Locust Fork High students smell and taste rosemary from their sensory garden after reading Shakespeare's Ophelia.

Investigate Your Senses


Humans have five basic senses that help send information to our brain so we can understand the world around us. 

These senses help us to know what is safe or unsafe, what we like and don’t like, and observe what’s happening around us.

Scientists are great at using their senses to improve their observation skills!
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Click on the senses below to learn more about them!
Click on the bat to learn about other animals' special senses!

 

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Sight
Why do we see?
In many ways, sight is the dominant or most important sense to humans. Our eyes are much more complicated than those of most other animals. While most animals get information about their environment through their sense of smell, we get most of ours from our sight.
For example, you have probably seen your dog with his nose to the ground, sniffing and moving along in the direction of what smells most interesting. Humans don’t do that. We follow what we can see! Your dog could smell all of the wildlife that visited your yard, but we could not. We could see all the wildlife in vivid color, but your dog could not.
How do we see?
Light reflects off of an object to our eyes. Light passes through the cornea (the clear front layer of the eye). Some of this light enters the eye through the pupil (the black part of the eye). The colored part of the eye, or the iris, control how much light comes in through the pupil. The light then passes through the lens which focuses the light on the retina. The retina is a layer of tissue at the back of the eye that has special cells that turn the light into electrical signals. Those electrical signals then travel from the retina to the brain through the optic nerve. Your brain turns those signals into the images you see!	Click on image to enlarge it

  
 

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Hearing
Why do we hear?
Hearing is very important to humans as it is allows us to communicate with one another. Activist and educator Helen Keller once said, “Blindness cuts us off from things, but deafness cuts us off from people”. Our sense of hearing helps us in other ways as well – experiencing the world around us (music, television, bird calls, etc.) and staying safe (smoke detectors and other alarms, car horns, etc).	American Robin singing  Josh Madison Click on image to enlarge it
How do we hear?
The human ear is very complex. It is broken down into three main parts called the outer (or external) ear, middle ear, and inner ear. Sounds move through these parts in an organized manner that allows us to hear the world around us.
Sound is funneled from the outside to your outer ear through the ear canal of your middle ear. The sounds move through your ear canal to the eardrum, making it vibrate. The vibrations pass to three tiny bones behind the eardrum – the malleus, incus, and stapes. The vibrations then pass from the bones to the cochlea in your inner ear. Tiny hair cells within the cochlea pick up the vibrations which are then turned into electrical signals.   These electrical signals are sent to the brain through the auditory nerve.	Click on image to enlarge it

   
  

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Touch
Why do we feel (touch)?
We experience pressure, temperature, vibration, pain, and other sensations through our skin. This tells us when something is hot or cold, smooth or bumpy, and everything in between. Do we need to let go? Hold on? Squeeze tighter? All of this is based on what we feel and how our brain reacts to it. Not only does our sense of touch tell us, for example, that someone has tapped us on the shoulder, but also which shoulder was tapped and which direction in which to turn around and look.
How do we feel (touch)?
Our skin has many types of receptors, or structures that help us get information from the environment around us. Receptors are very small but collect very detailed information when touched. Different kinds of receptors respond to different kinds of information. This helps our bodies understand fully what is touching our skin! Some of these receptors are near the surface of the skin while some are buried deeper.
Thermoreceptors sense temperature. In colder temperatures, thermoreceptors that sense cold are most active. In warmer temperatures, thermoreceptors that sense heat are most active.  Nociceptors sense pain. They detect damage to skin cells.  Mechanoreceptors simply sense contact with the skin. There are 4 types of mechanoreceptors:	Click on image to enlarge it
Merkel: Nerve endings that respond to light and middle levels of pressure – like pressing your finger to your lips. They also respond to slow vibrations. They are located near the skin’s surface.  Meissner: Nerve endings that respond to very light touch – like being tickled with a feather. They are located just below the top layer of skin. Ruffini: Nerve endings that are sensitive to being stretched or squeezed. They also respond to changes in temperature. Pacinian: Nerve endings that are sensitive to all kinds of vibrations as well as deep and prolonged pressure. They are the deepest and largest receptors in our skin.
When the receptors are activated, they send signals to your nervous system – either to your brain or spinal cord. Then the brain tells the body how to respond. Some parts of the body have more receptors than other parts. Areas with more receptors are more sensitive. For instance, your fingertips and forehead have lots of receptors, as they are used to explore the world around us, but your calf or back have less receptors since they are not as important for exploring the world around us.

 

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Smell
Why do we smell?
Some scientists say that humans may be able to smell over 1 trillion scents!! Throughout time we have learned to recognize things as good or bad based on how the smell. For example, milk is stinky when it goes bad. Because it is stinky, we don't drink it and we don't get sick! There are exceptions to this, of course, but in general we use our sense of smell to better understand things around us. Smelling is also important to tasting.
How do we smell?
We have millions of specialized sensory cells on a small patch of tissue high inside our noses. These cells, called olfactory sensory neurons, are connected directly to the brain and each has one odor receptor.     When molecules, or tiny parts, from things around us (like flowers or food) make their way to the odor receptors, signals travel from the olfactory nerve to the olfactory bulb. From the bulb, messages are sent to the brain and the smell is identified.	Click on image to enlarge it
These molecules can reach the receptors through two routes: your nostrils or through chewing. There is a channel that connects the roof of the throat to the nose and when you chew, odor molecules are released. This is why smell and taste are so closely related! When you have a cold and your nose is stuffy and you lose the ability for odors to reach the receptors through breathing, tastes aren’t as strong. While we can indeed taste without smelling, we get taste more fully when we also smell our food.

