Extrapyramidal

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Extra means outside. (Lat.) extra = outside, and pyramidal (q.v.), hence descending nerve tracts that do not traverse the pyramids of the medulla.

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General features

* Cervical enlargement

Posterior grey column	* Marginal nucleus Substantia gelatinosa of Rolando Nucleus proprius Rexed lamina V Rexed lamina VI
Lateral grey column	* Intermediolateral nucleus Posterior thoracic nucleus
Anterior grey column	* Interneuron Alpha motor neuron Onuf's nucleus Gamma motor neuron
Other	* Rexed laminae Central gelatinous substance Gray commissure

Sensory

Posterior	* Posterior column-medial lemniscus pathway Gracile Cuneate
Lateral	* Spinocerebellar dorsal ventral Spinothalamic lateral anterior Posterolateral Spinotectal
Anterior	* Spinoreticular tract Spino-olivary tract

Motor

Lateral	* Corticospinal Lateral Extrapyramidal Rubrospinal Raphespinal Reticulospinal Hypothalamospinal
Anterior	* Corticospinal Anterior Extrapyramidal Vestibulospinal Reticulospinal Tectospinal Raphespinal Olivospinal

Both

* Anterior white commissure

Brain and spinal cord: neural tracts and fasciculi

Sensory

1°:	* Pacinian corpuscle/Meissner's corpuscle → Posterior column (Gracile fasciculus/Cuneate fasciculus) → Gracile nucleus/Cuneate nucleus
2°:	* → sensory decussation/arcuate fibers (Posterior external arcuate fibers, Internal arcuate fibers) → Medial lemniscus/Trigeminal lemniscus → Thalamus (VPL, VPM)
3°:	* → Posterior limb of internal capsule → Postcentral gyrus

Anterolateral/
pain

Fast/lateral	* 1° (Free nerve ending → A delta fiber) → 2° (Anterior white commissure → Lateral and Anterior Spinothalamic tract → Spinal lemniscus → VPL of Thalamus) → 3° (Postcentral gyrus) → 4° (Posterior parietal cortex) 2° (Spinomesencephalic tract → Superior colliculus of Midbrain tectum)
Slow/medial	* 1° (Group C nerve fiber → Spinoreticular tract → Reticular formation) → 2° (MD of Thalamus) → 3° (Cingulate cortex)

Motor

* flexion: Primary motor cortex → Posterior limb of internal capsule → Decussation of pyramids → Corticospinal tract (Lateral, Anterior) → Neuromuscular junction

flexion:	* Primary motor cortex → Genu of internal capsule → Corticobulbar tract → Facial motor nucleus → Facial muscles
flexion:	* Red nucleus → Rubrospinal tract
extension:	* Vestibulocerebellum → Vestibular nuclei → Vestibulospinal tract
extension:	* Vestibulocerebellum → Reticular formation → Reticulospinal tract

direct:	1° (Motor cortex → Striatum) → 2° (GPi) → 3° (Lenticular fasciculus/Ansa lenticularis → Thalamic fasciculus → VL of Thalamus) → 4° (Thalamocortical radiations → Supplementary motor area) → 5° (Motor cortex)
indirect:	1° (Motor cortex → Striatum) → 2° (GPe) → 3° (Subthalamic fasciculus → Subthalamic nucleus) → 4° (Subthalamic fasciculus → GPi) → 5° (Lenticular fasciculus/Ansa lenticularis → Thalamic fasciculus → VL of Thalamus) → 6° (Thalamocortical radiations → Supplementary motor area) → 7° (Motor cortex)
nigrostriatal pathway:	* Pars compacta → Striatum

Afferent

* Vestibular nuclei → Vestibulocerebellar tract → ICP → Cerebellum → Granule cell

Pontine nuclei → Pontocerebellar fibers → MCP → Deep cerebellar nuclei → Granule cell

Inferior olivary nucleus → Olivocerebellar tract → ICP → Hemisphere → Purkinje cell → Deep cerebellar nuclei

Efferent

* Dentate nucleus in Lateral hemisphere/pontocerebellum → SCP → Dentatothalamic tract → Thalamus (VL) → Motor cortex

Interposed nucleus in Intermediate hemisphere/spinocerebellum → SCP → Reticular formation, or → Cerebellothalamic tract → Red nucleus → Thalamus (VL) → Motor cortex

Fastigial nucleus in Flocculonodular lobe/vestibulocerebellum → Vestibulocerebellar tract → Vestibular nuclei

Bidirectional:
Spinocerebellar

Unconscious proprioception	* lower limb → 1° (muscle spindles → DRG) → 2° (Posterior thoracic nucleus → Dorsal/posterior spinocerebellar tract → ICP → Cerebellar vermis) upper limb → 1° (muscle spindles → DRG) → 2° (Accessory cuneate nucleus → Cuneocerebellar tract → ICP → Anterior lobe of cerebellum)
Reflex arc	* lower limb → 1° (Golgi tendon organ) → 2° (Ventral/anterior spinocerebellar tract→ SCP → Cerebellar vermis) upper limb → 1° (Golgi tendon organ) → 2° (Rostral spinocerebellar tract → ICP → Cerebellum)

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