Explain the sense of touch



Sense of touch : Skin is the sensory organ for touch and is also the largest sense organ. Our sense of
touch allows us to feel light sensation like the touch of a feather as well as a heavy sensation like a stone falling on the toe. These sensations come from millions of microscopic simple sensory receptors , located all over the skin and associated with the general sensations of contact or pressure, heat, cold,
and pain. The receptors are located at different ^ levels within the skin and distributed unevenly.
Some parts of the body have a large number of these such as the finger tips, making them more sensitive.Structurally, these touch receptors are either free dendritic endings or encapsulated dendritic
endings present in the skin (and other parts of the body). When stimulated, these transmit the
sensation to the brain. Given below is a list of some of these receptors present in the skin.
(i) Free or bare dendritic nerve endings are present throughout the epidermis taking an extensive
branching or “zigzag” form. These respond chiefly to pain and temperature but some respond to pressure as well. The root hair plexuses, network of free nerve endings that surround hair follicles, are light touch receptors that detect bending of hairs.
(ii) Meissner’s corpuscles are small receptors in which a few spiraling dendrites are surrounded by specialized capsule (Schwann) cells. These are found just beneath the skin epidermis in dermal
papillae and are especially abundant in finger tips and soles of the feet. These are light pressure receptors that allow us to become aware of a caress or feel of our shirt against our skin.
(iii) Pacinian corpuscles are the large egg shaped
bodies .In each a single dendrite is surrounded by multilayers of capsule cells. These are scattered deep in the dermis and in the subcutaneous tissue of the skin .These are stimulated by deep pressure and respond only when pressure is first applied. Thus these receptors are best suited to monitor vibrations,on-off pressure stimulus the sense of touch allows us to detect different textures, temperatures, hardness and pain. Pain serves as a warning or alert system for the body. Whenever one or more of these sensory receptors are stimulated (by heat, cold, vibrations, pressure or pain) an impulse or action potential is generated. This impulse is then taken to the spinal cord and from there to the brain which analyses the stimulus and then generates appropriate response .The way brain interprets the sensation is our lives is also shaped by our personal experience in the past