Senses: eyes and ears Lesson 69 of the biology course of Mova's primary school: 15 sentences, each with its syntax tree and pragmatics. The lessons are written for Mova, and their agreed trees are part of Mova corpus 0.4 (CC BY-SA 4.0). How Mova does on its tests: the lesson at school .
0 Your eyes catch light and your ears catch vibrations in the air, and both turn what they catch into nerve signals that the brain makes into pictures and sounds. 1 Walk out of a dark cinema into bright sunshine and you squint: the black dot in your eye, the pupil, shrinks fast, because the coloured ring around it, the iris, is a muscle that lets in less light. 2 Inside the eye a lens, like a magnifying glass, throws an upside-down picture onto the back of the eye, and the brain turns it the right way up and even fills in a small blind spot where you see nothing at all. 5 The pupil is a hole that lets light into the eye; the coloured iris around it is a muscle that makes the pupil smaller in bright light and bigger in the dark. 6 The lens in the eye works like a magnifying glass and makes an upside-down picture on the retina at the back of the eye, and the brain turns it the right way up. 7 Where the optic nerve leaves the eye there are no light cells, so each eye has a small blind spot that the brain usually fills in so we do not notice it. 8 Cone cells for colour come in three kinds, most sensitive to red, green and blue light, and the brain mixes their signals into all colours; rod cells see in dim light but not in colour. 9 About 1 in 12 boys and men and about 1 in 200 girls and women are colour blind, most often mixing up reds and greens. 11 Carrots have vitamin A, which the eye needs to see in dim light, but eating extra carrots does not give night vision; the story spread in the Second World War and, many historians say, helped hide the use of radar. 12 Bats are not blind: all bats can see, and many also find insects in the dark by echolocation, making high squeaks and listening for the echoes. 13 Sound is vibration in the air: it shakes the eardrum, three tiny bones called the hammer, anvil and stirrup pass it on, and hair cells in the snail-shaped cochlea turn it into nerve signals. 14 Sound reaches the nearer ear a tiny fraction of a second sooner and a little louder, and the brain uses these differences to tell where a sound comes from. 15 The inner ear has three loops filled with fluid; when you spin, the fluid swirls, and after you stop it keeps moving for a moment, so you feel dizzy. 16 Very loud sounds can damage the hair cells in the cochlea, which in people do not grow back; ringing ears after fireworks are a warning sign, and ear defenders help. 17 An echo is sound bouncing off a hard surface and coming back; sound travels about 340 metres a second in air, so an echo from a cliff 170 metres away comes back after about one second. ← previous The brain and nervesnext → Senses: nose, tongue and skin↑ back to Biology This page in Markdown → https://md.mova.elamur.ai/free/en/corpora/school/biology/69-senses-eyes-and-ears/