The standard list of five senses doesn't really give our bodies credit for all of the amazing things they can do. There are at least a dozen different things we can sense.
In order for us to have a sense, there needs to be a sensor. Each sensor is tuned to one specific sensation. For example, there are sensors in your eyes that can detect light. That is all that they can detect. To track down all of the different senses a person has, the easiest thing to do is to catalog all of the different sensors. Here is a reasonable list:
- In your eyes, you have two different types of light sensors. One set of sensors, called the rods, senses light intensity and works well in low-light situations. The other type, called cones, can sense colors (and actually, there are three different types of cones for the three primary colors) and require fairly intense light to be activated. See Why does it take my eyes several minutes to get used to darkness? for more information.
- In your inner ears, there are sound sensors.
- Also in your ears are sensors that let you detect your orientation in the gravitational field -- they give you your sense of balance.
- In your skin, there are at least five different types of nerve endings:
- heat sensitive
- cold sensitive
- pain sensitive
- itch sensitive
- pressure sensitive
- In your nose, there are chemical sensors that give you your sense of smell. Check out this Question of the Day.
- On the tongue, there are chemical receptors that give us our sense of taste.
- In your muscles and joints, there are sensors that tell you where the different parts of your body are and about the motion and tension of the muscles. These senses let us, for example, touch our index fingers together with our eyes shut.
- In your bladder, there are sensors that indicate when it is time to urinate. Similarly, your large intestine has sensors that indicate when it is full.
- There are also the senses of hunger and thirst.
The nervous system determines the countless sensations we feel all over our bodies every day. How does this work? What causes your leg to feel tingly when it falls asleep? How do you know when you're about to sneeze? This activity from Discovery Channel explains how sensations are produced in the body.
Depending on how you want to count it, there are between 14 and 20 different senses listed here.
There are some people who do seem to have other senses. For example, there are many people who can sense impending weather changes. My mother could always sense when I was about to make a mess (the sense also known as "eyes in the back of the head"). And many people feel that they can sense when someone else is looking at them. No scientific proof for any of these senses, yet...