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SOMATIC SENSORY SYSTEM
D. C. MIKULECKY
PROFESSOR OF PHYSIOLOGY
AND
FACULTY MENTORING PROGRAM
FUNCTIONS OF THE SOMATIC
SENSORY SYSTEM
TACTILE RECEPTORS
THERMAL RECEPTORS
NOCIOCEPTORS
PROPRIOCEPTORS
TACTILE RECEPTORS
SENSE MECHANICAL STIMULATION ON
BODY’S SURFACE
TOUCH, PRESSURE, AND VIBRATION
RAPIDLY ADAPTING (PACINIAN
CORPUSCLE, HAIR RECEPTOR) OR
SLOWLY ADAPTING (RUFFINI ENDING)
TYPES OF SENSORY
RECEPTORS IN THE SKIN
EPIDERMIS
DERMIS
RUFFINI
ENDING
FREE
NERVE
ENDING
HAIR
RECEPTOR
PACINIAN
CORPUSCLE
STATIC PROPRIOCEPTORS
LIMB
POSITION I
LIMB
POSITION I I
LIMB
POSITION II I
DYNAMIC
PROPRIOCEPTORS
CHANGE
IN LIMB
POSITION
CHANGE
IN LIMB
POSITION
CHANGE
IN LIMB
POSITION
THERMAL RECEPTORS
SENSE CHANGES IN TEMPERATURE ON
THE BODY’S SURFACE
COLD RECEPTORS: BELOW 30° C
WARM RECEPTORS: ABOVE 30° C
NOCIOCEPTORS
PAIN RECEPTORS ACTIVATED BY
HARMFUL STIMULI
MECHANICAL
HEAT
PROPRIOCEPTORS
REPORT POSITION AND MOVEMENTS
STATIONARY OR STATIC (TONIC-JOINT
CAPSULE AND CUTANEOUS
MECHANORECEPTORS, MUSCLE SPINDLE
RECEPTOR)
DYNAMIC: ACTIVATED BY LIMB
MOVEMENTS
ORGANIZATION OF SOMATIC
SENSORY SYSTEM
GENERAL PRINCIPLES
ANATOMICAL CONSIDERATIONS
GENERAL PRINCIPLES OF SOMATIC
SENSORY ORGANIZATION
LABELED LINE
MOST PATHWAYS CROSS
RELATIVE POSITIONS IN BODY ARE
PRESERVED ALL THE WAY UP
ANATOMICAL CONSIDERATIONS
TYPE
DIAMETER (m)
CONDUCTION
VELOCITY (m/s)
Ia(A)
22
120
PRIMARY MUSCLE
SPINDLE
Ib(A)
22
120
PRIMARY TOUCH
AND PRESSURE
II(A)
13
70
III(A)
5
15
SECONDARY MUSCLE
SPINDLE, TOUCH, AND
PRESSURE
LIGHTLY MYELINATED:
TOUCH, PRESSURE, AND PAIN
IV(C)
1
2
SENSORY
INFORMATION
UNMYELINATED:
PAIN AND TEMPERATURE
FURTHER ANATOMICAL
CONSIDERATIONS
CELL BODIES OF SOMATIC SENSORY
NERVES ARE IN THE DORSAL ROOT
GANGLION
TWO MAJOR PATHWAYS: DORSAL
COLUMN AND ANTEROLATERAL
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
TERMINOLOGY ILLUSTRATED
ROSTRAL
(SUPERIOR)
DORSAL
VENTRAL
CAUDAL (INFERIOR)
THE SPINAL CORD IN SOMATIC
SENSORY FUNCTION
WHITE AND GREY MATTER
SEGMENTAL ORGANIZATION
SEGMENTAL STRUCTURE
OF SPINAL NERVES
DERMATOMES
SPINAL CORD
DORSAL
HORN
DORSAL
DORSAL
ROOT
GANGLION
SPINAL
NERVE
GREY
MATTER
LATERAL
WHITE
MATTER
VENTRAL
HORN
VENTRAL
TOUCH AND PRESSURE
DORSAL
COLUMN
PATHWAY
INCOMONG SENSORY NERVE TRAVELS UPWARD IN
THE DORSAL COLUMN AND SYNAPSES IN THE
DORSAL COLUMN NUCLEUS
PAIN AND TEMPERATURE
ANTEROLATERAL
PATHWAY
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
THE CRANIAL NERVES
TRIGEMINAL
GLOSSOPHARYNGEAL
PLAY SAME ROLE AS SPINAL NERVES
THE THALAMUS IN
SOMATIC SENSATION
MAJOR SITE FOR RECEIVING SENSORY
INFORMATION
VENTRAL POSTERIOR LATERAL NUCLEUS
(VPL)
SENDS SENSORY INFORMATION TO THE
CORTEX
THE THALAMUS IN
SOMATIC SENSATION
SENSORY
NEOCORTEX
MEDIAL
LEMNISCUS
DORSAL COLUMN
NUCLEI
DORSAL COLUMN
MEDULLA
SOMATOSENSORY CORTEX
NEOCORTEX: REGION OF CORTEX
WHICH EVOLVED MOST RECENTLY
PRIMARY: POST CENTRAL GYRUS
SOMATOTOPIC ORGANIZATION
THE SOMATOSENSORY
CORTEX
SOMATOTOPIC ORGANIZATION
OF THE SENSORY CORTEX
GENETALS
TOES
FOOT
LEG
HIP
.
.
.
LIPS
TONGUE
SOMATOTOPIC ORGANIZATION
OF THE SENSORY CORTEX