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Cardiovascular Physiology > Haemostasis: Role of Platelets > Flashcards

Haemostasis: Role of Platelets Flashcards

1
Q

What are Platelets mechanism of action?

A

Rapidly adhere to site of injury and to each other leading to formation of platelet plug

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2
Q

What leads to the formation of fibrin?

A

Activation of parallel clotting factors

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3
Q

What two components seal off the wound?

A

Aggregated platelets and fibrin

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4
Q

What are platelets derived from?

A

Megakaryocytes in bone marrow

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5
Q

What do platelets not contain?

A

Nucleus

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6
Q

What increases platelets surface area?

A

Open canalicular system (OCS)

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7
Q

What do platelets’ dense granules contain?

A

Serotonin, ADP and Ca2+

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8
Q

What do platelets alpha granules contain?

A

Proteins

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9
Q

What does the Golgi of the platelets provide evidence for?

A

Ongoing protein synthesis

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10
Q

What do platelets bind to?

A

Collagen and other matrix molecules

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11
Q

When is collagen exposed?

A

When vessel wall is injured

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12
Q

What are 2 collagen receptors?

A

GPIb/V/IX
GPVI

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13
Q

What does GPIb/V/IX need to attach to collagen?

A

von Willebrand factor (VWF)

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14
Q

What does the GPIb/V/IX-VWF-collagen interaction allow for?

A

Binding of platelets to vessel wall in high shear conditions eg. arteries

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15
Q

What does GPVI allow for?

A

Direct binding of platelets

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16
Q

What triggers release of alpha and dense granules?

A

Collagen receptor signalling

17
Q

What is the role of ADP?

A

Potent platelet activator
Produces surfaces for effective clotting - stimulates further platelet activation

18
Q

What synthesis does platelet activation lead to?

A

Thromboxane A2 (TXA2) synthesis

19
Q

What does platelet binding to TXA2 receptors cause?

A

Further activation

20
Q

What does vessel wall injury induce?

A

Clotting cascade -> production of thrombin

21
Q

What thrombin receptors do platelets have?

A

Protease activated receptors (PARs)

22
Q

What does PAR activation contribute to?

A

Amplification of platelet activation

23
Q

What do activated platelets contain?

A

Intergrin (alpha II and beta 3)

24
Q

What does intergrin cause?

A

Inside out signalling leads to fibrinogen binding

25
Q

What does fibrinogen binding result in?

A

Crosslinking of platelets and formation of platelet plug

26
Q

What inhibits platelet activation?

A

Endothelial cells

27
Q

What 3 ways do ECs inhibit platelet activation?

A
  1. ADP-degrading enzyme at cell surface (Ecto ADPase)
  2. Prostacyclin release - binds to G protein coupled receptor on platelet which inhibits cAMP signalling
  3. NO release induces synthesis of cGMP

Cardiovascular Physiology (21 decks)

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