Ascending Sensory Tracts

Question 1

What are the 7 ascending tracts? Where are they going and coming from? And what kind of info are they ALL carrying?

Answer 1

Ascending Tracts to the Brain/ Cortex

1. Posterior column medial leminscus or Dorsal column medial leminiscus (PCML) sensory
2. Lateral spinothalamic tract (LST): sensory
3. Anterior spinothalamic tract (AST): sensory

Ascending tracts to the Cerebellum

1. Posterior spinocerebellar tract (PSCT): sensory
2. Anterior spinocerebellar tract (ASCT): sensory
3. Cunecerebellar tract (CCT): sensory
4. Rubrospinocerebellar (RSCT): sensory (spinal reflex circuits)

Question 2

What is the PCML? What info does is carry? What is it’s path?

Answer 2

ASCENDING TO Brainstem/Thalamus/ Cortex

• Posterior Column-Medial Lemniscus (BS) Tract (PC-ML) AKA Dorsal Columns
  
  • Carries information about Discriminative or Fine Touch, Pressure, Vibration, Stereognosis and Proprioception/Kinesthesia (moving sense through space)
  • Dorsal Columns (Posterior Spinal Cord) contain Fasciculus Gracilis (LES) and Fasciculus Cuneatus (UES)

Posterior Column-Medial Lemniscus Tract (PC-ML) AKA Dorsal Columns

• • Skin and Joint Receptors send information along Sensory Spinal Nerve to Dorsal Root Ganglion (DRG) to Dorsal Root to Spinal Cord
    
    • To Dorsal Columns AKA Posterior Columns AKA
    • Fasciculus Gracilis (LES) and Fasciculus Cuneatus (UES)
    • To Cell Bodies in Brainstem Medulla to Nucleus Gracilis and Nucleus Cuneatus
    • Fibers then DECUSSATE in Medulla to form Medial Lemniscus
    • Ascends to VPL in Thalamus to Internal Capsule
    • To Primary Somatosensory Cortex or Postcentral Gyrus (Recall Initial Reception of Somatosensation)

Question 3

What are the deficits of a PCML lesion in the SC? Above the Medulla?

Answer 3

• Posterior Column-Medial Lemniscus (PC-ML) Lesion
  
  • Loss of Discriminative Touch, Vibration, Proprioception
  • Complete Lesion at Spinal Cord
    
    • Bilateral Loss
  • Hemi-Lesion at Spinal Cord
    
    • Ipsilateral Loss (Due to Decussation in Medulla)
  • Hemi-Lesion at Medulla or Cerebral Cortex
    
    • Contralateral Loss (Due to Decussation at Brainstem or higher)

Question 4

What is the LST carry and what is it’s path?

Answer 4

ASCENDING TO Brainstem/Thalamus/ Cortex

• Lateral Spinothalamic Tract (LST)
  
  • Carries information about Pain and Temperature

Lateral Spinothalamic Tract (LST)

• • Skin Receptors send information along Sensory Spinal Nerve to Dorsal Root Ganglion (DRG) to Dorsal Root to Lissauer’s Tracts to Dorsal Horn in Spinal Cord
    
    • LST then DECUSSATES in Spinal Cord to Anterior Funiculi and Lateral Funiculi AKA Anterolateral Pathway (decussates right away at the spinal cord level)
    • Ascends to Brainstem and joins PC-ML Tract
    • Ascends to VPL in Thalamus to Internal Capsule
    • To Primary Somatosensory Cortex or Postcentral Gyrus

(Recall Initial Reception of Somatosensation)

Question 5

What is the presentation of a lesion at the LST in the SC? In the Cortex?

Answer 5

• Lateral Spinothalamic Tract Lesion
• Loss of Pain and Temperature Senses
  
  • Hemi-Lesion at Brainstem or Cerebral Cortex
    
    • Contralateral Loss (Decussation in Spinal Cord)
  • Complete Injury at Spinal Cord
    
    • Bilateral Loss
  • Hemi-Lesion at Spinal Cord
    
    • Contralateral Loss Below Level of Lesion
    • (Decussation occurs in Spinal Cord)

Question 6

What is the AST? What info does it carry? What is it’s path?

