Sensory organs: functions and receptors

The human sensory organs: functions and receptors represent a specialized peripheral anatomical-physiological system.
Hee that ensures the acquisition and primary analysis of information from the surrounding environment. As well as from other organs of the organism itself, thanks to their receptors.

They collect data from both the external and internal environments of the body.

Humans perceive information through five main sensory organs:

👁️ Eyes (sight)
👂 Ears (hearing)
👅 Tongue (taste)
👃 Nose (smell)
✋ Skin (touch, pain sensation, temperature)

However, many scientists believe that the human sensory organs: functions and receptors encompass eight or even more types of sense. As additional perceptions such as motion detection, balance, and temperature sensation can be included. Furthermore, many internal organs in our body also contain receptors that, for example, can regulate the sensation of thirst.

🔍 Which of the senses is the most important?

Undoubtedly, it is the eye. Approximately 70% of information comes through it. The eye consists of a lens that functions as a biological lens, focusing on light. The lens is surrounded by muscles that can change its curvature, ensuring sharp vision.

Is the opening in the iris – the pupil of the eye, regulates the amount of light entering by expanding or contracting.

On the retina of the eye, light is converted into nerve impulses that are transmitted to the brain, allowing us to see. Like any lens, the lens inverts the image, and the processing and flipping of the picture occur in our brain.

Why don’t our eyes dry out?

This happens thanks to the tear fluid produced by a gland located in the eye socket. When the cornea of the eye is at risk of drying out, a signal is sent to the corresponding part of the brain, activating a reflex: the upper eyelid quickly closes. At this moment, a small amount of tear fluid is distributed over the cornea, moisturizing it.

Why do tears taste salty?

Salts are present in all biological fluids of the body, such as blood, saliva, and sweat. The salt content in these fluids is approximately the same. Additionally, tear fluid contains proteins and the enzyme lysozyme, which serve a protective function for the eyes, preventing infections.

Why do we sometimes feel “sand” in our eyes after sleeping?

What we clean from the corners of our eyes in the morning is not actually sand, but dried tear fluid. Its composition includes not only water but also salts, proteins, and fats. When the eyes are closed, tear fluid is not secreted, which can lead to the formation of small yellow particles. Fats and proteins mixed with a small amount of salts are the reason for the appearance of this “sleepy sand.”

Why do we sometimes have sparks in our eyes?

Sensitive cells of the visual system primarily respond to the flow of light; however, they can also be excited by other stimuli if they are sufficiently intense. A blow to the head or eye can trigger an excessive reaction in these sensitive cells. Since these cells can only transmit signals to the brain in the form of light stimuli, more optical phenomena occur than usual. It is at this moment that we may see sparks in our eyes.

Does reading in poor lighting harm the eyes?

When we read in the evening twilight, our eyes have to strain to recognize the letters. This can lead to headaches. Scientists still do not have a definitive answer to the question of whether reading can cause myopia (nearsightedness), which is a vision disorder characterized by distorted sharpness of distant images, while nearby objects are seen clearly. However, it is likely that insufficient lighting increases this probability. Therefore, it is recommended to read in proper lighting.

Do individuals with color blindness see everything in black and white?

Yes, that is correct. Fortunately, only a small number of people actually suffer from color blindness, which is a disorder that affects the ability to distinguish colors. Approximately 30,000 individuals have color blindness. Since the cones in the retina responsible for color perception do not function properly, these individuals perceive the surrounding world in black and white. Some of them claim to be color blind; however, they usually cannot identify specific colors. They most often confuse red and green. Individuals with this disorder cannot perform certain professions, such as working as firefighters or drivers.

What are contact lenses?

Contact lenses are specialized devices for vision correction, for which this technology was developed. The idea of using contact correction was first proposed by Leonardo da Vinci in 1508. In the archive of his works, there is a drawing of an eye that includes a water bath, which is a precursor to modern contact lenses. The introduction of lenses into medical practice was carried out by the German inventor August Müller. Today, there are also decorative lenses that are used to change the color of the eyes and even the shape of the pupil. Both corrective and decorative lenses are made from special materials and are placed directly on the surface of the eye. Currently, about 125 million people worldwide use contact lenses. The method of vision correction using contact lenses is called contact vision correction.

