Human Physiology Questions and Answers

Answer: B

A, B and C can be Thyroid, Adrenal glands, Pituitary.

The pituitary is the 'master gland': its hormones regulate other endocrine glands. Thyroid-stimulating hormone (TSH) makes the thyroid release thyroxine, and adrenocorticotropic hormone (ACTH) makes the adrenal cortex release its hormones.

The thyroid does not give orders to other glands, so every option naming it as gland C is wrong. Option 4 reverses the relationship by having the pituitary take orders from the thyroid.

Answer: C

The answer is 2 hours.

The figure comes from the NCERT Class V Environmental Studies chapter 'From Tasting to Digesting'. It draws on the observations the army surgeon William Beaumont made on a man with a permanent opening in his stomach, which gave the time different foods stay in the stomach before they are digested. In that table boiled milk takes about 2 hours, and unboiled milk a little longer, 2 hours 15 minutes.

The options 3, 4 and 5 hours are not the NCERT figure for boiled milk; a figure of about 3 hours appears in a different study of raw milk and is not in the NCERT table. I checked the figure against secondary pages that reproduce the table, not the textbook itself.

Answer: D

(A), (B), (C) are Thyroxine, Thyroid, Iodine.

Thyroxine, secreted by the thyroid gland, regulates the metabolism of carbohydrates, proteins and fats. The thyroid needs iodine to make thyroxine, so a diet lacking iodine leads to goitre, a swelling of the gland.

Growth hormone mainly controls growth, insulin regulates blood sugar, and adrenaline prepares the body for emergencies; none matches all three blanks.

Answer: C

The true statements are (A), (C) and (D).

Whales and dolphins are mammals: they breathe air through nostrils, the blowholes on top of the head, and must come to the surface regularly to breathe. They cannot use the oxygen dissolved in water.

They have lungs, not gills, so (B) is false, and every option containing (B) is wrong.

This is why whales and dolphins can drown if they are trapped underwater, unlike fish, which take oxygen from the water through their gills.

Answer: D

Both (A) and (B) are true.

Bile, made by the liver and stored in the gall bladder, makes the acidic food coming from the stomach alkaline so that pancreatic enzymes can act. It also breaks fat into small droplets (emulsification), which helps in the digestion of fats.

Bile has no digestive enzymes, but both of its roles described here are correct, so options rejecting either statement are wrong.

Answer: D

(A) is true and (R) is false.

Arteries carry blood away from the heart under high pressure, so they have thick, elastic walls to withstand it.

(R) has it the wrong way round: blood pressure is high in arteries and low in veins, which is why veins have thinner walls and valves to stop backflow.

The difference in wall thickness follows directly from this: thick, muscular, elastic arterial walls absorb each surge of blood pumped by the heart and keep it flowing between beats.

Answer: B

The statement that is not true is Endocrine glands secrete hormones through ducts.

Endocrine glands are ductless glands. They release their hormones directly into the blood, which carries them to target organs. Glands that pour their secretions through ducts, such as salivary and sweat glands, are exocrine glands.

The other statements are true. The pancreas (which secretes insulin) and the adrenal glands are endocrine glands. The pituitary gland is attached to the base of the brain. Endocrine glands secrete hormones.

Answer: C

Metamorphosis in frogs is controlled by Thyroxine.

Thyroxine, the hormone of the thyroid gland, triggers the change from tadpole to adult frog. If the water lacks iodine, which the thyroid needs to make thyroxine, tadpoles fail to change into adults; in experiments, adding thyroxine speeds up the change.

Adrenaline prepares the body for emergencies. Growth hormone from the pituitary controls growth in size. Insulin from the pancreas controls blood sugar. None of them drives metamorphosis.

Answer: C

Diabetes is controlled by insulin.

Insulin is secreted by the beta cells of the islets of Langerhans in the pancreas. It lowers the blood sugar level by helping cells take up glucose and by promoting its storage as glycogen. When insulin is deficient or ineffective, blood sugar rises: this is diabetes mellitus.

Thyroxine controls metabolic rate, adrenaline prepares the body for emergencies (and raises blood sugar), and thymosin, from the thymus, helps develop immunity.

Answer: D

The correct statements are (i) and (ii).

William Beaumont, an American army surgeon, studied digestion through a wound in the stomach of Alexis St. Martin that never fully closed after a gunshot accident in 1822. Through it he observed that the stomach churns food and digests it with juices it secretes, so (i) and (ii) are true. This story appears in the NCERT Class V EVS book.

Statement (iii) is false: Beaumont found that the gastric juice is acidic, not basic; it contains hydrochloric acid. Statement (iv) overstates the time: his experiments ran from 1825 to 1833, well under ten years, not nineteen. Every option including (iii) or (iv) is therefore wrong.