Introduction to Special Senses: Study with Video Lessons, Practice Problems & Examples

The special senses include vision, smell (olfaction), taste (gustation), hearing, and equilibrium, each linked to specific organs. Vision relies on the eyes to detect electromagnetic radiation (light), while smell and taste measure chemical properties, allowing us to perceive a vast array of odors and five basic tastes: sweet, sour, salty, bitter, and umami. Hearing involves the cochlea detecting pressure waves, and equilibrium is managed by the semicircular canals, sensing movement and gravity. Understanding the distinction between stimuli and perception enhances comprehension of these senses.

Special Senses

Hello, and welcome to your special senses. Alright. Before we dive into the special senses, let's just remember that there are actually 2 types of senses, 2 general categories that we break things into. We have the general senses. These are things distributed throughout your body, and you've probably already learned about these, things like temperature, pain, pressure, things you can feel in your feet, your hands, your back, wherever. What we're talking about here are our special senses, and these are located in special sense organs. And all those special sense organs, they're in your head. Alright. We're going to say that there are 5 special sense organs, and we'll go through each one here. As we do, I want you to pay particular attention to the stimulus that's in the environment that these organs measure, and then how we perceive that stimulus. Because those two things aren't the same. And being able to link them, but also being able to tell what the difference between the two is, I think really helps us understand what special senses are doing and how they work. Alright. To see what I mean, let's start with vision. Now vision, the organ that does that, I bet you know, it's your eyes. And to illustrate that, we have a cross-section of an eyeball right here. What the eye is measuring is electromagnetic radiation or what we call light. But I think it's important to remember that there's nothing fundamentally different between light and other types of electromagnetic radiation, things like x-rays or radio waves. What allows us to call light light is that our eye is able to sense those wavelengths of electromagnetic radiation. And when it does, we see a couple of things. We see brightness which is the intensity of the radiation that's hitting our eyes, and color. And color is a measure of the wavelength of light that's actually coming into our eye. Alright. Next, let's talk about smell. Smell, also called olfaction, we use our olfactory epithelium to do that. And here we see someone smelling, we see a cross-section of the nasal cavity here and molecules are coming up into the nasal cavity. And we can see at the top there is the olfactory epithelium connected to the olfactory bulb inside the skull. And what smell is measuring is something about chemical properties, and when we measure those chemical properties, well, we perceive them as odors. Now kind of amazingly, we can distinguish something like a trillion different odors, which completely blows my mind. But what you're doing when you're doing that is you are identifying different molecules that are in the air or different combinations of molecules that are in the air. That brings us to our sense of taste, also called gustation, which in some ways is going to be similar to our sense of smell. For taste, we use our taste buds, and here we have a diagram of a tongue here because that's where the vast majority of our taste buds are located, and here we are also measuring the chemical properties. But here we're measuring chemical properties of things we put in our mouth or usually our food, but it's going to work very differently. Where we could distinguish a trillion different odors, here, we get 5 tastes. We get sweet, sour, salty, bitter, and umami. And umami, you may not be familiar with; it's a taste that sort of savory taste that's associated with sensing amino acids in your food. And all those tastes are giving us some sort of nutritional information about the food we're eating. Alright. Next, we have hearing. Hearing, we're going to use our ear and our cochlea. In our diagram here, we can see the outer ear, which works sort of like a funnel, into the actual sense organ, our cochlea. What we're measuring when we're using our hearing are pressure waves or vibrations in the air around us. And when we measure those pressure waves, we experience it as sound. But, again, it's just vibrations in the air. So I always think it's fun to think all those vibrations are actually hitting your entire body. The reason you don't feel them is that well, air doesn't exert a lot of pressure when it vibrates against your body. Your ear is just so fine-tuned and amplifies those pressure waves of those vibrations enough that you can experience them as sound. Our final sense that we're going to talk about is equilibrium. For equilibrium, we use our semicircular canals and our vestibule, and this is a structure that you can see here connected to the cochlear part of that inner ear. And with equilibrium, we measure movement and gravity. You can tell, even with your eyes closed, whether you're spinning, whether you're accelerating, whether you're upside down. Being able to do that is our sense of equilibrium. Okay. So those are the 5 organs and our 5 senses that we're going to talk about as our special senses. Again, going forward now, I want you to pay particular attention to the difference between the stimulus and how we perceive that stimulus. We'll practice that some more going forward, and I'll see you there.