Sensory organs: functions and receptors. Interesting Aspects of Hearing

We often do not realize how certain sounds can bring us joy. When we dance to our favorite music, listen to the sound of the waves, or hear the voices of our loved ones, it spontaneously brings a smile to our faces. We take hearing for granted, yet it is a complex system that needs to be preserved.

Our ears, like our noses, continue to grow throughout our lives, and the left ear may differ from the right in both external and internal structure.

Women have a more sensitive perception of sound than men, while men are better at determining the location and direction of sounds.

The human ear is capable of perceiving sounds only within certain frequencies. Signals that fall below the hearing range are called infrasound, while those above are referred to as ultrasound.

In the same individual, each ear may perceive sounds differently. When processing auditory information, the right ear transmits information to the left hemisphere of the brain, and vice versa.

Human ears and more the functions

Human ears also serve the function of dissipating excess heat from the body into the surrounding environment. As a result, the size of ears may vary among people from different climatic zones (generally, those from southern regions have larger ears).

Absolute pitch is determined by the perception of information by brain centers rather than the condition of the ears. Regardless of hearing acuity, a person can distinguish several sounds simultaneously.

A person becomes aware of a sound 35-175 milliseconds after it reaches the ear. Additionally, about 180-500 milliseconds are needed to “tune in” for optimal sound perception.

On both sides of the ears are special canals that help us maintain balance and orient ourselves in space.

Teenagers have a better ability to perceive high-frequency signals than adults and the elderly.

We perceive our own voice through layers of air and water, which is why our perception of it differs from what others hear. For them, the sound is clearer.

When we hold a seashell to our ear and hear the sound of the waves, it is actually the sound of blood circulating through our veins.

The tradition of wearing earrings originated with sailors who wished to be buried beautifully after death.

Causes of Hearing Loss

Hearing loss can occur as a result of exposure to sounds of certain loudness, which create a powerful impulse in the hair cells located in the inner ear. These cells lose their ability to adequately perceive sounds. In most cases, their function is restored over time. However, prolonged exposure to loud sounds can lead to irreversible changes. In such cases, the hair cells lose the ability to convert sound signals into nerve impulses, which are transmitted to the auditory nerve, and then to the brain.

Tinnitus

The sensation of ringing, buzzing, hissing, or humming in the ears is called tinnitus. It is not a separate disease but a symptom that can have several causes, such as inflammation, allergies, or the presence of earwax. In some cases, the noise can be so intense that it causes insomnia. Any sensation of noise in the ear lasting more than one day is a reason to consult a doctor.

Why Can Some People Move Their Ears?

Sometimes, one can observe certain animals, such as cats and foxes, moving their ears while standing still. This movement of the ear flaps in different directions allows them to pick up faint sounds, which helps in hunting or avoiding danger. It is suggested that human ancestors also had the ability to move their ears, as this could have contributed to their survival while fleeing from predators or during hunting. In some people, this ability has been preserved to this day.

Human Senses: Functions and Receptors – Our Nose

The nose serves not only the function of perceiving smells but also has important tasks. These include warming, moisturizing, and filtering the air we breathe before it enters the lungs. The inner part of the nose is lined with a mucous membrane that contains microscopic cilia, which constantly move from the throat to the nostrils, performing between 450 to 900 movements per minute. These cilia, made up of ciliated epithelium, trap dust, dirt, and bacteria, pushing them outwards. As a result, particles accumulate in the front part of the nose, which we remove using a tissue or our fingers. The sticky secretions from the nose are a mixture of nasal mucus and impurities.

How do we perceive smells?

