NDA Human body systems previous year questions with solutions

Answer: (c) Sphincter muscle

Method. Pyloric sphincter

The exit of food from the stomach is regulated by a sphincter muscle which releases it into the small intestine in small amounts (C5-A37).

Answer: (a) pH 2.0 and 7.9, respectively

Method. Optimum pH of pepsin and trypsin

Pepsin acts in the acidic medium of the stomach at about pH 2 (C5-A35); trypsin of the pancreatic juice acts in the alkaline small intestine at about pH 8 (C5-A39, C5-A40, C5-A42). Only (a) has acid for pepsin and alkaline for trypsin; (d) wrongly gives a neutral pH for pepsin.

Answer: (c) Secretion of lipase, amylase and protease

Method. Pancreatic enzymes

The pancreas secretes pancreatic juice with lipase, amylase and protease (trypsin) (C5-A42). Breaking up lipid droplets is by bile salts from the liver, bile is stored in the gall bladder, and neutralising acid is by bile (C5-A40).

Answer: (b) bile and lipase

Method. Fat digestion by bile and lipase

Bile salts emulsify large fat globules into smaller ones, and lipase of the pancreatic juice then breaks down the emulsified fat (C5-A40, C5-A41, C5-A42). Trypsin and pepsin digest proteins and amylase digests starch.

Answer: (c) pepsin

Method. Pepsin is the gastric protease

The gastric glands of the stomach wall release pepsin, a protein-digesting enzyme (C5-A34). Trypsin is secreted by the pancreas (C5-A42), amylase digests starch and chitinase digests chitin.

Answer: (d) bile juice

Method. Bile makes the chyme alkaline

Bile juice from the liver makes the acidic food coming from the stomach alkaline so the pancreatic enzymes can act (C5-A40). This is the NCERT wording of the stem. Pancreatic juice is also alkaline and the nearest wrong option, but the Class 10 text names bile for this role; the option set has one answer in that reading.

Answer: (a) Protein only

Method. Gastric acid activates pepsin

The acid-secreting (parietal) cells make HCl, which gives the acidic medium pepsin needs (C5-A34, C5-A35); without it protein digestion in the stomach fails. Carbohydrate digestion in the stomach is negligible (salivary amylase is stopped by acid), so carbohydrates are not affected in the same way; so (a), not (d).

Answer: (c) I and III

Method. statement analysis of animal respiration

I is true: glycolysis is cytoplasmic in all cells, aerobic or not (C5-A48). II is false: aerobic gives far more energy (C5-A52). III is true for animals: their anaerobic path ends in lactic acid (C5-A53), so CO2 comes only from aerobic respiration. The CO2 of fermentation (C5-A50) is yeast, not animals. Hence I and III.

Statement III is true only because the stem restricts to animals; yeast fermentation releases CO2 anaerobically.

Answer: (d) I, II and III

Method. Adaptations of the alveoli

The alveoli are the surface for gas exchange, with an extensive net of blood capillaries around them (C5-A63) and a very thin epithelium for fast diffusion; the elastic fibres of the wall let them expand and recoil with each breath. All three help, so (d). Elastic fibres help ventilation rather than diffusion.

Answer: (b) Bronchi of humans

Method. Gas exchange sites

Gas exchange occurs in the skin of earthworms, the gills of Pila and the alveoli of humans (C5-A63). The bronchi are only air passages that lead to the alveoli (C5-A117). Negative stem.

Answer: (b) Tidal volume

Method. Lung volumes compared

Typical values: tidal volume about 500 mL, expiratory reserve about 1000-1100 mL, residual about 1100-1200 mL, inspiratory reserve about 2500-3000 mL (C5-A65 for the residual volume). The tidal volume is the lowest. Standard result, Class 11 Biology.

Answer: (b) Tidal volume

Method. Tidal volume

The volume of air breathed in or out in a normal breath, about 500 mL, is the tidal volume. Vital capacity is the maximum breathed out after a maximum breathing in. Standard result, Class 11 Biology (lung volumes and capacities); no row in the Class 10 set.

Answer: (b) Bowman’s capsule

Method. Parts of the respiratory tract

Trachea and bronchi are air passages and the diaphragm drives inhalation (C5-A64, C5-A117). Bowman's capsule is part of the nephron of the kidney (C5-A101), so it takes no part in breathing. Negative stem: the answer is the part that does NOT help.

Answer: (b) Semilunar valve

Method. Semilunar valves

The pulmonary valve at the opening of the right ventricle into the pulmonary artery is a semilunar valve (C5-A74, C5-A76). The tricuspid valve is between the right atrium and ventricle; the bicuspid or mitral valve is between the left atrium and ventricle. Standard result, Class 11 Biology.

