MAPPING

okay, maybe not that kind of mapping
I meant, who actually found what is under our SKIN
and how did they do it?

Under our skin there are many different receptors, things that can detect stimulus from the outside world; the types of receptors under our skin, scattered throughout the layers, are called mechanoreceptors, thermorceptors , and pain receptors.

MECHANORECEPTORS are stimulated by phyisical deformation caused by such stimuli as pressure, touch, stretch, motion and sound. The human sense of touch relies on these mechanoreceptors. They have been found to actually be modified dendrites of sensory neurons. There are four types of cells included in this category:

Pacinian Corpuscles- They are found in the deeper skin layers, therefore, they respond to strong pressure.
Meissner's Corpuscles- Found closer to the surface of the skin, used in dection of light touch.
Merkel's Disks- Also found closer to the surface of the skin and used for light touch.
Hair Cell- Used in the detection of motion. The cilia that project from the hair ell, bend and stretch, opening channels and creating chemical reactions.
- TOUCH- When these corpuscles are bent, or distorted, their membranes become depolarized, anaction potential occurs, opening channels, which allows for a signal of the touch to be sent to other places in the body.
- ADAPTATION- We would all go crazy if at any moment we could feel every stimulus that wa affectingour receptors, therefore it is a great advantage that our bodies can adapt to certain stimuli.
- MOVING STIMULI- Rarely in our lives do we encounter a situation where the stimuli and ourselves are not moving at all, usually we are in motion. It is much easier to identify something in your palm if you are allowed to roll it around and feel its dimensions. Therefore, the ability to use the somatosenses supplementary to the motor movements is also very beneficial.

THERMORECEPTORS respond to either heat or cold, they signal both surface and body core temperatures. Ther is some dispute as to the actual location of these receptors but two possibilities are:

Ruffini's end organs- posibly being the heat recptors.
end-bulbs of Krause- possibly being the cold receptors.
- EXPERIMENTS- although information is scarce, experiments have shown that the cold receptors are located closer to the surface of the skin, and the warmth receptors are then deeper.

PAIN RECEPTORS respond to exesses in heat, pressure, or chemicals released from inflammed tisses; there are different receptors for each. Pain receptors are: class of

nociceptors- naked dendrites. Most painful stimulus causes tissue damage.
- DAMAGED CELLS- once cells are damaged they rapidly produce a hormone called a prostaglandin. Once this hormone is freely available, it sensitizes the free nerve endings to another chemical. This process can be interrupted to relieve pain, insuch instances as aspirin. Aspirin affects the process by inhibiting the synthesis of prostaglandins.

So how was all of this accomplished? Well, one of the men that made a lot of progress in the area, was Von Frei researcher of the late 19th century. He would test his subjects for feelings of cold, hot, pain, pressure, etc. and he would make a map of all that he found. Then believe it or not, he would cut out that portion of the people's skin- ouch- and he would look at it in a microscope to saee the underlying mechanisms that read this type of sensory information. Of course his map ended up to be wrong, but his advancements made way for other research in the future.

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