Smells are formed by molecules that detach from the surfaces of objects and spread through the air. When we inhale, these molecules reach the olfactory receptors, of which there are about 3 million. Each receptor specializes in a specific aromatic substance. When a smell molecule contacts a receptor, a nerve impulse is generated in the cell and transmitted to the brain. A person can distinguish up to 10,000 different smells.

Why do we need two nostrils?

The air streams we inhale through the nostrils converge in the trachea. At first glance, it seems that one nostril would be sufficient. However, scientists have not yet been able to definitively explain this mystery. There is a hypothesis that during breathing, the nostrils function alternately, which may allow the olfactory cells to rest. However, this remains just a hypothesis.

Why do we sneeze?

Sneezing is a protective reflex that occurs when the mucous membrane of the nose is irritated, for example, by viruses, pollen, dust, or fumes. During a sneeze, air is expelled from the lungs through the trachea and out of the nose. This activates all the facial muscles, and the facial nerve also participates in this process, responsible for the automatic closing of the eyes.

Human sensory organs: functions and receptors – the tongue

The human tongue is made up of striated muscle tissue and is covered by a mucous membrane. When the muscles contract, its shape changes. The tongue performs important functions in the processes of chewing, clear speech, and taste perception. The role of the tongue is especially important during the sucking of the mother’s milk by infants and young children. Lips securing it the child’s grasp the nipple. The soft palate rises to close the throat, while the tongue acts as a piston, moving backward and creating negative pressure along with the lowering jaw. After this, the jaw rises, and the alveolar arches compress the nipple, facilitating the swallowing of milk. Therefore, the infant’s tongue is relatively large, thick, and wide, occupying the entire oral cavity, while being relatively immobile.

On the surface of the tongue, there are special taste buds that are responsible for perceiving different tastes. These tastes are:

• salty,
• sweet,
• sour,
• bitter.

The flavors of food

Thanks to these buds, we can distinguish the flavors of food.

The tip of the tongue is more sensitive to sweetness, the sides are more sensitive to sour and salty, while the base is more sensitive to bitterness.

The tongue is the only muscle in the human body that is attached on only one side.

Appearance and the color of the tongue can reveal a lot about a person’s health.

The tongue contains between 2,000 to 10,000 taste receptors, which are renewed approximately every 14 days.

Can distinguish four basic types of tastes: salty, sour, sweet, and bitter. Recently, a fifth taste known as umami has been discovered, which is associated with protein substances such as parmesan and meat.

By the age of 60, most people lose about half of their taste receptors, leading to changes in taste perception.

To detect taste, the tongue must be moist. If a piece of lemon is placed on a dry tongue. The brain will not receive any signal about the taste.

No two tongues are the same; the imprint of each person’s tongue is unique, similar to fingerprints.

Women tend to have a greater number of taste receptors compared to men.

Injuries to the tongue heal significantly faster than injuries to other parts of the body.

Human Senses and Their Functions: Skin

The outer covering of an animal organism is the skin, which serves the function of protecting the body from various external influences. It also participates in processes of respiration, thermoregulation, metabolism, and many other functions.

Human skin has a multilayered structure. The outer layer, known as the epidermis, consists of numerous cells that are renewed approximately every four weeks. Old cells are shed in the form of tiny flakes. Due to the constant regeneration of cells, the skin is capable of healing from scratches and other injuries. The epidermis contains sebaceous and sweat glands, which help maintain the skin’s elasticity. Beneath the epidermis lies the dermis, or true skin, which contains nerves, blood vessels, and muscle fibers. This layer also houses hair follicles. Below the dermis is another layer made up of connective and adipose tissue, which acts as a cushioning layer that protects internal organs from impacts and cold.

What functions does the skin perform?

The skin performs numerous important functions, among which protection is one of the most significant. This can be easily demonstrated by the example. After a fall, the tissue under the abrasion remains intact. Additionally, the skin is an organ that contains a large number of sensitive cells, allowing us to feel heat and cold. As well as determine the texture of objects—whether they are soft or hard. The skin is also capable of distinguishing between pleasant and unpleasant touches. Furthermore, through sweat glands, the skin protects the body from overheating.

