Which of the following is known as the natural pacemaker of the heart?

1.  Sino atrial node

2.  Atrioventricular node

3.  Bundle of His

4.  Purkinje fibers 

A patch of nodal tissue responsible for initiating the rhythmic contractile activity of heart is present in

1.  Lower left corner of the left ventricle

2.  Upper right corner of the right atrium

3.  Lower left corner of the right ventricle

4.  Upper left corner of the left atrium 

The cardiac pacemaker in a patient fails to function normally. The doctors find that an artificial pacemaker is to be grafted in him. It is likely that it will be grafted at the site of

1.  Atrioventricular bundle

2.  Purkinje system

3.  Sinoatrial node

4.  Atrioventricular node 

The impulse of heartbeat originates from

1.  SA node

2.  AV node

3.  Vagus nerve

4.  Cardiac nerve 

Rate of heartbeat is determined by 

1.  Purkinje fibers

2.  Papillary muscles

3.  AV-nodes

4.  SA-node 

_________ is known as the graveyard of RBCs.

1.  Liver

2.  Spleen

3.  Pancreas

4.  Bone marrow 

The life span of the erythrocytes in humans is about

1.  120 days

2.  150 days

3.  190 days

4.  180 days

Oxygen carrier in human blood is 

1.  Carbonic anhydrase

2.  Haemoglobin

3.  Haemocyanin

4.  Both (1) & (3) 

Erythroblastosis foetalis occurs when a factor from mother passes into the foetus through the placenta. The factor is 

1. Rh antigen

2. Rh antibodies

3. Agglutinins

4. ABO antibodies

Open circulatory system is present in

1. Arthropods

2. Molluscs

3. Annelids

4. Both 1 & 2