Answer 6

• ASCENDING TO Brainstem/Thalamus/Cortex
  
  • Anterior Spinothalamic Tract (AST)
    
    • Carries information about Conscious Crude Touch, Light Touch, Pain and Temperature
• • Skin Receptors send information along Sensory Spinal Nerve to Dorsal Root Ganglion (DRG) to Dorsal Root to Dorsal Horn in Spinal Cord
    
    • AST then DECUSSATES in Spinal Cord to Anterior Funiculi and Posterolateral Funiculi
    • Ascends to Brainstem
    • Ascends to VPL in Thalamus to Internal Capsule
    • To Primary Somatosensory Cortex or Postcentral Gyrus

(Recall Initial Reception of Somatosensation

Question 7

What is the PSCT? What is it carrying? What is it’s path?

Answer 7

ASCENDING TO Cerebellum

• Posterior Spinocerebellar Tract (PSCT) or Dorsal Spinocerebellar
  
  • Carries information about Unconscious Lower Extremity (LE) Proprioception, Muscle Tone in Skeletal Muscle, and Coordination of Individual Muscles
• • Muscle Spindle, GTOs (Golgi Tendon Organs), Joint Receptors send information along Sensory Spinal Nerve to Dorsal Roots to Dorsal Columns (Fasciculus Gracilis(LE info housed)
    
    • Synapses in Spinal Cord with Clarke’s Nucleus in Gray Matter at T12 and ascends Posterolateral Funiculus IPSILATERALLY to Brainstem
    • Through Inferior Cerebellar Peduncle to Cerebellum

Question 8

What is the presentation if there is a lesion of the PSCT in the SC? Cortex?

Answer 8

• Spinocerebellar Tract Lesion
  
  • Loss of Proprioception and Postural Control
  • Lesion in Cerebellar Cortex
    
    • Ipsilateral Loss
  • Complete Lesion at Spinal Cord
    
    • Bilateral Loss

Question 9

What is the ASCT? Fernonand Mondego? What does it carry? What is it’s path?

Answer 9

ASCENDING TO Cerebellum

• Anterior Spinocerebellar Tract (ASCT) or Ventral Spinocerebellar
  
  • Carries information about Unconscious Lower Extremity (LE) Proprioception, Muscle Tone in Skeletal Muscle, and Coordination of Individual Muscles

Pathway ** Double CROSSES**

• Muscle Spindle, GTOs, Joint Receptors send information along Sensory Spinal Nerve to Dorsal Roots
• DECUSSATES (1^st cross) in Spinal Cord to Lateral Funiculus
• Ascends to Brainstem
• DECUSSATES (2^nd cross) at Superior Cerebellar Peduncle to
• Cerebellum

Question 10

What happens if there is a lesion of the ASCT?

Answer 10

• Hemi-Lesion at Spinal Cord
  
  • Anterior Spinal Cerebellar Tract (double crosser)
  • Contralateral Loss Below Level of Lesion (Due to First Decussation at Level of Spinal Cord from Dorsal Horn to Lateral Funiculi and not at Second Decussation at Superior Cerebellar Peduncle)

Question 11

What is the CCT? What does it carry? What is it’s path?

Answer 11

ASCENDING TO Cerebellum

Cuneocerebellar Tract (CCT)

• Carries information about Unconscious Upper Extremity (UE) Proprioception, Muscle Tone in Skeletal Muscle, and Coordination of Trunk and Limbs
• • Muscle Spindle, GTOs, Joint Receptors send information along Sensory Spinal Nerve to Dorsal Roots
    
    • Ascends IPSILATERALLY via Posterolateral Funiculus
    • To synapse with Nucleus Cuneatus in Brainstem
    • Through Inferior Cerebellar Peduncle to Cerebellum
    • (Runs with PSCT)

Question 12

What is the RSCT? Path? info?

Answer 12

ASCENDING TO Cerebellum

Rostrospinocerebellar Tract (RSCT)

• Carries information about spinal reflex circuits
• Pathway
  
  • Receptors to Cervical Spinal Cord Levels to Inferior and Superior Cerebellar Peduncles
• ISPSILATERALLY through Brainstem into Cerebellum