The greatest “general knowledge” of this century – that you have 5 senses, is wrong. What? Yes, that’s right – wrong. You actually have 8 senses. 8, completely different, very necessary senses. If you think I’m crazy, I’ll post sources at the end of this article. I promise you, if you hear me out, you may get it. First you may be wondering: Okay, fine, there’s 8 senses, but why haven’t I heard of them? Well, the trouble with the other 3 senses is that they only come up when there’s a problem. Most people day to day have no (or little) trouble with these senses.
The 8 senses start off simply. We have the 5 you all know (and hopefully, if you’re lucky, love). I won’t tell you what these do – chances are, you already know…
Now, the difficulty comes in when we get to the last 3.
The vestibular system contributes to balance and orientation in space. It is the leading system informing us about movement and position of head relative to gravity. Our movements include two positions rotations and linear directionality. Thus, the vestibular system has two related components: the semicircular canal system, (related to detecting rotation) and the otoliths, (related to detecting linear acceleration/deceleration). The vestibular system sends signals primarily to the neural parts of the brain that control our eye movements, and that keep us upright. (SPD Star)
The proprioceptive system (sometimes abbreviated as “prop” by therapists when they talk about it) senses the position, location, orientation, and movement of the body muscles and joints. Proprioception provides us with the sense of the relative position of neighboring parts of the body and effort used to move body parts. Proprioception is activated by input to a proprioceptor in the periphery of the body. The proprioceptive sense combines sensory information from neurons in the inner ear (detecting motion and orientation) and stretch receptors in the muscles and the joint-supporting ligaments for stance. (SPD Star)
The eighth, often neglected, but frequently problematic sensory system in SPD is the Interoceptive System. Interoception refers to sensations related to the physiological / physical condition of the body. Interoceptors are internal sensors that provide a sense of what our internal organs are feeling. Hunger and thirst are examples of interoception. Interoception detects responses that guide regulation, including hunger, heart rate, respiration and elimination. The Interoceptive stimulation is detected through nerve endings lining the respiratory and digestive mucous membranes. Interoception works the vestibular and proprioceptive senses to determine how an individual perceives their own body. Well-modulated interoception helps the individual detect proprioceptive and vestibular sensation normally. For example, if a person feels his/her heart pounding, while it is not comfortable, trauma from the stimulation is not likely; nor will the stimulation be craved. The same is true for hunger and thirst, as well as the feeling of the need to urinate or have a bowel movement.
A more detailed, in-depth, account of these systems can be found on the SPDStar website.