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

Incomplete double circulation occurs in

1. Fishes

2. Amphibians

3. Reptiles

4. Both 2 & 3

_________ is known as the graveyard of RBCs.

1.  Liver

2.  Spleen

3.  Pancreas

4.  Bone marrow 

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 

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 

Atrial systole

1.  Increases the flow of blood into the ventricles by 70 percent

2.  Is due to the generation of the action potential in AVN

3.  Increases the flow of blood into the ventricles by 30 percent

4.  Coincides with ventricular systole

Which of the following statements is not true for the human heart?

1. Adrenal medullary hormones can increase the cardiac output

2. Neural signal through the sympathetic nerves can initiate the heart beat

3. Increase in BMR due to thyroxine can indirectly increase heart rate

4. Strength of ventricular contraction and cardiac output is increased by catecholamines