Touch Sensation
This week we started the chapter on touch sensation. We first covered concepts and terms having to do with touch receptors. There are five major kinds of touch receptors. Mechanoreceptors are the most common type of receptor and respond to physical distortion like bending. Nociceptors form the first part of the pain pathway. Thermoreceptors respond to changes in temperature and chemoreceptors fire in response to certain chemicals. Lastly, propioceptors help give us our sense of propioception, which tells us where our bodies are in space.
Propioception
In this week's Sacks reading (from The Man Who Mistook His Wife For a Hat) he relates the story of Christina, a "strapping young woman" of twenty-seven who lost her sense of propioception. She described the sensation as feeling "disembodied." Imagine the difficulties involved in not feeling in control of where your body was in space: trying to orient yourself, etc. What we are, essentially, is our minds, our thoughts. We depend on our bodies to communicate appropriately with us so that we may direct ourselves where we want to (physically) go. Sacks emphasizes the need for compassion towards individuals like Christina who have problems with the elusive sixth sense of proprioception.
More facts about touch.
How does a touch sensation, like a pat on the back, get to the brain? The first step is that touch is transduced in the touch receptors. Sound familiar? We've already learned about transduction in taste, olfaction, vision and audition; it's the process of translating physical stimuli into neural impulses that the brain can understand. So that's all about touch sensation for now. Next week we'll discuss pain mechanisms; see you then.