The Five Senses

The Five Senses of the Body

The five senses are sight, sound, touch, taste, and smell. Each sense has its unique characteristics, organs, functions, and brain perception areas. Life without any of the five senses just wouldn't be the same.

Sight

Our sense of vision is our ability to perceive wavelengths of visible light. Light enters through the pupil and focuses through the lens. From the lens, the light is bounced to the back of the eye through the retina. Inside of the eye are cells called cones and rods. The cones and rods detect light to generate nerve impulses, which are sent straight to the brain through the optic nerve. Rods are sensitive to the brightness levels, sensing how bright or dark something is. Cones detect all the different colors that you can see. These cones or rods, called photoreceptors, work together to detect color, hue, and brightness to create a full field of vision.

Anything from severe head injuries to birth disorders can cause visual impairments. Vision is often regarded as the most dominant sense, so sight disorders can be categorized as a disability, depending on severity. A variety of conditions and factors can cause nearsightedness, which refers to being able to see things up close. Another condition is farsightedness, which means that you can see things further away. Defects in cones can result in partial or complete color blindness. People with this condition might not be able to see certain colors but still see others instead of seeing all colors as gray.

Sound

Hearing is our perception of sound, which is detected as vibrations within the ears. The mechanoreceptors in the ear perceive the vibrations, which enter the ear canal and go through the eardrum. The hammer, anvil, and stirrup aren’t tools but bones in the middle of the ear. These bones transfer the vibrations into the fluid of the inner ear. The ear part that holds the liquid is called the cochlea, which contains small hair cells that send electrical signals in response to vibrations. The signals travel through the auditory nerve directly to the brain, which determines what you are hearing.

Fg. 1 The sense of hearing. pixabay.com.

On average, people can detect sounds within a range of 20 to 20,000 Hertz. Lower frequencies can be perceived with the receptors in the ear, but higher frequencies are often unable to be perceived by animals. As you get older, your ability to hear high frequencies decreases.

Touch

Our sense of touch is called somatosensory sensation and is located around the neural receptors in the skin. Mechanoreceptors similar to those in the ears are also in the skin. These receptors sense varying amounts of pressure on the skin - from gentle brushing to firm pressing. These receptors can also sense the duration and location of the touch.

The special thing about our somatosensory perception is the variety of things we can feel. Our thermoreceptors can detect different levels of temperature. Thanks to the thermoreceptors, you don’t need to put your hand inside of fire to feel how hot it is. Our nociceptors work both in the body and the skin to sense pain. All three of these receptors travel through the peripheral to the central nervous system arriving in the brain.

Taste

Taste can be one of the most pleasant senses to experience, but it also helps keep us safe. Our taste buds not only tell you if something tastes good or not but also if the food contains minerals or dangerous substances, such as poison. The taste buds can detect five basic tastes: sweet, bitter, salty, sour, and umami. Receptors for these five tastes are found in distinct cells on all tongue areas.

Fg. 2 Taste, pixabay.com.

One thing to keep in mind is that the flavor of food is not the same as the sense of taste. The flavor of something you eat combines taste, temperature, smell, and texture. The taste buds react to chemicals in foods and create neural impulses, which are sent to the brain.

Smell

Our olfactory sense, or sense of smell, works very closely with our sense of taste. Chemicals and minerals from food, or ones just floating in the air, are perceived by the olfactory receptors in our nose that send the signals to the olfactory bulb and olfactory cortex. There are over 300 different receptors in the nose, each with a specific molecule detector. Every smell is made up of combinations of specific molecules, and they bind to different receptors at different strengths. Chocolate cake will smell very sweet, maybe a tiny bit bitter, and a little bit of a whole lot of different scents. Unlike the other receptors, olfactory nerves regularly die and regenerate throughout our lifetimes.

The Five Sense Organs and Their Functions

So, how exactly do we get the information from our senses to our brain? Our nervous system takes care of that for us.

When we take in stimuli, such as looking at a picture or smelling some flowers, it gets converted into an electric signal sent through our brain. The smallest amount of stimuli needed for the sensation to happen is called the absolute threshold. For instance, you might not be able to taste a single tiny grain of salt in a meal because the absolute threshold is higher than that. If you added much more salt, it would pass the threshold, and you would be able to taste it.

Our absolute threshold connects to Weber's law, which helps you see if you can notice differences in our environments.

The factor that affects the process of interpreting stimuli is signal detection. The different receptors receive their own form of stimuli, which travels via different processes to be interpreted by the brain. Sensory adaptation is what happens when these receptors lose sensitivity due to changes in the environment. This is how you are able to see better in the dark once you've been there for a few minutes.

Chemical Senses

Taste and smell, otherwise known as gustation and olfaction, are called chemical senses. All of the senses get information from stimuli, but chemical senses get their stimuli in the form of chemical molecules. The process in which we perceive both smell and taste involves energy transduction and specialized pathways in the brain. It sounds complicated, but we pretty much have miniature chemical reactions to be able to smell and taste things.

Body Senses

The body senses of kinesthesis and the vestibular sense provide information about the position of your body parts and your body movements within your environment. Kinesthesis is the system that enables you to sense the position and movement of individual parts of your body. Sensory receptors for kinesthesis are nerve endings in your muscles, tendons, and joints. Your vestibular sense is your sense of balance or body orientation.

Information Obtained From the Five Senses

Let's break down this transduction thing a little bit more. We have our chemical senses and our body senses, but we also have a variety of energy transduction processes. Each of the five senses includes one or more types of energy transduction.

Energy can come in a wide range of types, some of which we experience daily and others that we rarely come into contact with:

• Kinetic

• Sound

• Chemical

• Electrical

• Light

• Heat

• Nuclear

• Magnetic

• Gravitational potential

• Elastic potential

So, how do we experience these types of energy? We feel kinetic and heat energy with our sense of touch. We see the light and hear sound. As mentioned earlier, our taste and smell senses involve chemical energy.

Anatomical Structures for the Senses

Our sense of touch is straightforward: we feel things by touching them with our skin. We can also feel our receptors in muscles, tendons, joints, and ligaments, but most of our information comes from our skin. For hearing, our entire ear is involved in making sure that we can take in sound and know where it comes from. Sensory receptors in our eye are the photoreceptors we talked about earlier, which are kept in the retina. The sensory neurons connect to the central nervous system directly from the eye.

Our nose has two parts: the nostrils and the nasal canal. The nostrils are the two external openings of the nose, whereas the canal extends to the back of the throat. Within the canal is the mucous membrane, which has many smell receptors within it. The olfactory nerve sends the information from the membrane to the brain.

Did you know that there can be anywhere from 10 to 50 gustatory receptors per taste bud? There can be 5 to 1,000 taste buds per pore. If you crunch the numbers, that is a lot of receptors in the tongue. However, not all of them are for taste. Many of the receptors are for touch, pain, and temperature.

The Five Senses and Perception

The five senses help a person create an objective perception of reality. The senses are crucial in letting us process information from our environment. They work as physiological tools of sensation that allow our brain to perform perception. Hearing, in particular, enables us to distinguish languages, sounds, and voices. Taste and smell give us important information for recognizing the properties of a substance.

How do all of our five senses work together? Sense perception is our understanding or interpretation of what we are sensing. We learn what things sound like, look like, and more as we perceive more of the world.

According to Gestalt psychology, we understand things visually as patterns or groups, rather than just a bunch of individual things. This also means that we can make connections between our sensory input and our cognitions.