The Somatic Senses

The somatic (general) senses collect information about cutaneous sensations (tactile sensations on the surface of the skin) and proprioceptive sensations. The following stimuli are detected:

• Tactile stimuli are detected by mechanoreceptors and produce sensations of touch and pressure:

  • Merkel discs are receptors with free nerve endings that detect surface pressure (light touch). They are located at the bottom of the epidermis.

  • Root hair plexuses are receptors with free nerve endings that surround hair follicles and detect hair movement.

  • Corpuscles of touch (Meissner's corpuscles) are receptors with encapsulated nerve endings located in the dermal paillae (near the surface) of the skin that detect surface pressure (light touch).

  • Pacinian corpuscles are encapsulated nerve receptors that detect deep pressure and are located in the subcutaneous layer (below the skin).

• Thermal stimuli are detected by free nerve ending thermoreceptors sensitive to heat or cold.

• Pain stimuli are detected by free nerve ending nociceptors.

• Proprioceptive stimuli are detected by the following receptors:

  • Muscle spindles are mechanoreceptors located in skeletal muscles. They consist of specialized skeletal muscle fibers enclosed in a spindle-shaped capsule made of connective tissue.

  • Golgi tendon organs are mechanoreceptors located at junctions of tendons and muscles.

  • Joint kinesthetic receptors are mechanoreceptors located in synovial joints.

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