The five senses of the human being

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Living beings and man among them have mechanisms designed to capture the variations that occur in the environment and respond correctly to them. The five senses of the human being fulfill this function: sight, hearing, touch, taste and smell. These senses have specialized cells with receptors that are activated by specific stimuli, connected through the nervous system to the brain.

In this lesson from unPROFESOR.com we are going to explain what are the five senses of the human being and its functions.

Index

1. The sense of sight
2. The sense of hearing
3. Sense of touch
4. Smell
5. The sense of taste

Of the five senses of the human being, sight and hearing are key since they provide us with fundamental information about what happens in our environment, allowing our body to react in the most appropriate way.

The eye is the dominant sense organ and on which the sense ofsight, It provides the brain with more information than all the other senses put together. It is located in the eye socket and depends on the optic nerve, which contains one million nerve fibers. The

Three-dimensional or stereoscopic vision is very important for measuring distances and calculating the speed at which objects are traveling. The eyes contain fluids (aqueous and vitreous humor) and alongside them there are other attached organs: eyebrows, eyelids, tear glands and eyelashes.

In the structure of the eyeball three membranes are distinguished:

• Sclera: outer area of ​​the eye, white in color, formed by a fibrous tissue that goes from the cornea up to the optic nerve.
• Choroid: dark layer that is located under the sclera. Behind the cornea, the choroid is replaced by the iris, which is a muscular disc in charge of controlling the opening of the orifice of the pupil. The iris is characterized by having a different color in each person and is made up of muscle fibers whose contraction allows the pupil to open or close. Behind this is the crystalline, a transparent organ shaped like a lens.
• Retina: light-sensitive layer that covers the eye. It contains nerve fibers and specialized cells: cones (6 to 7 million, work in bright light) and rods (about 125 million, to see in low light).

To look in different directions without moving the head, the eye can rotate its orbit through a complex group of eye muscles. Vision occurs when light passes through the clear cornea and enters the pupil. The iris acts like a diaphragm and regulates the amount of light that enters. Images are formed in the retina, thanks to the crystalline lens, which acts as a lens that focuses on objects.

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Within the five senses of the human being we also have to speak of the ear. In addition to providing the hearing, the ears they detect the position and movement of the head and are essential for balance. They have two elements, one mechanical and the other related to electrical nerve impulses, and they are divided into three parts:

• External ear: composed of the ear or pinna and the external auditory canal.
• Middle ear: cavity within the temporal bone. In this three holes stand out: an external one, which closes the eardrum; another internal one, denominated oval window, that communicates with the inner ear; and, finally, a lower one, which corresponds to the Eustachian tube.
• Inner ear: set of ducts made up of the semicircular canals and the snail, being its interior filled with liquids called perilymph Y endolymph.

The ears They act as energy converters by transforming air pressure differences into electromagnetic nerve impulses. The brain is responsible for interpreting these electrical impulses and converting them into information. Also in the inner ear there are organs related to balance, which allow us to stand upright and recover when we are about to fall, in addition to being able to turn our heads and bend down without losing our stability.

The sense of touch it has an eminently exploratory character. Its operation is due to small sensory receptors found in the skin, with different shapes and sizes. These localize stimuli, such as heat, cold or pain, and send their signals from the spinal cord and lower brain to the somatosensory cortex.

There are five types of sensory receptors: cold, heat, pain, pressure, and touch. The thermoreceptors they correspond to cold and heat, the former being more abundant; those of pain are the nociceptors, that are related to very intense chemical, mechanical and thermal stimuli that generate tissue damage; and, finally, those of pressure and contact are the mechanoreceptors, which are found mainly on the lips, the skin of the back and the fingertips.

The sense of smell It is located in the olfactory epithelium, a tissue that is in the roof of the nasal cavity and that locates the molecules that are in the air. Substances that have an odor give off molecules, which appear in the air and are inhaled. These dissolve in the nasal mucosa and stimulate the olfactory nerve. The information travels to the olfactory lobes of the brain and also to a primitive region of the brain, the rhinencephalon or also called the limbic system.

When we eat food, we use both the sense of smell like that of taste, Since when chewing a large number of volatile molecules are released, exciting the olfactory cells of the nasal cavity.

And we end this lesson with the five senses of the human being to talk about the sense of taste that has a function similar to smell. In the taste buds its receptor cells are found, which detect substances that dissolve in saliva. The tongue could distinguish four basic tastes: sweet, sour, salty and bitter. Its surface is covered with small extensions called papillae, which contain the nerve endings that capture taste.

The taste buds They are stimulated by food particles that dissolve in saliva. Nerve impulses travel to the brain through the facial muscles and the nerveglossopharyngeal. The sense of taste fulfills the important function of stimulating the stomach glands by making gastric juice, which is used to digest food.

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