The sensations of touch, pressure, pain, cold and heat are detected by the mammalian skin which is richly supplied with sensory receptors.
The sensory receptors in the skin are mainly primary sense cells. Some of the dendrites are finely branched with free ends while others are closed within capsules. The sensory receptors are not evenly distributed on the epidermis but are concentrated in the certain areas of the skin which makes such areas more sensitive to specific stimuli. For instance, the touch receptors are sensitive to small amounts of pressure and are located close to the surface of the skin, attached to hair follicles and concentrated in the finger tips, face and neck.
Pressure receptors (pacinian corpuscles) are sensitive to large amounts of pressure. Each receptor consists of the a single nerve ending surrounded by connective tissue and are found mainly in the dermis, joints and the muscles.
Thermo receptors are sensitive to cold and heat sensations and are widely distributed in the epidermis and dermis. They are free nerve endings some of which are enclosed in capsules.
They play an important role in the regulation of body temperature in warm blooded animals.
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