Exam 4 - Weber Hockerman Campbell Thurman

Question 1

platelets derive from __________

Answer 1

megakaryotes

Question 2

platelets have no _________

Answer 2

nucleus or genes

Question 3

what are the three steps of platelet formation?

Answer 3

adhesion, secretion, aggregation

Question 4

platelets: adhesion is mediated by:

Answer 4

• GP Ia binding to collagen
• GP Ib binding to vWF bridged to collagen
• shape changes facilitates receptor binding
• intact endothelial cells secrete PGI2 (prostacyclin) to inhibit thrombogenesis)

Question 5

platelets: secretion release reaction

Answer 5

• degranulation
• platelet granules release ADP, 5-HT, TXA2
• these molecules activate and recruit other platelets
• TXA2 and 5HT are potent vasoconstrictors

Question 6

what molecules are released from platelet granules

Answer 6

ADP, TXA2, 5-HT

Question 7

which molecules released from platelets are potent vasoconstrictors

Answer 7

TXA and 5-HT

Question 8

platelet aggregation steps

Answer 8

• ADP, 5-HT, TXA2 activation induces conformation of GPIIb/IIIa receptors to bind fibrinogen
• platelets are crossed-linked by fibrogen
• forms temporary hemostatic plug
• platelets contract to form irreversible fused mass
• fibrin stabilizes and anchors aggregated platelets
• forms surface for clot formation

Question 9

what does GPIIb/IIIa bind to?

Answer 9

fibrinogen

Question 10

platelets are _______ by fibrinogen

Answer 10

cross-linked

Question 11

COX-1 inhibitors MOA

Answer 11

irreversible inhibition of TXA2 synthesis in platelets

Question 12

aspirin use leads to a _______ loss of platelet COX1 activity

Answer 12

permanent

Question 13

indications of aspirin

Answer 13

prophylaxis and treatment of arterial thromboembolic disorders

• prevents coronary thrombosis in unstable angina
• adjunct to thrombolytic therapy
• reducing recurrence of thrombotic stroke

Question 14

clinical actions of aspirin

Answer 14

• prolongs bleeding time but no increase in PT time
• hemostasis returns to normal 36 hours after last dose

Question 15

side effects of aspirin

Answer 15

• upper GI bleeding
• aspirin overdose

Question 16

why do selective COX inhibitors cause increased CV risk

Answer 16

selective COX2 inhibitors block synthesis of prostacyclin while not preventing the synthesis of TXA2 (increased risk of clotting)

Question 17

ADP RIs: P2Y1s couple to which pathway

Answer 17

Gq - PLC - IP3 - Ca2+ - pathway

Question 18

ADP RIs: P2Y12s couple to which pathway

Answer 18

G1 and inhibition of adenylyl cyclase

Question 19

activation of both P2Y1 and P2Y12 receptors is not required for platelet activation by ADP

Answer 19

false

Question 20

Name the P2Y12 ADP Receptor inhibitor

Answer 20

clopidogrel (plavix)

Question 21

MOA of clopidogrel (plavix)

Answer 21

irreversibly block ADP receptor on plateelt and subsequent activation of GP IIb/IIIa

Question 22

duration of action of clopidogrel after d/c

Answer 22

several days after last dose