 

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Taste
Why do we taste?
Taste is a very important sense and has been throughout time. Early on, before we had fast food and grocery stores, it helped us to survive in the wild by teaching us what was safe to eat. A bitter or sour taste meant that something could be poisonous or rotten. A sweet or salty taste typically meant that it was rich in nutrients.
How do we taste?
Taste is a combination of:     The taste we experience from our mouths (gustatory), the smell experienced by our nose (olfactory), and the touch experienced with our hands. We are able to recognize five different tastes – sweet, sour, salty, bitter, and savory (or umami). These tastes are sensed in the taste buds. While most taste buds are on the tongue, some line the epiglottis (back of the throat), the nasal cavity (in your nose), and the esophagus (connects the throat to the stomach).
We are born with about 10,000 taste buds but start to lose them around 50-60 years of age. All 5 tastes can be sensed by taste buds on all parts of the tongue. The sides of the tongue are more sensitive than the middle. About half of the cells in taste buds react to several of the 5 tastes. The other half are specialized to react to only one taste.     Taste buds have sensory cells that form capsules containing tiny hairs (microvilli).  These hairs are responsible for collecting chemical information about what you’re eating and send a message to the brain through the afferent nerves about how what you're eating tastes.	Click on image to enlarge it

 

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Do Other Animals Sense Things the Same Way We Do?
Most animals do not have noses, eyes, hands, mouths, and ears like ours. Does that mean they don’t have the same senses we do? No! They just experience them in different ways. They face different challenges in their lives than we do, and have adapted to survive better in their habitats because of that. Check out this list of some of the wacky ways other animals’ senses work!
Click image to enlarge it	Bats use echolocation to find food. This is the use of high-pitched pulses of sound and listening for the return of the pulse. They are able to determine distance and direction of objects in their environment this way. They can actually find food, like small insects, up to 18 feet away!
Bees have several special senses! They have taste receptors on their jaws, legs, and antennae. Their vision is different than ours in that they have the ability to see the ultraviolet spectrum! This means they can see colors that we cannot – and flowers have patterns (called nectar guides) on them that only they can see. Bees have to process a lot of information to navigate and pollinate, but they do not have large brains to do it. Instead, they have a small ring of magnetic particles inside of their abdomen that can detect the magnetic field of the Earth. This helps bees define their location – sort of like the GPS that guides you in your car.		Humans see yellow, bees see nectar guides. Bjorn Roslett Click image to enlarge it
Monarch touching leaf with feet PIXNIO	Butterflies have taste receptors on their feet. They use this to detect whether or not a plant is poisonous. They lay their eggs on the underside of leaves and the caterpillars that hatch out will eat the leaves – so a poisonous plant would kill the caterpillars!
Catfish have taste buds all over their bodies – they are basically just long, slimy tongues! While humans have up to 10,000 taste buds on their tongues, catfish have over 175,000 taste buds all over their body. They typically live in really dark, muddy places, and don’t have great eyesight. The taste buds help detect prey in these conditions by tasting what is around them as water flows over them.		Catfish in dark water Wikimedia
Dog reacting to hearing whistle Wikimedia	Dogs can hear sounds as high as 40,000 Hz – humans can only hear up to 20,000 Hz. This is what allows them to hear high-pitched sounds like dog whistles while we cannot!
Earthworms’ entire bodies are covered with taste receptors. They use these to smell the air and their potential food sources.		Worm in dirt Pixabay
Fly on food Flickr - Simon Berry	Flies have sensory hairs on their lips and their feet. This means that when they land on your food, they’re actually tasting it! And if they like what they taste, then they will use their mouthparts to consume it.
Eagles (and other birds of prey) have 2-4 times better visual acuity, or sharpness of vision, than humans because they many more nerves in their eyes than we do – this means more information is sent from the eye to the brain! Normal vision for humans is 20/20; eagles (and other birds of prey) is 20/5. This means that they can see from 20 feet what most people can see from 5 feet!		Immature Bald Eagle Flickr - DCSL
Diagram of snake sensory organs Wikimedia Click image to enlarge it	Snakes have nostrils, but they don’t use them like we do for smelling. Instead, they use their forked tongues! They collect scent molecules from the air when their tongues are out of their mouths. Then, when the snake pulls its tongue back inside its mouth, those molecules are to its “sensory center” (called the Jacobson’s organ) through the roof of its mouth, then to the brain through nerves connecting the two. The tongue can even help it figure out where its prey is located. Just by flicking its tongue outside of its mouth, it can determine whether the prey is to the right or left.
Vultures can see small rodents from a height of 15,000 feet – that’s as tall as the Empire State Building!		Turkey vulture in flight Pixabay

   

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