Zoology MCQs for NEET — Practice Questions with Answers

(a) 'Bundle of His' is a part of heart in humans. The bundle of His is an important part of the electrical conduction system of the heart, as it transmits impulses from the atrioventricular node, located at the inferior end of the interatrial septum, to the ventricles of the heart.

Deficiency of vitamin B₁₂(cobalamine) and folate can result in megaloblastic anaemia. This type of anaemina may be accompanied with ineffective erythropoiesis. Neurological abnormalities are peculiar symptom of the disease. The vitamins are intertwined biochemically so that the final common pathway that impairs DNA synthesis in hematopoietic cells.

Folic acid  (Vit B9) is essential for formation of RBCs and deficiency causes megablastic anaemia, abnormal immature RBCs by bone marrow.

Cyanocobalamin (Vit B12) is essential for RBCs production, DNA synthesis, proper functioning of neurological system its deficiency causes pernicious anaemia. 

(b) Ductus arteriosus is a channel of communication between the main pulmonary artery and the aorta of the foetus that allows much of the blood from the right ventricle to bypass the foetus fluid filled lungs. During foetal development, this protects the lungs from being overworked and allow the right ventricle to strengthen.

(d) Christmas factor is the plasma thromboplastin component i.e., thromboplastin activator present in blood plasma. Factor IX is synthesized in liver with the help of vitamin K. It causes congenital disorder, haemophilia B (also called christmas disease). This disease is sex linked recessive and determined by distinct gene from the sequence involved in the commoner haemophilia A in which deficiency of factor VIII occurs.

(a) Folic acid is erythrocyte maturing factor. Folic acid is a water-soluble vitamin that is important in red blood cell formation, protein metabolism, growth and cell division. Folic Acid has been shown to work together with vitamin B₆ and vitamin B₁₂ to reduce blood levels of homocysteine, an amino acid that builds and maintains tissues. Folic acid also works closely together with vitamin B₁₂ to regulate the formation of red blood cells and to help iron function properly in the body.

(b) : Normal blood sugar level in adult human varies from 80-100 mg/100 ml (fasting) to 100-120 mg/100 ml (after meal).

Normal blood urea is 20-40 mg/dl

Total blood volume is 4-5 litres

ESR in wintrobe method is 0-9 mm in male and

0-20 mm in female.

(a) : The gradually increasing contraction of ventricular muscles during systole first causes the
closure of bicuspid and tricuspid valves (AV valves), producing a low-pitched "lubb" sound. Later, it causes the opening of the semilunar valves of systemic and pulmonary aorta. At the end of ventricular systole, scmilunar valvcs shut, producing the sccond, louder heart sound, the "dup". Thus each heart beat is accompanied by a "lubb-dup" sound

(d)  Heparin prevents blood coagulation in the blood vessels. It is secreted by mast cells. It is an anticoagulant, blocking conversion of prothrombin to thrombin. Haemoglobin is the blood pigment necessary for oxygen transport. Plasma is the component of blood. Thrombin is the product of blood clotting.

(a) Thickening of arteries due to cholesterol deposition is arteriosclerosis. This is extremely widespread disease predisposes to myocardial infarction, cerebral thrombosis and other serious illness. It is characterized by infiltration of cholesterol and appearance of foam cells in certain lesions of arterial wall, distorting the vessels and making them rigid.

(d) Haemophilia B is due to deficiency of factor IX (Christmas factor). The patient may experience prolonged bleeding following any injury or wound, and in severe cases there is spontaneous bleeding into muscles and joints.