We have the classical 5 but there are a lot more. Time Gravity Location of body CO2 in blood Pain Heat Cold I can't remember anymore but some scientists list over 20.
I would argue that several of those listed [gravity, pain, cold (which is just lack of heat/energy], heat, possibly location of body) are all manifestations of the same sense, touch. I like the standard five. Touch, taste, hearing, sight, smell. Id consider adding time/ self awareness (maybe odd that I'd lump them together, but it makes sense to me) and combining taste and smell.
They use different receptors and things like that. And if pain is touch why doesn't more things cause us pain?
By that metric, all senses are just derived from touch, essentially. Olfaction is simply small molecules locking onto receptors and sending signals to the brain. Sight is photons touching receptors and sending signals to the brain. All senses are then merely the contact of something on a receptor, which is essentially just what touch is. Also, the vestibular sense (roughly, gravity) is located entirely within the ear, so it'd be more related to hearing than to touch. Although, again, hearing is basically just modified touch itself.
I'm not sure I buy that one. In what way do people sense time other than by way of observations of the world around them, and their sense of their own bodily functions? You might say that people have an internal clock of sorts, but that seems to be based upon observations of a person's surroundings. It's a secondary sense based on our ability to perceive orientation and detect pressure. We don't really sense gravity--we sense the side effects of gravity. Obviously incorrect, as demonstrated by the blindfolded hiker experiment. We have a sense of orientation on two axis, not three. IIRC, the mechanism is actually related to CO2 in the lungs, not in the blood itself. The two are linked, so the end result is basically the same. Generally considered a part of the sense of touch. I'll grant that we have a sense of orientation that generally isn't considered among the senses. It's more accurate, I think, to say that humans have five primary senses and many other secondary senses based upon unconscious analysis of those five senses.
Depending on how you define a sense somewhere between 12 and 25. The myth that we have five senses comes from Socrates who listed the five most obvious senses, we have many more. How do we feel hungry? We don't touch it or see it or hear it or smell it or taste it. How can you touch the end of your nose when you have your eyes closed, how do you know where your finger is?
People have a sense of time. Your body regulates itself on this fact. It's automatic, it's not from conscious observation. It seems to regulate itself from sunlight. People who are put into rooms with no clocks and no sun run on a 25 hour day. They will wake up, go to bed, eat, etc on a 25 hour day. That's time. It's not a fluke.
Close your eyes. Touch your nose. How did you do that? Because you have a sense that tells you where your body parts are. And if something is generally considered you're probably talking about the layperson and then it's generally wrong.
Not really a primary sense; the body can model that in the brain. Tell a child to do the same and they'll fail. That's how the textbooks represent it.
Gravity, motion, orientation, that's sensed by the tiny hairs embedded in a fluid in the inner ear. Time such as the sleep-wake cycles, night and day, that's sensed by the pineal gland derived from the third/middle eye of our primitive (armoured/jawless) fish ancestors. Touch is one of the 5 primary senses and is somatic, while pain can be somatic or visceral. Systems that ensure homeostasis such as the bloodstream CO2 sensitivity uses chemical receptors rather than nerve endings, so I don't know if you can call it a sensory system.
Um, yea, we have many ignorant people with more education that common sense. Time? Time is a misconception by our lack of perception. Location of Body? This is not a sense, it is cognitive ability and reasoning. CO2 in blood? Not sure what you mean. Gravity, Pain, heat & Cold are all manifestations of touch.
You can list differences and similarities between our various sensory receptors and categorize them in a way that pleases you, but it's all rather arbitrary. Personally, I feel it's much more interesting to get a rough understanding of what's going on when our senses actually sense something. For example, Muscle spindels are used to find out how stretched our muscles are. That's probably part of what was called "Location of Body" before. They use some of the fastest neurons to transmit that information, because knowing the length changes of our muscles is essential for precise control over our bodies. In some cases, that information doesn't even make it to the brain for a faster response (reflexes). Here's a nice engineering analogue to muscles and their spindels using a cart and rotary encoders. [ame="http://www.youtube.com/watch?v=cyN-CRNrb3E&feature=related"]Triple Pendulum on a Cart - YouTube[/ame] I wonder whether a human could balance a triple pendulum with enough training. Any guesses?
