By: Natasha Zelenka, Lexio Scott, Aneidi Andrew, and Michael Anderson

The sensory organs associated with the sense of touch:  The skin is the outer covering of the body consisting of three layers; it has a role in protection, tactile sensation and thermoregulation.  Meissners corpuscle are tactile receptor located especially at the level of the superficial dermis of the hands, feet, lips and genital organs; it is sensitive to light touching.  Free nerve endings are these receptors are common in epithelial tissues, where their free ends extend between epithelial cells. They are associated with the sensation of touch and pressure.  Pacinian corpuscles are large sensory bodies composed of connective tissue fibers and cells. They are common in the deeper subcutaneous tissues of the muscles, tendons, and joint ligaments. Pacinian corpuscles respond to heavy pressure and are associated with the sensation of deep pressure.

Sensory Receptors There are 5 specific sensory receptors of the skin: pain, heat, cold, touch, and pressure. 1. Pressure The sensation of touch is detected by mechanical forces that deform or displace tissues. Free nerve endings are receptors that detect a light touch to the skin and Pacinian corpuscles respond to heavy pressure.

Sensory Receptors 2. Pain 3. Temperature  Pain receptors function to protect the body because tissue damage stimulates them and signals a person to act in order to remove the unpleasant stimulation.  Warm receptors and cold receptors function by responding to the temperature changes on the nerve endings of the skin

4. Touch  Your sense of touch allows you to tell the difference between rough and smooth, soft and hard, and wet and dry.  It also functions to respond to touches on both the inside and the outside of your body.  Example: sensing a sore throat or a cold hand touching your arm.

SOMATIC PATHWAY  Sensation enters the sensory axons. Then goes to dorsal root ganglion.  The end of the axon enters the spinal cord, and the sensation goes up the cord to the brain (pink). The axons travels in the dorsal white matter of the spinal cord.  At the medulla, they merge together in the postcentral gyrus.  Then it will travel to the thalamus. Once in the thalamus, the third and final neuron (lavender) will go to cerebral cortex, the final target.

Somatic Disorders  Amorphognosia- Impaired ability to recognize the size and shape of objects by touch.  Ahylognsia- Inability to recognize differences in density, weight, and coarseness.