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The Human Body: Nervous System - Sense Organs and their care

Grade 5ICSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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The sense organs are specialized organs that help us perceive the world around us. They are connected to the brain through the network of the Nervous System.

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The Eye: Light enters through the transparent cornea, passes through the pupil, and is focused by the lens onto the retina. The image formed is sent to the brain via the Optic Nerve.

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The Ear: Sound vibrations travel through the outer ear and ear canal to the eardrum. These vibrations move the small bones in the middle ear and are converted into signals in the cochlea, which travel via the Auditory Nerve.

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The Nose: The upper part of the nasal cavity contains olfactory receptors. When we breathe in, chemical molecules dissolve in mucus and trigger the olfactory nerves to send smell signals to the brain.

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The Tongue: It contains tiny bumps called papillae which house taste buds. The four basic tastes recognized are sweet, sour, salty, and bitter.

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The Skin: The largest sense organ of the human body. It contains nerve endings sensitive to pressure, pain, heat, and cold. It helps in maintaining body temperature, often around 37∘C37^{\circ} C.

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Care of Sense Organs: Includes avoiding sharp objects in ears, reading in proper light (avoiding glare), cleaning the tongue with a cleaner, and protecting skin from extreme UVUV radiation.

📐Formulae

Vision Flow:Light→Cornea→Pupil→Lens→Retina→Optic Nerve\text{Vision Flow}: \text{Light} \rightarrow \text{Cornea} \rightarrow \text{Pupil} \rightarrow \text{Lens} \rightarrow \text{Retina} \rightarrow \text{Optic Nerve}

Hearing Flow:Sound Waves→Ear Canal→Eardrum→Cochlea→Auditory Nerve\text{Hearing Flow}: \text{Sound Waves} \rightarrow \text{Ear Canal} \rightarrow \text{Eardrum} \rightarrow \text{Cochlea} \rightarrow \text{Auditory Nerve}

TCelsius=59(TFahrenheit−32)T_{Celsius} = \frac{5}{9}(T_{Fahrenheit} - 32)

💡Examples

Problem 1:

Why is it difficult to taste food when you have a severe cold and a blocked nose?

Solution:

Flavor is a combination of both taste and smell.

Explanation:

The tongue only senses basic tastes like sweet or salty. The 'flavor' of food comes largely from the olfactory receptors in the nose. When the nose is blocked, the CO2CO_2 and aroma molecules cannot reach the olfactory nerves, making the food taste bland.

Problem 2:

Calculate the distance a student should maintain from a book while reading to avoid eye strain, if the recommended distance is approximately 2525 cm. Express this in meters.

Solution:

0.250.25 m

Explanation:

Since 100 cm=1 m100 \text{ cm} = 1 \text{ m}, then 25 cm=25100 m=0.25 m25 \text{ cm} = \frac{25}{100} \text{ m} = 0.25 \text{ m}. Reading too closely causes the ciliary muscles in the eye to overwork.

Problem 3:

Which part of the eye acts like a camera film where the image is formed?

Solution:

The Retina

Explanation:

The Retina is the light-sensitive innermost layer of the eye. When light rays are focused by the lens, an inverted image is formed on the retina, similar to how an image is captured on a camera film or digital sensor.

Sense Organs and their care - Revision Notes & Key Formulas | ICSE Class 5 Science