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

A decrease in plasma albumin levels is likely to affect:

1. Clot formation

2. Oxygenation of hemoglobin

3. Osmotic balance

4. Immune functions

There is a possibility of exposure of the maternal blood [of Rh -ve mother] to small amounts of Rh +ve blood from the fetus during the:

1. First trimester of any pregnancy

2. Third trimester of the second pregnancy only

3. Delivery of the child

4. There is no such possibility

Congestion of the lungs is one of the main symptoms in:

1.  Hypotension

2.  Coronary artery disease

3.  Angina

4.  Heart failure

The right atria of the human heart receive:
1. Oxygenated blood
2. Deoxygenated blood
3. Arterial blood
4. Venous blood

The following is the diagrammatic representation of standard ECG. Identify the correct statement :