversed by vitamin K

20
Q

what is warfarin?

A

its a vitamin K antagonist

21
Q
A