The Cutaneous Senses

Somatosensory System

• The cutaneous senses

  • Perception of touch and pain

• Proprioception

  • Perception of the position and movement of the body and limbs

  • More cognitive (awareness)

• Kinesthesis

  • Perception of the position and movement of the body and limbs

  • More behavioral - muscle memory/hand-eye coordination

• Vestibular sense

  • Position and movement of the head

  • Not part of the somatosensory system

Cutaneous senses

• Epidermis - top protective layer

• Dermis - contains receptors

• Hypodermis - fatty underlayer

Mechanoreceptors

• These 4 receptors responds to distortion of the skin

• Nearer surface

  • Meissner’s corpuscle

  • Merkel’s Disk

• Deeper under surface

  • Ruffini’s endings

  • Pacinian Corpuscle

Merkel Receptors

• Fires to continuous pressure, slow adapting

• detect low frequency vibrations (5-15Hz)

• Small receptive fields

• found in glabrous or hairy skin, fingertips and lips

• Perception of fine details, gentle touch, tactile discrimination

Meissner’s Corpuscle

• Fires to on/off stimuli, rapidly adapting, low vibrations (10-15Hz)

• Small receptive fields

• Found on thick glabrous skin like fingertips and lips

• Important for light touch and tactile discrimination, handgrip

Ruffini’s Endings

• Fires continuous pressure, slow adapting

• In both glabrous and hairy skin

• Large receptive field

• Perception of stretching of the skin, important for gripping objects

• Contribute to proprioception and kinesthesia

• Also detect warmth

Pacinian Corpuscles

• Fires to on/off stimuli, rapidly adapting

• Large receptive field

• Located in viscera, joints, breasts, genitalia

• Sense deep transient pressure and high frequency vibrations

Pathways to the Brain

• Medial Lemniscal

  • Large fibers

  • Sense the position of the limbs (proprioception)

  • Sense touch

• Spinothalamic

  • Small fibers

  • Sense temperature and pain

Neural Plasticity

• Special training can affect the brain

• Humunculus