Introduction to Special Senses Example 1

Alright. For this example, we're going to get kind of heady. It says, "For the following questions, carefully consider the relationship between perceptions and the different stimuli that cause them." So we were previously just talking about how there are stimuli in the world, things like pressure waves, chemical properties, or electromagnetic radiation, and then there are perceptions that we have, things like sound, things like smell or taste, things like colors or sight. Those two things are different. Right? These stimuli in the world only exist as our perception if someone is there to perceive it, if those things actually hit the receptor cells and they are perceived by the brain. So with that in mind, we're going to ask these questions. A, if a tree falls in the forest and no one is around, does it make a sound? Alright. You've probably been asked this before, but now you can give a physiological answer. My sort of real strict answer to this question would be, no. It makes pressure waves. Right? When that tree falls, certainly, the air around it, there's going to be vibrations, waves of pressure moving through it. But sound, the sound of the tree, only exists if it hits the receptors in somebody's ear and they perceive it as sound. Alright. Our next question. If the light is on in the basement and no one is home, what color are the walls? Right. So what would your answer be to that? Alright. My really strict physiological answer would be no color. There would be EM. There would be electromagnetic radiation, specific wavelengths of electromagnetic radiation that if someone were there, they might see color. But if no one is there, color doesn't exist. Color only exists when it hits the retina in someone's eye and someone's brain perceives it. Alright. Finally, if a hamburger is on the table and no one takes a bite, does it have a taste? Alright. What would you say to that? Alright. My real persnickety, very specific physiological answer would be no. It does not have a taste. It has chemical properties. When those chemicals dissolve in the saliva and hit your tongue. The gases hit your nose. You're going to smell that hamburger. You're going to taste that hamburger. But just in the hamburger, it doesn't have a taste. It has chemicals. Taste is a perception of those chemicals that are in the hamburger. Alright. Now, questions like these, you're unlikely to see on a test. But I really think understanding this distinction between the stimulus, the receptor that measures that stimulus, and how we experience that stimulus as a perception in our brain really helps you understand special senses a lot, lot better.

What is the difference between special senses and general senses?

• A. Special senses use action potentials, while general senses use graded potentials.
• B. Special senses are located in special sense organs, while general senses are distributed throughout the body.
• C. General senses include sight, taste, and equilibrium; special senses include pressure, temperature, and pain.
• D. The receptors for general senses are receptor cells, while special senses use modified nerve endings.

Which of the following correctly matches the sense to the type of stimulus it measures in the environment?

• A. Electromagnetic radiation: Smell.
• B. Pressure waves traveling through a fluid: Hearing.
• C. Chemical properties of gasses dissolved in a liquid: Equilibrium.
• D. Movement and gravity: Sight.

Here’s what students ask on this topic:

What are the five special senses and their corresponding organs?

The five special senses are vision, smell (olfaction), taste (gustation), hearing, and equilibrium. Each of these senses is linked to a specific organ. Vision relies on the eyes to detect electromagnetic radiation (light). Smell uses the olfactory epithelium in the nasal cavity to measure chemical properties in the air. Taste is facilitated by taste buds on the tongue, which detect five basic tastes: sweet, sour, salty, bitter, and umami. Hearing involves the cochlea in the ear, which detects pressure waves or vibrations in the air. Equilibrium is managed by the semicircular canals and the vestibule in the inner ear, which sense movement and gravity.

How does the eye perceive light and color?

The eye perceives light and color through its ability to detect electromagnetic radiation. Light enters the eye and is focused onto the retina, where photoreceptor cells (rods and cones) convert the light into electrical signals. Rods are responsible for detecting brightness, or the intensity of light, while cones are responsible for detecting color, which is determined by the wavelength of the light. The brain then processes these signals to create the perception of brightness and color. Brightness is the intensity of the radiation hitting the eyes, and color is a measure of the wavelength of light entering the eye.

What is the difference between the stimuli and perception in the special senses?

In the context of special senses, stimuli refer to the physical or chemical properties in the environment that are detected by sensory organs. Perception, on the other hand, is the brain's interpretation of these stimuli. For example, in vision, the stimulus is electromagnetic radiation (light), but the perception is the experience of brightness and color. In smell, the stimulus is chemical molecules in the air, while the perception is the experience of different odors. Understanding this distinction helps in comprehending how sensory organs detect stimuli and how the brain processes these signals to create sensory experiences.

How do the semicircular canals contribute to the sense of equilibrium?

The semicircular canals, located in the inner ear, play a crucial role in maintaining equilibrium by detecting rotational movements of the head. Each of the three canals is oriented in a different plane, allowing them to sense movement in any direction. Inside the canals, there is a fluid called endolymph and sensory hair cells. When the head moves, the fluid shifts, causing the hair cells to bend. This bending generates nerve impulses that are sent to the brain, which interprets the signals to determine the direction and speed of the movement. This information helps maintain balance and spatial orientation.

What are the five basic tastes detected by taste buds?

The five basic tastes detected by taste buds are sweet, sour, salty, bitter, and umami. Sweet taste is usually associated with sugars and indicates energy-rich foods. Sour taste detects acidity, which can signal spoiled or unripe food. Salty taste is primarily due to the presence of sodium ions and is essential for maintaining electrolyte balance. Bitter taste often serves as a warning for potentially toxic substances. Umami, a savory taste, is associated with amino acids like glutamate and is often found in protein-rich foods. These tastes provide important nutritional information about the food we consume.