Why are there people with different skin colors?

Skin color is inherited from parents. It is determined by the concentration of the pigment melanin, which directly depends on the intensity of sunlight exposure. In Africa, where the sun shines brightly throughout the year, the local population has evolved to have darker skin. A high concentration of melanin provides protection against harmful sun rays. In northern regions, where the sun is active only in the summer, a lighter skin type has developed over centuries.

Why do we tan?

Natural skin pigments contain melanins, which absorb ultraviolet rays, protecting the body’s tissues. When a person is exposed to the sun, melanins are produced in the skin, leading to skin darkening. However, prolonged sun exposure can result in sunburn. Lighter skin is more sensitive to ultraviolet radiation.

Sun rays can harm the skin and eyes. Excessive ultraviolet exposure can lead to conjunctivitis and sunburn. This is accompanied by redness, increased temperature, and sensitivity. The danger of sunburn lies in the dehydration of all structures, which can lead to cataracts, impaired vision, and melanoma.

Sun protection:

Snow and sand have the ability to reflect sunlight. Therefore, when skiing or spending time at the beach, it is extremely important to use sunglasses and high SPF sunscreen (at least 30). At the beach, it is recommended to wear a wide-brimmed hat. On extremely hot days, from 11:00 AM to 3:00 PM, it is advisable to stay in the shade. During this period, the sun’s rays are particularly dangerous.

Who are albinos?

You may have repeatedly observed animals with white fur and red eyes. They suffer from a hereditary condition known as albinism. This condition is also present in humans. Individuals with albinism have a lack of pigment in their skin, hair, and the iris of the eye. Pigments are colored substances that are part of the body’s tissues. Most albinos also face vision problems. Albinism is incurable, so individuals suffering from this condition must take extra care to protect their skin.

What are the dangers of moles?

Moles (nevi) are usually not dangerous. They can be congenital or develop over time. The number of depends on the duration and frequency of a person’s sun exposure. The problem is that under the influence of sunlight, moles can sometimes change color, shape, and size. Some of these changes can be malignant. The more moles there are, the higher the risk of transformation. Therefore, it is important to regularly monitor moles and undergo examinations by a dermatologist, a skin disease specialist.

Why do older people develop wrinkles?

Despite the fact that the skin is regularly renewed. It begins to age from the age of 25. It becomes drier and less elastic. The lower layer of the skin, which consists of fatty tissue, becomes thinner, causing the upper layer to lose its firmness. This leads to the appearance of wrinkles, which deepen with age. Expression lines occur due to the frequent contraction of certain facial muscles. For example, when a person furrows their brow or squints. Additionally, folds around the eyes and mouth form when a person laughs often. These folds give the face more expressiveness.

Why do teenagers often get acne during puberty?

During adolescence, there is a surge of sex hormones in teenagers. The hormone responsible for acne is testosterone, along with some others. Testosterone stimulates the sebaceous glands to produce excess sebum. If the ducts of the glands are clogged, sebum accumulates, creating a favorable environment for microorganisms. Acne most commonly affects the face, neck, upper chest, and back. Areas where sebaceous glands are most abundant.

Why do we get goosebumps from the cold?

Our body is covered with numerous fine hairs. Muscles attached to the follicles of these hairs are responsible for raising them. When a person feels anger or excitement, as well as in cold conditions. These muscles activate, causing the hairs to stand up. As a result, small bumps form on the skin, known as goosebumps.

Why do sweaters cause discomfort?

Some sweaters made from natural wool can leave uncomfortable sensations on the skin. This is due to the structure of wool fibers, which are similar to human hairs. Each fiber is surrounded by a layer of scales. When these scales do not lie flat and stick out in different directions. They can irritate the skin. Sweater manufacturers usually try to use wool from animals whose scales lie closely together. The smoother the structure of the wool fibers, the higher the cost of the sweater. However, such products do not cause discomfort.