Question

1. In hemostasis

A.Erythropoietin stimulates erythrocyte production

B.Platelets stimulate the intrinsic pathway

C.von Willenbrand factor is an anticoagulant

D. Thrombin converts fibrinogen to fibrin

2.

Which of the following term and definition pair is correctly matched?

Group of answer choices

ESV : the volume of blood in the ventricle after the final filling

pacemaker potential : spontaneous depolarization

P wave : ventricle depolarization

systole : relaxation

3.

Which type of capillary would allow proteins to pass through the gaps between the endothelial cells?

Discontinuous

No capillaries allow proteins to pass through.

Fenestrated

Continuous

4.

When the ventricles are no longer acting as a syncytium and can't pump blood, they are in __________.

bradycardia

ventricular tachycardia

AV node block

fibrillation

Answer 1

1. Options D is correct

Justification: Thrombin is an enzyme generated by blood-clotting proteins and it converts fibrinogen to fibrin and the reaction of this conversion leads to the formation of fibrin clot.

Justification for incorrect options:

• Option 'A' is incorrect because, erythropoietin is a hormone which is released when oxygen levels are low in the kidney and this erythropoietin stimulates the bone marrow to produce erythrocytes but it will NOT stimulate the production of erythrocytes.
• Option 'B' is incorrect because activated platelets activate intrinsic pathway but they will NOT stimulate the intrinsic pathway.
• Option 'C' is incorrect because Von Willebrand factor (VWF) plays major role in blood coagulation but NOT in anti-coagulation. So, VWF is NOT an anti-coagulant.

2. Option 'B' (pacemaker potential: spontaneous depolarization) is the correct matching

Justification: Cells within the sinoatrial node (SA node) are the pacemaker cells and that specific site is known as pacemaker site. Spontaneous depolarization takes place in the phase 4 of the pacemaker site and that spontaneous depolarization is known as 'pacemaker potential', which in turn triggers the action potential.

Justification for incorrect options:

• Option 'A' is incorrect matching because end-systolic volume (ESV) is the volume of blood in ventricle at the end of contraction or at the beginning of filling but NOT after the final filling. The volume of blood in ventricle after final filling is the end-diastolic volume (EDV) but NOT end-systolic volume (ESV).
• Option 'C' is incorrect matching because P wave denotes the atrial depolarization but NOT the ventricular depolarization. (QRS complex denotes ventricular depolarization)
• Option 'D' is incorrect matching because systole is the phase of contraction of heart but NOT the relaxation of heart. (Relaxation is the diastolic phase)

3. Option 'A' (discontinuous) is correct

Justification: Discontinuous capillaries or sinusoidal capillaries have wider diameters about 30-40 micrometers and they allows various serum proteins to pass through the gaps between them. So, this option is correct.

Justification for incorrect options:

• Option 'B' is incorrect because capillaries allows passage of proteins to pass through their gaps.
• Option 'C' is incorrect because fenestrated capillaries allows only small molecules to pass through them but they won't allow proteins.
• Option 'D' is incorrect because continuous capillaries have small diameter and allows water, gases and small molecules to pass through them but they won't allow proteins.

4. Option 'C' (AV node block) is correct

Justification: When the ventricle stops pumping blood, it is due to AV node block.

• Other options are incorrect because they are not about the stoppage of pumping of blood.

Thank you!