Uttar Pradesh 2017 Previous Year GK Questions with Answers

The correct answer is B, the brain. The brain is the organ that interprets pain, but its own tissue has no pain receptors, so cutting or pricking it causes no sensation; the covering membranes, the blood vessels and the scalp do have receptors, which is why a headache hurts. This is the reason brain surgery can be performed on a patient who is awake and talking, with only the scalp anaesthetised. Option A is wrong because the skin is the richest field of pain receptors in the body and a needle prick there is the standard example of a painful stimulus. Option C is wrong because the heart has pain receptors and signals its distress as the crushing pain of angina, often felt in the left arm as referred pain. Option D is wrong because the cornea of the eye is among the most sensitive tissues of the body, which is why the smallest speck of dust in it is unbearable.

The correct answer is A, Ant. Among the four, the ant has the largest brain in proportion to its body. An ant’s brain is tiny in absolute terms, with about two hundred and fifty thousand neurons, yet it makes up roughly a sixth of the insect’s body weight, a share no vertebrate comes close to. This is a general rule of body size: as animals get smaller, the brain shrinks more slowly than the body, so small creatures carry proportionately bigger brains. Option B is wrong because an elephant has the largest brain in absolute weight on land, about five kilograms, but that is a very small fraction of a body of several tonnes. Option C is wrong because a dolphin, though highly intelligent, has a brain near one per cent of its body weight. Option D is wrong because a human brain is about 1.4 kilograms, roughly two per cent of body weight, high for a vertebrate but far below an ant’s share. Exam tip: elephant biggest brain by weight, ant biggest in proportion.