General and Special Senses

The process of sensation is actually complex, yet we never really stop to think about what is actually happening in our bodies that make us realize we are smelling something good to eat or seeing the sun set.  The way our bodies perceive a smell, a touch, sight, hearing something, and even maintain equilibrium or balance.  Each of these sensations are called a sensory modality.  So what happens in our body as we perceive these sensations is starts when a given neuron carries information for only one sensory modality and its sensory receptor and responds vigorously to only one particular kind of stimulus.  This is a change in the environment that activates sensory receptors.  Some of these receptors are said to have selectivity, meaning that a given receptor may not respond at all or respond weakly.  The receptor selects one modality over all the others.  So what this all means is that nerve impulses from the eyes are perceived as sight, and those from the ears are perceived as sound.  The different types of sensory modalities can be grouped into two classes.  The two classes are general senses and special senses.  

The general senses include the somatic senses and the visceral senses.  The somatic sensory modalities include the tactile sensations, thermal sensations, pain sensations, and proprioceptive sensations.  The tactile sensations include touch, pressure, and vibration.  The thermal sensations include warm and cold.  The Proprioceptive sensations allow perception of both the static (nonmoving) positions of the limbs and body parts, and the movements of the limbs and head.  The visceral sensations provide information about the conditions within internal organs and are mediated by the autonomic nervous system.  The special senses include the sensory modalities of smell, taste, vision, hearing, and equilibrium or balance.

What we learned about how our body perceives physical stimuli is truly amazing.  Not everyones body reacts to the stimuli properly, for example, not everyones sight works properly.  Some people are near sighted, others far sighted.  They also may not be able to see color or only see a few certain colors.  Some people have accidents and some of their nerve receptors were severed and they can no longer feel anything in that area of their body.  It can be easily concluded that life just wouldn't be as fun if we weren't able to process the environment around us, or if our body failed us in certain areas of our sensory capabilities.