Answer: (b) Pulmonary arteries always carry oxygenated blood while Pulmonary veins always carry deoxygenated blood

Method. Arteries and veins; find the false statement

Statement (b) is reversed: the pulmonary artery carries deoxygenated blood to the lungs and the pulmonary veins carry oxygenated blood back to the left atrium (C5-A73, C5-A74, C5-A116). (a), (c) and (d) are true (C5-A82). Negative stem.

Answer: (b) Fibrinogen

Method. Fibrinogen forms fibrin in clotting

Fibrinogen is the soluble plasma clotting protein that is converted into insoluble fibrin threads; platelets help to clot blood at the injury (C5-A84). A pathogen is a germ, macrophages and phagocytes are white blood cells. Standard result, Class 11 Biology (body fluids).

Answer: (d) plasma

Method. Lymph resembles plasma

Lymph or tissue fluid is similar to plasma but colourless and with fewer proteins (C5-A85).

Answer: (d) Electrocardiogram is graphical representation of electrical activity of heart

Method. ECG records the heart

An electrocardiogram records the electrical activity of the heart. The brain is recorded by an EEG. Standard result, Class 11 Biology (circulation).

Answer: (a) left auricle

Method. Path of blood through the heart

Oxygen-rich blood from the lungs enters the left atrium (auricle) through the pulmonary veins (C5-A73); the right auricle receives deoxygenated blood from the body (C5-A74).

Answer: (a) no nucleus, no mitochondria and no endoplasmic reticulum

Method. Structure of the mammalian red blood cell

Mature human RBCs lose the nucleus, mitochondria and endoplasmic reticulum, leaving room for haemoglobin; they get energy by glycolysis alone. Only (a) says all three are absent. Standard result (Class 11 Biology); no NCERT row for it in the Class 10 set.

Answer: (d) Bowman’s capsule

Method. Bowman's capsule filters

The basic filtration unit is the nephron: the glomerulus within the cup-shaped Bowman's capsule filters the blood (C5-A101). The collecting duct receives the filtrate from the tubule, the ureter carries urine (C5-A104) and the renal vein carries blood away.

Answer: (a) Renin

Method. Renin-angiotensin system

Juxtaglomerular cells of the kidney secrete the enzyme renin, which converts the plasma protein angiotensinogen into angiotensin I; nitrogenase is a bacterial enzyme of nitrogen fixation, hydrolase and mono-oxygenase are enzyme classes, not this enzyme. Standard result (Class 11 Biology); no NCERT row for it in the Class 10 set.

Answer: (c) Corpus callosum

Method. Parts of the hind-brain

The hind-brain consists of the pons, the medulla and the cerebellum (C6-A17, C6-A64). The corpus callosum is a band of nerve fibres joining the two cerebral hemispheres of the fore-brain. Negative stem.

Answer: (a) Involuntary actions such as blood pressure, salivation vomiting etc.

Method. Medulla of the hind-brain

Involuntary actions such as blood pressure, salivation and vomiting are controlled by the medulla in the hind-brain (C6-A22). Sensory regions and the hunger centre belong to the fore-brain (C6-A18, C6-A20). Option (c) is the nearest wrong one: voluntary movements are decided in the fore-brain, and the cerebellum only makes them precise (C6-A23).

Answer: (d) sodium and potassium

Method. Na+ and K+ carry the impulse

The impulse in a nerve cell is carried by movement of Na+ and K+ ions across the membrane (Class 11 Biology, neural control). Keyed by the options: sodium alone and potassium alone are each only half the mechanism; iron plays no part. So (d).

Answer: (b) cochlea

Method. Cochlea transduces sound

The cochlea of the inner ear converts the pressure variations of sound into electrical (nerve) signals; the auditory nerve only carries them to the brain, the eardrum vibrates and the eustachian tube equalises pressure. Standard result, Class 11 Biology (neural control, the ear).

Answer: (d) is composed of proteins and cells.

Method. Structure of the cornea

The cornea is a transparent layer of cells and protein (collagen) with no blood vessels. The light sensitive screen is the retina and the muscular diaphragm is the iris, so (a), (b) and (c) are wrong. Standard result, Class 10 Science, human eye.

Answer: (b) cornea

Method. Light enters through the cornea

Light enters the eye through the transparent cornea; the pupil is the opening in the iris and the retina is the screen at the back. Standard result, Class 10 Science, human eye; no assertion row for it in the Class 10 set listed.

Answer: (c) retina

Method. Image forms on the retina

The retina is the light-sensitive screen at the back of the eye on which the image forms; the cornea and the lens refract the light, the iris controls the pupil. Standard result, Class 10 Science, human eye.

