Atria can completely empty during ventricular filling due to:
1. A-V node
2. A-V bundle
3. S-A node
4. Purkinje fibers

The period that extends from the onset of atrial depolarization until the onset of ventricular depolarization is shown in an ECG as:
1. QRS complex
2. S-T interval
3. P-Q interval
4. QRS-T interval

The arrhythmia that results in cardiac arrest followed by death in the absence of treatment and therefore considered most serious is:
1. Tachycardia
2. Sinus bradycardia
3. Atrial flutter
4. Ventricular fibrillation

The venous return to the heart is facilitated by:
1. valves
2. inspiration
3. skeletal muscle
4. all of these

A condition where the arteries become narrowed and hardened due to a buildup of plaque around the artery wall is called as:
1. arteriosclerosis
2. phlebitis
3. atherosclerosis
4. plaque

During the cardiac cycle the tricuspid and bicuspid valves get closed when:
1. when pressure inside the ventricles is at its lowest
2. when pressure inside the atria is greater than that inside the ventricles
3. when ventricular pressure exceeds that of the atria
4. when pressure is greater in the aorta than in the left ventricle

A large bone marrow cell with a lobated nucleus responsible for the production of blood thrombocytes is:
1. progranulocyte
2. basophilic band cell
3. monoblast
4. megakaryoblast

The least significant factor for erythropoiesis amongst the following is:
1. vitamin B₁₂
2. vitamin B₆
3. folic acid
4. gastric intrinsic factor

A disease state in which the hematocrit (the volume percentage of red blood cells in the blood) is elevated is called as:
1. polycythemia
2. anemia
3. leukemia
4. porphyria

The deficiency of cynocobalamin or vitamin B12 causes: