Oxalates and citrates are used as anticoagulants in stored blood because they:

1. Chelate calcium ions

2. Act as competitive inhibitors of vitamin K

3. Potentiate anti-thrombin III

4. Activate heparin

With respect to blood, the composition of lymph can be expressed as:

1. No RBc, No Plateletes, Less proteins, Less calcium and phosphorus, Predominant corpuscles lymphocytes.

2. No RBc, No Plateletes, Less proteins, More calcium and phosphorus, Predominant corpuscles lymphocytes.

3. No RBc, Less or no Plateletes, Less proteins, Less calcium and phosphorus, Predominant corpuscles macrophages.

4. No RBc, less Plateletes, Less proteins, Less calcium and phosphorus, Predominant corpuscles monocytes.

Histamine in the blood is secreted by:

A person with AB blood group:

1. Has A and B antigens in his plasma

2. Lacks any antibodies on RBC surface

3. Can receive blood transfusion from a person of his own group.

4. Can donate blood to all other group recipients

The inter-atrial septum in the human heart can be best described as:

1. A thin muscular wall

2. A thick muscular wall

3. A thin fibrous tissue

4. A thick fibrous tissue

The sino-atrial node is the normal pacemaker of the human heart because:

1. It is located in the right atrium.

2. It is the only part of the conducting system that can generate impulse.

3. It can generate the maximum number of action potentials in the conducting system.

4. It produces action potentials that are more in size than the other parts of the conducting system.

What percentage of ventricular filling is achieved by atrial contraction?

1. 30

2. 50

3. 70

4. 90

The second heart sound during the cardiac cycle is produced by the:

1. Simultaneous opening of the atrioventricular valves

2. Simultaneous closure of the atrioventricular valves

3. Simultaneous opening of the semilunar valves

4. Simultaneous closure of the semilunar valves

In a surface ECG the QRS complex represents:

1. Atrial depolarization

2. Atrial repolarization

3. Ventricular depolarization

4. Ventricular repolarization

Normal activities of the human heart are regulated:

1. Intrinsically

2. By the autonomic nervous system

3. By the brain stem

4. By the diencephalon