1. مسیرهای انتقال حسهای پیکری
جلسه ششم
مسیرهای انتقال حسهای پیکری

7. Primary Afferent Nerves
Receive information from receptors
Project to CNS
Parallel pathways
touch & proprioception & …(DCML)
pain & temperature & …(Anterolateral System)

9. Somatosensory Pathways
Touch & Proprioception
Dorsal Column-Medial Lemniscal pathway (DCML)
Pain and Temperature -
Anterolateral (Spinothalamic) system
Trigeminal pathway
face & neck
cranial nerve V, also others ~ 9

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

11. Somatosensory System(1)
Dorsal Column – Medial Lemniscus
Thalamocortical Pathways

12. 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

13. Schematic representation of the main mechanosensory pathways (Part 1)
neuro4e-fig r.jpg

14. 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

15. Discriminative Touch Cerebral Cortex 3 Thalmus 2 1 Brainstem
multipolar
Cerebral Cortex 3
Thalmus 2 1
Brainstem
Unipolar nerve

16. Touch S1 R R Spinal Cord Dorsal Column-Medial Lemniscal pathway
Thalamus - VP
Medial lemniscus
Medulla
Dorsal Column R
DRG R
Spinal Cord

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

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

19. Dorsal Column- Medial Lemniscal System
In the PNS/Spine
Pacinian corpuscle
Cervical
Thoracic
Lumbar
Sacral
Fasciculus
cuneatus
Fasciculus
gracilis
Meissner’s corpuscle

20. Dorsal Column-Medial Lemniscal System
Pons and Medulla
Nucleus gracilis (lower body)
Nucleus cuneatus (upper body)
Medulla
Decussation

21. Dorsal Column- Medial Lemniscal System
Midbrain-Cortex
Homunculus
Thalamus
Midbrain
Medial lemniscus

22. Dorsal Column Pathways & Medial Lemniscus
Discriminative Touch
Pressure
Vibratory Sensation
Fine Discrimination
Two-Point Tactile Test
Proprioception (conscious)
Sense of movement & position (eg: is your toe up or down?); Muscle Spindles, GTOs & Joint Receptors

26. Nucleus Cuneatus
Nucleus Gracilis

27. Dorsal Column Pathways/ Fasciculus Cuneatus
Input from the upper extremity, down to the level of T5 passes into the Fasciculus Cuneatus.
Somatotopic Organization: Input from the arm (Fasciculus Cuneatus) is lateral to input from the leg (Fasciculus Gracilis)

28. Dorsal Column Pathways/ Fasciculus Gracilis
Input from the lower extremity, up to the level of T6 passes into the Fasciculus Gracilis of the dorsal funiculus.
The first order neuron enters the cord & ascends without either synapsing or crossing to the opposite side.

30. Dorsal Column Pathways & Medial Lemniscus
Cerebral Cortex
VPL Thalamus (Synapses again here)
Nucleus Cuneatus & Gracilis
Fasciculus Cuneatus
Fasciculus Gracilis
Dorsal Root Ganglia
Synapses
and Crosses –
now as the
Medial
Lemniscus

33. VPL & VPM

35. Schematic representation of the main mechanosensory pathways (Part 2)
neuro4e-fig r.jpg

36. Pain and Temperature Anterolateral System Cerebral Cortex 3 Thalmus 21
Brainstem/spinal cord

37. The Anterolateral System
Substantia
Gelatinosa

39. Spinal Cord
dorsal columns
Dorsal
Ventral
lateral columns

40. Schematic representation of the main mechanosensory pathways
neuro4e-fig jpg

48. To Cerebellum(1) 1-Direct Pathways
A) Posterior(dorsal) Spinocerebellar Tract
B) Cuneocerebellar Tract
C) Anterior(ventral) Spinocerebellar Tract
D) Rostrospinocerebellar Tract

49. To Cerebellum(2) 2- Indirect Pathways A) Spinocervicocerebellar Tract
B) Spinoolivocerebellar Tract

50. 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

51. Dorsal Spinocerebellar Tract
1. ORIGIN: Clarke’s nucleus in the thoracic spinal cord
2. COURSE: lateral columns of the spinal cord. Inferior cerebellar peduncle.
3. LATERALITY: Uncrossed
4. TOPOGRAPHICAL ORGANIZATION: Lower limbs only.
5. DESTINATION: Cerebellar cortex and deep nucleus (not shown). Terminations are mossy fibers.
6. FUNCTION: Information about muscle stretch and contraction.
7. DYSFUNCTION: Possible ataxia from loss of input to cerebellum.

52. Dorsal spinocerebellar tract travels in lateral column to the cerebellum

53. Dorsal spinocerebellar tract travels in lateral column to the cerebellum

54. 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

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

57. Thalamocortical Pathway
Origin - VPL
Course – Posterior limb of internal capsule
Laterality - Uncrossed
Topographical Organization - yes
Destination – Primary somatosensory cortex, areas 1, 2, 3
Function – DC- ML functions
Dysfunction – Loss of somatic sensations

59. The Brown- Sequard Syndrome
CHARACTERISTIC PATTERN OF SENSORY LOSS DUE TO LOCALIZED DAMAGE ON ONE SIDE OF SPINE
USUALLY ACCOMPANIED BY MOTOR LOSS AS WELL

60. 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
LOSS OF MOTOR ON RIGHT SIDE BELOW LESION

62. Brown-Sequard syndrome