3.2: Platelet Activation And Microplatelets

Question 1

Sequence of events of adhesion:

Answer 1

1. Collagen
2. Vwf
3. GP lb/IX/V
4. ADAMTS-13
5. GP VI
6. TXA2 and ADP
7. TPa and TPb
8. P2Y1 and P2Y12
9. A2B1

Question 2

Sequence of events of aggregation:

Answer 2

1. Tissue factor
2. Thrombin
3. PAR1 and PAR4
4. COAT platelets
5. TXA2 and ADP
6. GP IIb/IIIa receptor
7. P-selectin
8. Phosphatidylserine

Question 3

The combination that triggers secondary hemostasis

Answer 3

1. Polar phospholipid exposure on activated platelets
2. Platelet fragmentation with cellular microparticle release
3. Secretion of the platelet’s alpha grange and dense granule contents

Question 4

Sequence of events of secretion

Answer 4

1. STRs
2. GP VI
3. Intermediate filaments
4. Actin microfilament
5. Alpha granules
6. Lysosomes
7. Dense granules
8. Phosphatidylserine

Question 5

Is disrupted and exposed during blood vessel injury

Answer 5

Collagen

Question 6

Is released when endothelial cells become
damaged, then adheres to the site of injury;
Under shear stress, it becomes thread-like
as it unrolls and exposes sites that weakly
bind the GPIbα portion of the GP Ib/IX/V
receptor

Answer 6

vWF

Question 7

Platelet membrane receptor in adhesion

Answer 7

GP Ib/IX/V

Question 8

A liver-secreted plasma enzyme which
digests larger vWF multimers into smaller, less biologically active forms; Localizes the
platelet-vWF interaction

Answer 8

ADAMTS-13

Question 9

Collagen binding to ______ triggers internal platelet activation pathways, releasing TXA2 and ADP, an outside-in reaction

Answer 9

GP VI

Question 10

Are agonists that bind to the receptors TPα
and TPβ and P2Y1 and P2Y12 ,
respectively, for ADP that triggers an
inside-out reaction that raises the affinity of
integrin α2β1 for collagen

Answer 10

TXA2 and
ADP

Question 11

STRs of adhesion

Answer 11

TPα and TPβ
P2Y1 and P2Y12

Question 12

Increased affinity for collagen

Answer 12

α2β1

Question 13

Blood vessel injury exposes these and are expressed on subendothelial smooth muscle cells and fibroblasts; Triggers the production of thrombin

Answer 13

Tissue factor

Question 14

Cleaves platelet PAR1 and PAR4

Answer 14

Thrombin

Question 15

STRs of aggregation

Answer 15

PAR1 and PAR4

Question 16

“collagen and thrombin activated” platelets; Generated by the activation of thrombin formation

Answer 16

COAT platelet

Question 17

Are platelet activators that is secreted from the platelet granules to the microenvironment, where they activate neighboring platelets through their respective receptors and trigger inside-out activation of integrin αIIbβ3 (GP IIb/IIIa receptor)

Answer 17

TXA2 and ADP

Question 18

Binds to the RGD sequences of fibrinogen and vWF; Supports platelet-to-platelet binding

Answer 18

GP IIb/IIIa receptor

Question 19

Moves from the alpha granule membrane to the surface membrane to promote binding of platelets with leukocytes

Answer 19

P-selectin

Question 20

The more polar phospholipid molecules flip to the outer layer; Platelets change in shape from discoid to round and extend pseudopods

Answer 20

Phosphatidylserine

Question 21

Triggers actin microfilament contraction

Answer 21

STRs
GP VI

Question 22

Also contract, moving the circumferential microtubules inward compressing the granules

Answer 22

Intermediate filaments

Question 23

Contracts due to the outside-in activation

Answer 23

Actin microfilament

Question 24

Flows through SCCS with the lysosomes; Are large molecule
coagulation proteins that participate in secondary hemostasis; Its contents (fibrinogen, factors V and VIII, and vWF) are secreted and increase the localized concentrations of the essential coagulation proteins, further supporting the action of tense and prothrombinase

Answer 24

Alpha granules

Question 25

Flows through the SCCS with alpha granules

Answer 25

Lysosomes

Question 26

Are small vasoconstrictors and platelets agonists that amplify primary hemostasis

Answer 26

Dense granules

Question 27

Is a polar phospholipid on which the factor IX/VIII (tenase) and X/V (prothrombinase) complexes assemble; Is supported by the ionic calcium secreted by the dense granules; OIs presented on the platelet membrane surface providing a localized cellular milieu that supports coagulation

Answer 27

Phosphatidylserine

Question 28

Are formed after exposure of platelets to strong agonists or shear stress

Answer 28

Platelet Microparticles

Question 29

Are membrane-derived vesicles that form in response to an activating stimulus that increases the platelet intracellular concentration of calcium

Answer 29

Platelet Microparticles

Question 30

Control cellular activation for all cells at the inner membrane surface

Answer 30

G-proteins

Question 31

αβγ heterotrimers that bind guanosine diphosphate (GDP) when inactive

Answer 31

G-PROTEINS

Question 32

of the heterotrimer briefly dissociates, exerts enzymatic guanosine triphosphate activity and hydrolyzes the bound GTP to GDP, releasing a phosphate radical

Answer 32

Gα portion

Question 33

EICOSANOID SYNTHESIS Alternatively called the

Answer 33

prostaglandin, cyclooxygenase, or thromboxane pathway

Question 34

One of the two essential platelet activation pathways triggered by G-proteins in platelets

Answer 34

EICOSANOID SYNTHESIS

Question 35

An inner phospholipid whose number 2 carbon binds numerous types of unsaturated fatty acids, but especially 5, 8, 11, 14-eicosanoid acid (arachidonic acid)

Answer 35

Phosphatidylinositol

Question 36

a membrane enzyme that cleaves the ester bond connecting the number 2 carbon of the triglyceride backbone with arachidonic acid

Answer 36

Phospholipase A2

Question 37

is released to the cytoplasm as it is cleaved

Answer 37

Arachidonic acid

Question 38

Converts arachidonic acid to prostaglandin G2 and prostaglandin H2

Answer 38

Cyclooxygenase

Question 39

Acts on prostaglandin H2 to produce TXA2

Answer 39

Thromboxane A2

Question 40

Binds membrane receptors TPα and TPβ (inhibits adenylate cyclase activity and reducing cAMP concentrations, which mobilizes ionic calcium from the DTS)

Answer 40

TXA2

Question 41

Is incorporated in place of the thromboxane synthetase

Answer 41

Prostacyclin synthetase

Question 42

The eicosanoid pathway end point for the endothelial cells

Answer 42

Prostaglandin I2 or prostacyclin

Question 43

Binds to the IP receptor activating the IP3-DAG pathway

Answer 43

Prostaglandin I2 or prostacyclin

Question 44

Leads to the acceleration of adenylate cyclase, an increase in cAMP, and a sequestration of ionic calcium to the DTS

Answer 44

Prostaglandin I2 or prostacyclin

Question 45

Is the second G-protein-dependent platelet activation pathway

Answer 45

IP3-DAG ACTIVATION PATHWAY

Question 46

Phospholipase C cleaves PIP2 to form

Answer 46

IP3 and DAG

Question 47

are second messengers for intracellular activation

Answer 47

IP3 and DAG

Question 48

Promotes release of ionic calcium from the DTS (triggers actin microfilament contraction)

Answer 48

IP3

Question 49

Also activates phospholipase A2

Answer 49

IP3

Question 50

Activates phosphokinase C (triggers phosphorylation of the protein pleckstrin)

Answer 50

DAG