The standard list of five senses doesn't really give our bodies credit for all the amazing things they are able to 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:
Depending on how you want to count it, there are between 14 and 20 different senses listed here.
- In your eyes you have two different types of light sensors. One set of sensors, called the rods, sense light intensity and work 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. Question 53 is interesting.
- 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:
These cells give us the sense of touch, sense of pain, sense of temperature and sense of itch. How Sun Tans and Sunburns work has some interesting information on the skin.
- heat sensitive
- cold sensitive
- pain sensitive
- itch sensitive
- pressure sensitive
- In the nose there are chemical sensors that give us our sense of smell. Question 139 is helpful.
- 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 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 in your large intestine sensors indicate when it is full.
- There is also the sense of hunger and thirst. How Food Works contains some information on hunger.
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 (also known as "eyes in the back of her head"). And many people feel they can sense when someone else is looking at them. No scientific proof for any of these senses yet...