A specialised nodal tissue embedded in the lower corner of the right atrium, close to Atrio-ventricular septum, delays the spreading of impulses to heart apex for about 0.1 sec.

This delay allows -

1. blood to enter aorta.

2. the ventricles to empty completely.

3. blood to enter pulmonary arteries.

4. the atria to empty completely.

All the components of the nodal tissue are autoexcitable. Why does the SA node act as the normal pacemaker?

Which type of white blood cells are concerned with the release of histamine and the natural anticoagulant heparin?

Hemolytic disease of the newborn (HDN) may occur in the feotus of a second pregnancy if:

1. The mother is ${\mathrm{Rh}}^{+}$ and the baby is ${\mathrm{Rh}}^{-}$

2. The mother is ${\mathrm{Rh}}^{+}$ and the baby is ${\mathrm{Rh}}^{+}$

3. The mother is ${\mathrm{Rh}}^{-}$ and the baby is ${\mathrm{Rh}}^{-}$

4. The mother is ${\mathrm{Rh}}^{-}$ and the baby is ${\mathrm{Rh}}^{+}$

Which of the following statements is not correct about
ECG?

1. P wave represents atrial depolarisation.

2. QRS wave initiates ventricular contraction.

3. The end of T wave marks the end of ventricular
systole.

4. Q wave marks the beginning of atrial systole.

Erythroblastosis fetalis condition arises when a:

1. Rh (+) female carries a Rh(–) foetus for the
first time.

2. Rh (+) female carries a Rh(–) foetus for the
second time.

3. Rh (–) female carries a Rh (+) foetus for the
first time.

4. Rh (–) female carries a Rh (+) foetus for the
second time.

Which of the following have no nuclei and originate as pinched-off cytoplasmic fragments of large cells in the bone marrow?
1. Mature RBC
2. Reticulocytes
3. Thrombocytes
4. Macrophages

Erythroblastosis fetalis can be prevented during a second pregnancy in a Rh negative mother who is likely to carry a Rh positive fetus by:

1. Administering anti – Rh antibodies to the mother just before the delivery of the second child

2. Administering Rh antigen to the mother just after the delivery of the first child

3. Administering Rh antigen to the mother just before the delivery of the second child

4. Administering anti – Rh antibodies to the mother just after the delivery of the first child

During a cardiac cycle:
1. About 70 ml of blood is pumped by the two ventricles
2. The left atrium and the left ventricle contract simultaneously
3. More blood is pumped into the systemic than in pulmonary circulation
4. The atria contract prior to the ventricles

Amongst the following, a molecule that would lead to coagulation of the blood would be:
1. prostacyclin
2. tissue factor or thromboplastin
3. plasmin
4. tissue plasminogen activator