SOMATIC SENSORY SYSTEM

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SOMATIC SENSORY SYSTEM

• D. C. MIKULECKY
• PROFESSOR OF PHYSIOLOGY
• AND
• FACULTY MENTORING PROGRAM

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FUNCTIONS OF THE SOMATIC SENSORY SYSTEM

• TACTILE RECEPTORS
• THERMAL RECEPTORS
• NOCIOCEPTORS
• PROPRIOCEPTORS

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TACTILE RECEPTORS

• SENSE MECHANICAL STIMULATION ON BODYS SURFACE
• TOUCH, PRESSURE, AND VIBRATION
• RAPIDLY ADAPTING (PACINIAN CORPUSCLE, HAIR
  RECEPTOR) OR SLOWLY ADAPTING (RUFFINI ENDING)

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TYPES OF SENSORY RECEPTORS IN THE SKIN
EPIDERMIS
DERMIS
RUFFINI ENDING
FREE NERVE ENDING
PACINIAN CORPUSCLE
HAIR RECEPTOR
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STATIC PROPRIOCEPTORS
LIMB POSITION II I
LIMB POSITION I
LIMB POSITION I I
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DYNAMIC PROPRIOCEPTORS
CHANGE IN LIMB POSITION
CHANGE IN LIMB POSITION
CHANGE IN LIMB POSITION
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THERMAL RECEPTORS

• SENSE CHANGES IN TEMPERATURE ON THE BODYS
  SURFACE
• COLD RECEPTORS BELOW 30 C
• WARM RECEPTORS ABOVE 30 C

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NOCIOCEPTORS

• PAIN RECEPTORS ACTIVATED BY HARMFUL STIMULI
• MECHANICAL
• HEAT

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PROPRIOCEPTORS

• REPORT POSITION AND MOVEMENTS
• STATIONARY OR STATIC (TONIC-JOINT CAPSULE AND
  CUTANEOUS MECHANORECEPTORS, MUSCLE SPINDLE
  RECEPTOR)
• DYNAMIC ACTIVATED BY LIMB MOVEMENTS

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ORGANIZATION OF SOMATIC SENSORY SYSTEM

• GENERAL PRINCIPLES
• ANATOMICAL CONSIDERATIONS

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GENERAL PRINCIPLES OF SOMATIC SENSORY ORGANIZATION

• LABELED LINE
• MOST PATHWAYS CROSS
• RELATIVE POSITIONS IN BODY ARE PRESERVED ALL THE
  WAY UP

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ANATOMICAL CONSIDERATIONS
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FURTHER ANATOMICAL CONSIDERATIONS

• CELL BODIES OF SOMATIC SENSORY NERVES ARE IN THE
  DORSAL ROOT GANGLION
• TWO MAJOR PATHWAYS DORSAL COLUMN AND
  ANTEROLATERAL

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ANATOMICAL CONSIDERATIONS TERMINOLOGY

• ROSTRAL-CAUDAL NOSE TO TAIL
• DORSO-VENTRAL BACK TO BELLY
• MEDIAL TOWARDS THE MIDLINE
• LATERAL TOWARDS THE SIDE
• ANTERIOR TOWARDS THE FRONT
• POSTERIOR TOWARDS THE BACK

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TERMINOLOGY ILLUSTRATED
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THE SPINAL CORD IN SOMATIC SENSORY FUNCTION

• WHITE AND GREY MATTER
• SEGMENTAL ORGANIZATION

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SEGMENTAL STRUCTURE OF SPINAL NERVES
DERMATOMES
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SPINAL CORD
DORSAL HORN
DORSAL
GREY MATTER
DORSAL ROOT GANGLION
LATERAL
VENTRAL HORN
WHITE MATTER
SPINAL NERVE
VENTRAL
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TOUCH AND PRESSURE
DORSAL COLUMN PATHWAY
INCOMONG SENSORY NERVE TRAVELS UPWARD IN THE
DORSAL COLUMN AND SYNAPSES IN THE DORSAL COLUMN
NUCLEUS
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PAIN AND TEMPERATURE
ANTEROLATERAL PATHWAY
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LESION ON RIGHT HALF OF SPINAL CORD

• LOSS OF PAIN SENSATION ON LEFT SIDE BELOW LESION
• LOSS OF TOUCH AND VIBRATION ON RIGHT SIDE BELOW
  LESION
• LOSS OF BOTH ON RIGHT SIDE AT SAME LEVEL
• NO LOSS ABOVE LESION

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THE CRANIAL NERVES

• TRIGEMINAL
• GLOSSOPHARYNGEAL
• PLAY SAME ROLE AS SPINAL NERVES

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THE THALAMUS IN SOMATIC SENSATION

• MAJOR SITE FOR RECEIVING SENSORY INFORMATION
• VENTRAL POSTERIOR LATERAL NUCLEUS (VPL)
• SENDS SENSORY INFORMATION TO THE CORTEX

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THE THALAMUS IN SOMATIC SENSATION
SENSORY NEOCORTEX
MEDIAL LEMNISCUS
DORSAL COLUMN NUCLEI
MEDULLA
DORSAL COLUMN
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SOMATOSENSORY CORTEX

• NEOCORTEX REGION OF CORTEX WHICH EVOLVED MOST
  RECENTLY
• PRIMARY POST CENTRAL GYRUS
• SOMATOTOPIC ORGANIZATION

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THE SOMATOSENSORY CORTEX
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SOMATOTOPIC ORGANIZATION OF THE SENSORY CORTEX
GENETALS TOES FOOT LEG HIP . . . LIPS TONGUE
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SOMATOTOPIC ORGANIZATION OF THE SENSORY CORTEX