Hemostasis

Question 1

what is another name for platelets, and what are they derived from?

Answer 1

thrombocytes, they are derived from megakaryocytes

Question 2

what is the regulation of the production of platelets controlled by?

Answer 2

TPO

Question 3

what is TPO produced by?

Answer 3

kidney and liver

Question 4

what is the role of TPO?

Answer 4

it increases the differentiation and maturation rate of hematopoietic stem cells resulting in more megakaryocytes and platelets

Question 5

what does thrombopoietin (TPO) bind to?

Answer 5

c-MPL receptor

Question 6

where is the c-MPL receptor found?

Answer 6

on megakaryocytes and other hematopoietic cells

Question 7

how is TPO secretion controlled?

Answer 7

by itself and platelets themselves

Question 8

what effect will a high number of platelets have on TPO?

Answer 8

the TPO will more likely bind to the c-MPL, so there will be less free TPO

Question 9

what effect will a low number of platelets have on TPO?

Answer 9

the TPO will not bind to c-MPL as readily, so there will be more free TPO

Question 10

What are the four basic steps of hemostasis?

Answer 10

vascular spasm, formation of platelet plug, formation of blood clot, repair of damage

Question 11

what is the purpose of vascular spasm/ vasospasm?

Answer 11

it disrupts blood flow to keep blood above the spasm and avoid further blood loss

Question 12

what are the platelet factors that contribute to vasospasm?

Answer 12

serotonin and thromboxane A2

Question 13

what is adhesion of platelets to each other and endothelial cells initiated by?

Answer 13

the activation of platelet receptors GP Ib/Ia

Question 14

what does the GP Ib/Ia bind to on the endothelial cells?

Answer 14

VWF

Question 15

what is the first step of formation of the platelet plug?

Answer 15

adhesion

Question 16

what is the second step of formation of the platelet plug?

Answer 16

activation

Question 17

what happens once the platelet receptors are activated?

Answer 17

they release ATP, ADP, serotonin, and Ca2+ from their dense granules; they release growth factors, VWF, factor V, and fibrinogen from their alpha-granules; they generate thromboxane A2

Question 18

what happens once ADP, serotonin, and thromboxane is released from the dense granules?

Answer 18

they activate additional platelets which promotes aggregation

Question 19

what does the ADP bind to?

Answer 19

P2Y12 receptors on platelets

Question 20

what does binding of the ADP on the P2Y12 receptors cause?

Answer 20

a conformation change in the GP IIb/IIIa

Question 21

what does a conformation change in the GP IIb/IIIa cause?

Answer 21

the binding of fibrinogen

Question 22

what happens when fibrinogen can bind?

Answer 22

it bridges other platelets and participates in forming the platelet plug

Question 23

what is aspirin?

Answer 23

a cyclooxygenase inhibitor

Question 24

what is the action of aspirin?

Answer 24

it inhibits clotting by reducing release of thromboxane A2

Question 25

what is Clopidogrel (Plavix)?

Answer 25

an antiplatelet agent

Question 26

what is the action of clopidogrel (plavix)?

Answer 26

it inhibits P2Y12 receptors- so it blocks further platelet activation and aggregation

Question 27

what is the first thing to occur during blood clot formation?

Answer 27

there will be activation of pro thrombin activator, which will then activate thrombin

Question 28

thrombin will then work on fibrinogen to make what?

Answer 28

fibrin monomers

Question 29

what do the fibrin monomers eventually become?

Answer 29

stable fibrin

Question 30

what is the main purpose of the blood clot formation step in hemostasis?

Answer 30

it starts to contract everything

Question 31

if a patient doesn’t have VWF, what will be the issue?

Answer 31

an issue with adhesion

Question 32

if a patient doesn’t have GPIIb-GPIIIa, what will be the issue?

Answer 32

they will struggle with the aggregation process