Human Senses: How We Perceive the World
How Do We Hear?
- An object vibrates.
- The air particles are pushed, creating sound waves.
- The outer ear picks up these vibrations and directs them to the middle ear, specifically the eardrum.
- In the middle ear, vibrations are amplified and transmitted to the inner ear.
- In the inner ear, hair cells (cilia) accumulate and transmit electrical impulses to the brain.
Diseases of the Ear
- Otitis: Inflammation of various parts of the ear, often caused by bacterial or fungal infections.
- Deafness: The diminution or loss of hearing ability.
- Dizziness: Sensitivity to motion, often experienced in cars or planes, due to excessive stimulation of the equilibrium receptors.
- Vertigo: A sensation of rotation even when stationary.
Smell
Olfactory receptors are located in the olfactory mucosa (pituitary gland), situated at the top of the nostrils. These are chemoreceptors, meaning they react to chemicals dissolved in the air.
Taste
Taste involves capturing chemical molecules dissolved in water, forming saliva. Without saliva, we wouldn’t detect these molecules. The receptors are located on the tongue and inside the mouth, in structures called taste buds. Each taste bud specializes in one of four basic tastes: bitter, sour, sweet, and salty. Taste buds are located in different areas of the tongue. The senses of taste and smell work together. Our enjoyment of many flavors is because both senses act simultaneously. This combined sensation is called flavor.
Sight
Sight is possibly the most important of our senses, as it provides most of the information we need for daily life. Light receptors are stimulated by light. These receptors are found in a very complex organ: the eye. The eye consists of the eyeball, along with muscles that provide mobility, and glands that lubricate and protect it.
The eye is composed of two parts:
- Appendages: Eyelids, eyelashes, eyebrows, and lacrimal glands. Each has a protective role.
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Eyeball:
- Sclera: The outer membrane of the eye, which becomes transparent to allow the passage of light rays, forming the cornea in the front.
- Choroid: The inner membrane, highly vascularized, with a red color. Its function is to provide nourishment to the cells of the retina.
- Iris: The pigmented portion located opposite the lens, the colored part of the eye. The black hole in the center is the pupil. Muscle fibers open or close the pupil depending on the amount of light.
- Aqueous humor: A clear fluid that fills the cavity between the cornea and the lens.
- Lens: A spherical, transparent structure located behind the cornea.
- Vitreous humor: A gelatinous fluid located between the lens and the retina in the posterior chamber.
- Retina: The innermost layer of the eye, containing light-sensitive cells: rods and cones.
How Do We See?
Light enters the eyeball through the cornea. The lens focuses the image on the retina, where the receptor cells are located. The image formed on the retina is inverted and smaller than the real object, similar to what happens inside a movie camera. The focus with which we see an object depends on how our lens focuses the image on the retina, becoming more or less curved.
Common Eye Diseases
- Myopia: The inability to focus on distant objects because the lens is too convex and cannot flatten to focus.
- Hypermetropia: The inability to focus on nearby objects because the lens is too stiff and cannot bulge.
- Presbyopia (farsightedness): Loss of visual acuity, preventing clear vision of close objects because the lens hardens and cannot change shape.
- Astigmatism: Vertical lines appear deformed because the lens bulges unevenly across its surface.
- Cataracts: The lens becomes opaque, preventing light from passing through.
- Color blindness: Certain colors, such as green and red, are confused. This is the only condition not related to the lens but to the cones.
Healthy Habits for Sense Organs
To avoid infection, we must maintain proper hygiene of our sense organs. Drugs, including alcohol, are very harmful to the health of the sense organs.
Hearing
- Avoid loud noises.
- Control the volume when listening to music or watching television.
- Speak at a lower volume than usual.
Sight
- Always read in well-lit places, preferably with natural light.
- Visit an ophthalmologist if you notice any visual abnormalities.
- Avoid blows to the eyes, the entry of foreign objects, or contact with corrosive liquids.
- Consume foods containing carotene (carrots, tomatoes). Carotene is a precursor to vitamin A, which is used to form the pigment in the retina that allows us to see.
Taste
- Brush your teeth and tongue after each meal. Poor oral hygiene results in the accumulation of substances on the taste buds, limiting their sensitivity.
Smell
- Avoid consuming toxic substances.