The Sensory System: Definition, Parts & Functions

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  • 0:01 Definition
  • 1:35 Receptors
  • 3:47 Signals
  • 5:52 Lesson Summary
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Lesson Transcript
Instructor: Devin Kowalczyk

Devin has taught psychology and has a master's degree in clinical forensic psychology. He is working on his PhD.

This lesson will examine how the sensory systems are integrated and how they function as a whole. Instead of telling you ears hear and eyes see, we will examine how these systems are actually very similar in terms of reception, signals, and translations.


You can hear me right now. That is because the speakers are creating vibrations and the density fluctuations in the air. These vibrations traveled to your ear and moved a mechanical system that your brain could read. Signals then traveled to your brain where they were decoded.

If that isn't amazing enough, you can see this. Your screen produces groups of photons that fly through the air at the speed of light. They strike specialized cells in your eyes that are so sensitive they can feel light. They then send a signal to your brain, all the way to the back of it, where it is decoded and figured out. That's pretty flipping amazing.

The sensory system is a group of subsystems used for detecting and understanding the world around you. We just discussed the auditory and the visual system in brief, but there is also smell, taste, balance, proprioception (or the position of your body), and at least half a dozen types of touch sensations.

I was doing some thinking as I wrote this, and I realized you've already been handed the sensory systems as discrete units - the eyes do this; the ears do that. You've most likely had that kind of information before. What you haven't had is a holistic view of how these systems are similar. Let's look at the systems as a whole and maybe shake up some stuff.


What makes the sensory system unique is its ability to sense things, which sounds kind of stupid and 'no duh' because you haven't ever realized how limited your sensory organs are. Let's say I have a chopstick, one chopstick, and some local anesthetic. I spray the anesthetic on your scalp and proceed to cut a hole in your head, exposing your brain. I then take my chopstick and push it into your brain. My question is, 'What do you feel?'

The answer is, 'Nothing.' Your brain doesn't feel pain, pressure, or touch. Your brain, the great and powerful human brain, lacks receptors, which are specialized neurons designed to obtain a particular type of information that is then sent to a particular part of the brain. Your brain, which interprets pain, does not actually feel pain. There are no pain receptors in your brain.

If you find this a bit maddening and hard to believe, you aren't alone. Many people I have met in graduate school find this impossible. Receptors have been divided up into five different types. Let's look at each one and which sensory system they can be found in:

  • Chemoreceptors detect ionic and molecular changes or presence. Think smell and taste.
  • Mechanoreceptors detect changes and fluctuations in pressure, position, and movement. Think hearing, touch, balance, and stretching.
  • Electromagnetic receptors detect light, radiation, and magnetic fields. Humans only have visible light detection in their eyes, but sharks have specialized organs for detecting bodily electricity.
  • Thermoreceptors detect hot and cold temperatures. Obviously, this is a temperature detection, both of the outside world and inside the body, since you need to keep a constant temperature.
  • Pain receptors detect pressure, chemicals, and severe heat. These are found all over your skin and tell you if something is wrong.


When a receptor is triggered, it sends a signal. How the receptor is triggered, though, depends on what type it is. Let's look at a fairly common way and then in a more unusual way.

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