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This blog post is part of this year’s summer series called Brain Basics, in which we dive into the general functions and development of our brains.
Our senses ensure that we are in contact with the world. The five basic senses: sight, hearing, smell, taste, and touch are the gateways through which we experience our environment. In this blog post, we explore how these senses work.
Sight: the perception of light
Vision begins with light received by various types of nerve endings (receptors) in the retina of our eyes called rods and cones. Thanks to different types of cones, which respond to blue, red, or yellow-green light, we can perceive different colors. Color blindness can be caused by abnormalities in these cones. Rods are sensitive to the intensity of light and have no color preference. For example, nocturnal animals have more rods, which makes them see better in low light.
Cones and rods convert light into electrical signals, which are sent to the visual cortex (cerebral cortex in the occipital lobe). These signals are interpreted as visual information, such as shapes, colors, and movements. This is passed on to other brain areas that determine what you see, like the area sensitive to faces. Other areas determine where the things that you see are located.
Hearing: the perception of vibration
Sounds are vibrations in the air. These are also called sound waves. These waves are picked up by the eardrum, which sets tiny bones in the middle ear in motion. The cochlea, a spiral shape in the inner ear, contains hair cells that convert this movement into electrical signals. These signals are transported to the auditory cortex via the auditory nerve and processed into sound information. Different areas then determine where the sound is coming from and what it means.
Smell and taste: the gourmets of all molecules
Smell
We are able to smell things thanks to the receptors at the top of the nasal cavity. These receptors respond to inhaled molecules that evaporate from a substance and float through the air as a gas. Electrical signals are carried to the olfactory bulb in the brain via the olfactory nerve. Here, the signals are interpreted as different smells. The olfactory bulb of many animals is larger and more sensitive than that of humans (think about drug detection dogs).
Taste
Taste is a response to molecules in your mouth: the taste buds on your tongue activate taste receptors. The receptors then send electrical signals to the taste areas in the insular cortex, where they are interpreted as sweet, sour, salty, bitter, and umami. Our sense of taste is supported by our sense of smell thanks to molecules ascending through the nose and throat connection. That is why we cannot taste well when that cavity is clogged during a cold!
Touch: tactile sense
Our skin contains several receptors that can sense pressure, temperature, and pain. When we touch something, these nerve endings send electrical signals to the somatosensory cortex, where they are interpreted as your soft stuffed animal, a hot coffee mug, or a painful Lego brick under your foot. We prefer not to feel pain, but that is precisely the benefit, it is a warning that we receive in the event of (imminent) tissue damage: “Watch out, this rose bush stings!”.
Perception is subjective
The way we experience the world is influenced by more than just our senses. Our perceptions are filtered by the limits of our sensational abilities and are colored by what we learn about the world. You can see this, for example, in (visual) illusions. But whether it’s the most beautiful art or a pot of hot soup, it’s our senses that make sure we perceive it
In the upcoming posts of this series, we’ll dive further into the anatomy, the development, and the different functions of our brains.
Credits
Author: Maartje Koot
Buddy: Marlijn ter Bekke
Editor: Judith Scholing
Translation: Helena Olraun
Editor translation: Ping Chen
Featured image from Nathan Bingle via Unsplash