1. Sensory system

2. Sensory system
The sensory system is composed of subsystems, each transmitting specific information to the central nervous system

3. Somatosensory system
The somatosensory system is the body sensation. It monitors a wide variety of stimuli from all over the body from the activity in receptors found in the skin, and proprioceptors in the muscle and the joints

4. The functions of the Somatosensory system
- to monitor the contract of objects and surface with the skin, particularly the hands and feet
- to report the position of body segments in space and in relation to each other(body scheme)
- to initiate sensory activity for the interpretation of harmful stimuli

5. The Somatic Sensory Cortex
- Primary somatosensory cortex(SⅠ)
      : Brodmann's areas 1,2,3a and 3b
- Seconcary somatosensory cortex(SⅡ)

6. >20 types of receptors in skin: touch, temperature, stretch, etc
2 pathways to brain
Dorsal columns
Precise touch, joint angle, etc.
Crosses side at medulla
Antero-lateral Tract
Coarse information regarding pain and temperature
Convergence of information
Crosses side at entry in spinal column

7. Hierarchy of Sensory Fibers
Specialized Receptors
Single Nerve Fiber
Sensory Fiber Bundle
Spinal Nerve
Dorsal Root Ganglia
Dorsal Column Nuclei
Spinal Motorneurons or Reticular Formation
Thalamus
Primary and Association Cortex (Parietal Lobe)

8. Organization
Each tract mediates specific modalities of sensation, somatotopic organization in tracts and cortex
Mechanoreceptive
Mechanical displacement of nerve endings
Touch (fine and diffuse), pressure, vibration, kinesthesia
Thermoreceptive
Cold and Heat
Nociceptive
Pain

9. Specialized Receptors
Receptors specialize by type of stimulus
Adaptiveness: Reduction of response to sustained stimuli
Basic Types of Sensory Receptors
Encapsulated Endings
Adapting (tactile)
Pacinian corpuscle: deep pressure touch and high frequency vibration.
Meissner’s corpuscle: light touch, such as the fingertips, palms, soles, lips, tongue, face
Free Nerve Endings (pain, temp, some tactile)
Nonadapting
Expanded Tip Endings (tactile, temp)
Moderately adapting

10. 1) Classified according to their diameters
◆ Primary Afferent Axons (Fibers)
1) Classified according to their diameters
2) The greater their diameter, the greater their conduction velocities
3) Peripheral nerve fibers show differences in the following functional properties

11. Three neuron Organization
1st Order
Dorsal Root Ganglion
2nd Order
Enter CNS at spinal cord or brainstem
Project to opposite side crossing midline to thalamus
3rd Order
Thalamus neurons which project to cortex

12. Anatomical Divisions
Dorsal Column-Medial Lemniscal (or Epicritic System)
Fine discriminative touch, vibration, limb position, kinesthesia & deep pressure
Position sense
Proprioception - Awareness of limb position
Kinesthesia - Awareness of limb movement
Anterolateral (or Protopathic System)
Pain, temperature and diffuse touch
Lateral spinothalamic tract
Anterior spinothalamic tract

13. Dorsal Column-Medial Lemniscal System
Important for skilled movements
Stereognosis - Fine touch discrimination
Graphesthesia - Recognizing numbers written on body
Two and multiple point touch
Deep touch
Receptors
Meissner’s and Pacinian Corpuscles
Encapsulated end receptors
Highly sensitive and adaptable
Muscle Spindle Organs
Kinesthesia
Proprioception

14. Neural Pathways Neural Pathways Fasciculus Gracilis
Fasciculus Cuneatus
Path
Spinal Ganglion (1)
Gracilis or Cuneatus Nucleus (2)
Through Medial Lemniscus to Thalamus (3)
Thalamus to Cortex
Mediate discriminative
Touch from different
Body areas; follow
three-neuron
organization

15. Levels of Reception Fasciculus Gracilis Fasciculus Cuneatus
Sacral to Midthoracic Level
Lower Body
Fasciculus Cuneatus
Above Midthoracic Level
Upper Body

16. Pathway Spinal Cord Brainstem Nuclei
Thalamus (N. Ventral Posterolateralis)
Thalamus through Internal Capsule to Primary Sensory Parietal Cortex
Primary to Association Cortex
Mapped spatially (homunculus)

17. Medial Lemniscal Pathway: Mechanoreceptors & Proprioception

18. The homunculus

19. Anterolateral system Pain, Temperature, & Diffuse Touch
Three-tier neuron organization system
Enter at spinal ganglion (1st)
Cross in spinal tract (2nd order)
Ventral posterolateral n. of thalamus (3rd)
Two Tracts
Lateral Spinothalamic
Anterospinothalamic

20. Pain and Temperature Cerebral Cortex 3 Thalmus 2 1
Anterolateral System
Cerebral Cortex 3
Thalmus 2 1
Brainstem/spinal cord

21. Spino-Thalamic Pathway: Temperature & Pain

22. Lateral Spinothalamic Tract
Receptors - Free Nerve Endings
Neural Pathway
Nocioceptors (pain)
Dorsolateral spinal cord (up or down several segments)
spinal cord entrance
Substantial Gelatinosa and Proprius
Where 1st order neurons connect with 2nd order neurons
Lateral Spinothalamic Tract
Cross Midline (2nd order)
Spinal Lemniscus (brainstem)
Thalamus (VPL) to Cortex
Collaterals to Subcortical structures

23. Anterospinothalamic Tract
Discrimination of Diffuse touch
Receptors: All three types
Encapsulated endings
Free nerve endings
Expanded tip endings
Neural Pathway
Skin to ganglia (1st)
Dorsolateral spinal cord (up and down seg)
Proprius and Substantia Gelatinosa (2nd)
Go to spinothalamic tract to VPL (thalamus) to postcentral gyrus
Collaterals to subcortical structures
Clinically, interruption causes no obvious deficit

24. Unconscious Proprioception
Conscious proprioception by dorsal column-medial lemniscal system
Unconscious involved in walking, articulating, writing, swallowing, and eye movement.
Two order neural system
Tracts
Dorsal Spinocerebellar
Cuneocerebellar
Ventral Spinocerebellar
Receptors
Muscle spindles and Golgi tendon organs located in muscles and limb joints

25. Ventral Spinocerebellar Tract
Mediates unconscious proprioception
Lower limbs to bilateral cerebellum
Sacral and Lumbar levels through ventrolateral Spinocerebellar tract to opposite cerebellar hemisphere

26. Dorsal Spinocerebellar Tract
Mediates unconscious proprioception
Lower limbs and middle regions of body to to bilateral cerebellum
Spinal ganglion to nucleus dorsalis of Clark at third lumbar segment
Do not cross and enter ipsilateral cerebellar hemisphere

27. Cuneocerebellar Tract
Mediates upper limbs and neck
Uncrossed fibers to ipsilateral external cuneate nucleus to cerebellum
Clinical Considerations
Romberg used to determine some function
Difficult to test clinically

28. Sensory abnormalities
Cerebral cortex region
- conscious proprioception
- two-point discrimination
- stereognosis
- touch & pain
Cerebellum region
- ataxia

29. Prerequisites of Treatment
Normalising muscle tone
Suitable working positions
Stimulationg sensating without
increasing spasticity
Cooperation of patient
Allowing sufficient time
Consideration of other disabilities
Repetition of stimuli
Variation of stimuli
Adjustment of training intensity

30. Haptics