Question 1

The straw-coloured, fluid matrix of blood (about 55% of blood volume) is called:

Accepted Answer

Plasma. Plasma is the liquid part of blood (~55%); serum is plasma without clotting factors.

Question 2

The most abundant plasma protein, responsible for maintaining osmotic balance, is:

Accepted Answer

Albumin. Albumins maintain the osmotic (oncotic) pressure; globulins are for defence and fibrinogen for clotting.

Question 3

The most abundant blood cells, which carry oxygen and lack a nucleus in humans, are the:

Accepted Answer

Erythrocytes (RBCs). RBCs (~5 million/mm³) are enucleate, biconcave and packed with haemoglobin for O₂ transport.

Question 4

A person with blood group AB is called a universal ______ because:

Accepted Answer

Recipient; plasma has no anti-A or anti-B antibodies. AB individuals lack anti-A/anti-B antibodies, so can receive any ABO type — universal recipients.

Question 5

The human heart is ______ chambered, with two atria and two ventricles:

Accepted Answer

Four. The human heart has four chambers — two atria (upper) and two ventricles (lower).

Question 6

The pacemaker of the heart, which initiates the heartbeat, is the:

Accepted Answer

Sino-atrial node (SAN). The SA node in the right atrium sets the rhythm — hence "pacemaker".

Question 7

The volume of blood pumped out by one ventricle in one heartbeat is the:

Accepted Answer

Stroke volume. Stroke volume (~70 mL) is the blood ejected per beat by a ventricle.

Question 8

In an ECG, the ______ wave represents the depolarisation of the ventricles:

Accepted Answer

QRS complex. The QRS complex marks ventricular depolarisation (leading to contraction).

Question 9

Persistently high blood pressure (e.g. above 140/90 mmHg) is called:

Accepted Answer

Hypertension. Hypertension is high blood pressure (normal ≈ 120/80 mmHg), a major risk factor for heart disease.

Question 10

Chest pain due to insufficient oxygen reaching the heart muscle is called:

Accepted Answer

Angina (pectoris). Angina pectoris is acute chest pain from inadequate oxygen supply to the myocardium.

Question 11

Serum differs from plasma in that serum:

Accepted Answer

Lacks clotting factors (fibrinogen). Serum = plasma minus the clotting proteins (fibrinogen and others consumed during clotting).

Question 12

Plasma without formed elements contains ~90–92% water and important ions including:

Accepted Answer

Na⁺, Ca²⁺, Mg²⁺, HCO₃⁻ and Cl⁻. Plasma carries minerals (Na⁺, Ca²⁺, Mg²⁺, bicarbonate, chloride), glucose, amino acids, lipids and proteins.

Question 13

Erythroblastosis foetalis occurs when:

Accepted Answer

An Rh⁻ mother carries an Rh⁺ foetus and her anti-Rh antibodies attack the foetal RBCs. In a second Rh⁺ pregnancy, maternal anti-Rh antibodies cross the placenta and destroy foetal RBCs.

Question 14

The formed elements of blood are produced (haematopoiesis) mainly in the ______ in adults:

Accepted Answer

Red bone marrow. In adults, red bone marrow is the main site of blood cell formation.

Question 15

The correct path of the electrical impulse in the heart is:

Accepted Answer

SA node → AV node → bundle of His → Purkinje fibres. The impulse spreads SAN → AVN → bundle of His → its branches → Purkinje fibres, contracting the ventricles.

Question 16

The vena cava carries ______ blood to the ______, while the pulmonary vein carries ______ blood to the ______:

Accepted Answer

Deoxygenated; right atrium; oxygenated; left atrium. Venae cavae bring deoxygenated blood to the right atrium; pulmonary veins bring oxygenated blood to the left atrium.

Question 17

The first heart sound "lubb" is produced by the closure of the ______ valves at the start of ventricular systole:

Accepted Answer

Atrioventricular (bicuspid and tricuspid). "Lubb" (S1) = closure of AV valves (systole begins); "dup" (S2) = closure of semilunar valves (systole ends).

Question 18

If a person has a heart rate of 75 beats/min and a stroke volume of 70 mL, the cardiac output is:

Accepted Answer

5.25 L/min. CO = 75 × 70 = 5250 mL/min = 5.25 L/min.

Question 19

A "heart attack" (myocardial infarction) occurs when:

Accepted Answer

Blood supply to a part of the heart muscle is blocked, causing muscle death. A blocked coronary artery deprives cardiac muscle of oxygen, causing its death (infarction).

Question 20

The normal human blood pressure is about ______; the higher value represents ______ pressure:

Accepted Answer

120/80 mmHg; systolic. Normal BP ≈ 120/80 mmHg — 120 (systolic, ventricular contraction) over 80 (diastolic, relaxation).

Body Fluids and Circulation — NEET Biology MCQs with Solutions

Subtopics

Sample questions with solutions