Tracts and Tract Lesions

Question 1

Dorsal Column (Medial Lemniscus) Pathway

Answer 1

• Touch, pressure, proprioception, 2 pt. discrimination, vibration - DRG to Nucleus Cuneatus (UL) or Gracilus (LL) via fasciculus cuneatusor fasciculus gracilus -> medial lemniscus to VPL -> VPL to primarysomatosensory cortex - Crosses in caudal medulla as internal arcuate fibers

Question 2

Spinothalamic Pathway

Answer 2

• Pain and temperature - DRG to substantia gelatinosa via Lissauer’s tract -> cross in white anteriorcommissure -> spinothalamic pathway to VPL -> VPL to Somatosensorycortex

Question 3

Trigeminal (touch, pressure, proprioception)

Answer 3

• DRG -> Trigeminal ganglion -> primary/main/principal nucleus oftrigeminal -> cross in pons -> ascend via trigeminothalamic tract to VPM -> VPM to primary somatosensory cortex

Question 4

Lateral Corticospinal Tract

Answer 4

UMN (1st orderneuron) = in Motor Cortex - Axons travel via the Internal Capsulethrough the Cerebral Peduncle, Pons, andPyramids - ~85% of fibers cross in theDecussation of the Pyramids LMN (2nd order neuron) = in Ventral Horn of spinal cord - Output to skeletal muscles

Question 5

Anterior Corticospinal Tracts

Answer 5

• Motor cortex -> cervical/upper thoracic spinal cord -bilateral for axial musculature control – posture -does NOT cross at the pyramidal decussation, but at level in spinal cord.

Question 6

Anterior Spinocerebellar Tract

Answer 6

• Information about intended movement from lower extremities…inform about activity of inhibitory interneurons 1st Order Neuron = DRG- Fibers travel via Fasiculus Gracilis to… 2nd Order Neuron = Spinal Border Cells- Fibers cross in Anterior White Commissure, ascend via theAnterior Spinocerebellar Tract (via anterior lateral funiculus), cross again in the brainstem, and pass through the Superior Cerebellar Peduncle (SCP) to the Cerebellum

Question 7

Dorsal (Posterior) Spinocerebellar Tract

Answer 7

• Status of individual muscles in the trunk & LOWER limb 1st Order Neuron = DRG - Fibers travel via Fasiculus Gracilisto… 2nd Order Neuron = Clarke’sNucleus (Column) (T1-L2) - Fibers travel rostrally via the DorsalSpinocerebellar Tract (via lateralfuniculus) through the Inferior Cerebellar Peduncle (ICP) and into theCerebellum

Question 8

Cuneocerebellar Tract

Answer 8

• Status of individual muscles in the UPPER limb 1st Order Neuron = DRG - Fibers travel via Fasciculus Cuneatus to… 2nd Order Neuron = Lateral(external) Cuneate Nucleus - Fibers travel rostrally via theCuneocerebellar Tract and throughthe Inferior Cerebellar Peduncle(ICP) to the Cerebellum

Question 9

Medial (Pontine) Reticulospinal Tracta

Answer 9

• Enhances antigravity reflexes Originates in Pons (nucleus reticularis pontis oralis and nucleus reticularis pontis caudalis) No decussation, remains ipsilateral Terminates on All levels of Sp. C. Lamina VIII (VII, IX) -Fas Vol. or cortically induced movements. ↑muscle tone =actions on γMNs

Question 10

Lateral (Medullary) Reticulospinal Tract

Answer 10

• Liberates antigravity muscles from reflex originates in the Medulla (nucleus reticularis gigantocellularis Partial decussation in the Medulla Terminates on All levels of Sp. C. Lamina VII (VI, VIII, IX) - Inhibits voluntary & cortically induced movements. ↓muscle tone by further inhibiting muscle spindle activity =actions on γMNs

Question 11

Medial reticulospinal fibers (Pontoreticulospinal fibers)

Answer 11

Excitatory to extensor motor neurons and to neurons innervating axial musculature Some fibers may inhibit flexor motor neurons

Question 12

Lateral reticulospinal fibers (Bulboreticulospinal fibers)

Answer 12

Inhibitory to extensor motor neurons and neurons innervating muscles of neck and back Some fibers also may excite flexor motor neurons

Question 13

What does this image show?

Answer 13

Medial Lemniscus (Dorsal Column) Pathway

Question 14

What does this image show?

Answer 14

Spinothalamic Pathway

Question 15

What does this image show?

Answer 15

Trigeminal (touch, pressure, proprioception from face)

Question 16

What does this image show?

Answer 16

Trigeminal (pain and temperature from face)

Question 17

What does this image show?

Answer 17

Lateral Corticospinal Tract

Question 18

What does this image show?

Answer 18

Anterior Corticospinal Tract

Question 19

What does this image show?

Answer 19

Medial Lemniscus (Dorsal Column) Pathway

Question 20

What does this image show?`

Answer 20

Substantia Gelatinosa

Question 21

What does this image show?

Answer 21

Spinothalamic Tract

Question 22

What does this image show?

Answer 22

Corticospinal Tract