Answer: (b) Receptor—sensory neuron—spinal cord—motor neuron—effector

Method. Order of a reflex arc

Receptor, sensory neuron, spinal cord, motor neuron, effector (C6-A11, C6-A12, C6-A63). Option (c) routes through the brain, which a reflex arc bypasses, since it is formed in the spinal cord.

Answer: (b) Sodium

Method. Sodium ions carry the nerve impulse

The nerve impulse is carried by movement of Na+ (and K+) across the neuron membrane (Class 11 Biology, neural control). Of the elements offered only sodium is a biological ion; lithium, rubidium and caesium play no part in nerve conduction. Keyed by the options: sodium is the only one present among them.

Answer: (a) Ultraviolet radiation

Method. Melanin absorbs ultraviolet

Melanin in skin, hair and iris absorbs ultraviolet radiation and so protects the DNA of skin cells from damage. Standard result, Class 11 Biology.

Answer: (b) Cones

Method. Cones give colour vision

Cones, concentrated at the fovea, respond to bright light and distinguish colours; rods work in dim light. The blind spot and fovea are regions of the retina, not photoreceptor cell types. Standard result, Class 11 Biology (sense organs: the eye).

Answer: (b) Monkeys

Method. Oestrus cycle versus menstrual cycle

Cows, rats and tigers show an oestrus cycle (female receptive only at heat), but primates such as monkeys have the menstrual cycle. Negative stem. Standard result, Class 11 Biology.

Answer: (b) Primary spermatocyte

Method. Meiosis I in spermatogenesis

The primary spermatocyte (2n) undergoes the first meiotic division, forming two secondary spermatocytes (n), which divide in meiosis II into spermatids. The spermatogonium divides by mitosis; the Sertoli cell is a supporting cell. Standard result, Class 11 Biology.

Answer: (c) Ovary and pituitary gland

Method. Menstrual cycle hormones

The menstrual cycle is regulated by ovarian hormones (oestrogen and progesterone) under the control of the pituitary hormones (FSH and LH). Standard result, Class 11 Biology (reproductive health); the Class 10 set gives only the cycle itself (C7-A67, C7-A71).

Answer: (d) Adrenaline

Method. Adrenaline speeds the heart

Adrenaline is secreted from the adrenal glands into the blood and makes the heart beat faster (C6-A47, C6-A48). Insulin regulates blood sugar and melatonin the sleep rhythm; thyroxine raises metabolic rate, not as the direct emergency heart hormone.

Answer: (d) They inhibit the release of egg.

Method. Oral pills stop ovulation

Oral contraceptives change the hormonal balance so that eggs are not released and fertilisation cannot occur (C7-A76). They do not kill the egg, sperm or zygote.

Answer: (b) Estrogen

Method. Oestrogen in females

At puberty oestrogen brings about the changes in appearance in females (C6-A53). Prolactin acts on milk production, oxytocin on birth and milk ejection, progesterone prepares and maintains the uterine lining. Standard result.

Answer: (a) Cervix

Method. Male reproductive parts

The urethra, seminal vesicle and vas deferens belong to the male system; the cervix is the neck of the uterus in the female (C7-A64). Negative stem.

Answer: (c) controls metabolic rate.

Method. Thyroxine controls metabolic rate

Thyroxine from the thyroid regulates the metabolic rate of the body. Blood glucose is controlled by insulin (C6-A54), ovulation and pregnancy by ovarian and pituitary hormones. Standard result, Class 11 Biology (endocrine system).

Answer: (c) Bronchiole

Method. Cartilage in the respiratory tract

The nose, the trachea (C-shaped rings) and the knee joint (articular cartilage, menisci) contain cartilage; the bronchioles are narrow tubes of smooth muscle without cartilage. Negative stem. Standard result, Class 11 Biology.

Answer: (d) urinary bladder

Method. Where cartilage occurs

Cartilage supports the larynx, nose and external ear. The wall of the urinary bladder is smooth muscle with no cartilage (C5-A104). Negative stem. Standard result, Class 11 Biology (connective tissue).

Answer: (d) Calcium phosphate

Method. Enamel is calcium phosphate

Tooth enamel is hydroxyapatite, a form of calcium phosphate, the hardest substance in the body. Standard result, Class 11 Biology; C5-A47 shows enamel is softened and demineralised by acid.

Answer: (b) Collagen

Method. Tendon is made of collagen

Tendons are dense bundles of collagen, a tough fibrous protein; elastin is the stretchy protein of ligaments and arteries, fibrin forms blood clots, cellulose is a plant carbohydrate, not a protein. Standard result, Class 11 Biology (connective tissue).