31 Years NEET Previous Year Questions: Body Fluids & Circulation - 2 - NEET MCQ

Antigens are foreign proteins, which stimulate specific immune response (antibody) against itself when introduced into the body. They are present on the surface of cell wall.

The pulse making impulse travels in the heart in the order of SA node→AV node→bundle of His→Purkinje fibres→heart muscles.

The leukaemia is a type of blood cancer, which is characterized by an uncontrolled increase in the number (through mitosis) of leucocytes in the blood.

Spleen and brain are the organs which receive only oxygenated blood. In gills and lungs blood picks up oxygen.

White blood cells are of two types : (i) Granulocytes (with granular cytoplasm) - neutrophils, basophils and eosinophils. (ii) Agranulocytes (with clear cytoplasm)  - Lymphocytes and monocytes

The life span of WBC ranges from 6 - 20 days, depending on the type, after which they are destroyed in the lymphatic system. When immature WBCs are first released from the bone marrow into the blood, they are called bands or stabs.

Histamine is a potant vasodilator  formed by decarboxylation of the amino acid histidine and released by mast cells in response to appropriate antigens.
Mast cells are especially prevalent in the connective tissue of the skin and respiratory tract and in surrounding blood vessels.

An adult human with average health has systolic and diastolic pressures as 120 mm Hg and 80 mm Hg respectively.

Blood group is determined by three alleles - I^A, I^B, and I^o. Alleles I^A and IB are codominant. Blood group A is determined by I^A I^A or I^A  I^o. Blood group B is I^B I^B or I^B I^o. Blood group O is I^o I^o. Blood group AB is I^A I^B.

SA is the site of generation of the rhythmic cardiac impulse. AV node is a compact mass of  myogenic fibres which receives impulse from SA node and transmits it to ventricles. Purkinje fibres are in contact with the contractile muscles of the ventricular walls. Chordae tendinae are the muscles which keep the AV valves  in position.

Arteries have thick wall and  narrow lumen while veins have thin walls and large lumen. Arteries do not have valves.

Leucocytes  are colourless, nucleated amoeboid cells found in blood which are devoid of  haemoglobin and are  capable of coming out of blood capillaries through the process of diapedesis. Fall of  WBC count is called leucopenia, and occurs due to folic acid deficiency and AIDS etc. 

Reduced protein synthesis causes thinning of hairs.

Sickle cell anaemia is a hereditary disorder of autosomal nature caused  by mutation of the gene controlling b-chain of haemoglobin. It involves substitution of glutamine by valine.

Blood group ‘O’ is known as the universal donor since it does not contain antigens.

S.A node is called the pacemaker because it initiates the cardiac impulse AV node receives the impulse from the S.A  node and transmits it to the ventricles

Lymph (called tissue fluid in the intercellular spaces) is a vascular tissue consisting of two parts-a clear, colourless fluid matrix, the plasma and floating amoeboid cells, the white blood cells, mostly lymphocytes. It differs from the blood in lacking red blood cells and some blood proteins. The lymph eventually enters the bloods near the heart.

The answer is Option C because systemic heart refers to systemic circulation of blood, which is done only through the left auricles and left ventricles combined effort.

The atrioventricular bundle (AV bundle), on entering the ventricles splits into right and left branches. These branches then enter  the heart muscles. They branch extensively and are called Purkinje fibres. They conduct the cardiac impulse to the ventricular wall. 

Blood group AB is also known as the universal recipient.

Presence of calcium will remove heparin - blood anti-coagulant and will promote blood clotting. Sodium oxalate and heparin containing test tubes will not allow the blood to clot.

SA node is the natural pacemaker located in the right atrium. SA node initiates the cardiac impulse. So, artificial pacemaker will be grafted at the site of SA node

The thymus is a major gland of our immune system. The thymus is responsible for production of T (thymus dervied) lymphocytes from immature lymphocytes, a type of white blood cells responsible for cell mediated immunity. Cell mediated immunity is extremely important for raising immune response against bacteria, yeast, fungi, parasites and virus. It is also critical in protecting against cancer, autoimmune disorders like rheumatoid arthritis, allergies etc.

• Residual capacity is that portion of air contained in the lungs which can not be expelled even by the most violent expiratory effort.
• Residual air is actually part of dead space & it doesn't play active part in respiration.
• Therefore, residual air in lungs dont affect efficiency of respiration.