Spinoreticular tract

Spinoreticular tract
Details
Identifiers
Latin	tractus spinoreticularis
TA	A14.1.02.231
FMA	75693
*Anatomical terminology* [edit on Wikidata]

The spinoreticular tract is an ascending pathway in the white matter of the spinal cord, positioned closely to the lateral spinothalamic tract. The tract is from spinal cord—to reticular formation^[1]— to thalamus.

It is responsible for automatic responses to pain, such as in the case of injury.

Pathway

The spinoreticular tract utilizes four levels of neurons, unlike most ascending tracts which have first- through third-order neurons. The tract begins with first-order neurons, which immediately synapse with second-order neurons in the posterior horn of the spinal column. These neurons decussate to the opposite side (anterolateral), and travel up the spinal column. It terminates in the brainstem at the medullary-pontine reticular formation. Information is sent from there to the intradmedian nucleus of the thalamic intralaminar nuclei. The thalamic intralaminar nuclei project diffusely to entire cerebral cortex where pain reaches conscious level and promotes behavioral arousal.It is believed that spinoreticular tract projects to neurons having a large receptive fields that may cover wide areas of the body and play a role in the memory and in the affective (emotional) component of pain.

It is still undetermined if the spinoreticular tract possesses ipsilateral fibers in addition to those that decussate. It is hypothesized that during development the tract was bilateral, but that the ipsilateral synapses became ineffective during development.

References

↑ "Chapter 25:Neural Mechanisms of Cardiac Pain: The Anterolateral System". Retrieved 2009-11-26.

Saladin, Kenneth S. Anatomy & Physiology: The Unity of Form and Function. New York: McGraw-Hill. 2010.
Mense, Siegfried & Gerwin, Robert D. Muscle Pain: Understanding and Mechanisms. New York: Springer. 2010.
Julien N, Goffaux P, Arsenault P, et al. Widespread pain in fibromyalgia is related to a deficit

of endogenous pain inhibition. Pain 2005;114(1–2):295–302.

Posterior grey column	Marginal nucleus Substantia gelatinosa of Rolando Nucleus proprius Spinal lamina V Spinal lamina VI

Lateral grey column	Intermediolateral nucleus Posterior thoracic nucleus

Anterior grey column	Interneuron Alpha motor neuron Onuf's nucleus

Other	Rexed laminae Central gelatinous substance Gray commissure Central canal Terminal ventricle

White matter

Sensory

Posterior	Posterior column-medial lemniscus pathway: Gracile Cuneate

Lateral:	Spinocerebellar dorsal ventral Spinothalamic lateral anterior Posterolateral Spinotectal

Spinoreticular tract Spino-olivary tract

Motor

Lateral	Corticospinal Lateral Extrapyramidal Rubrospinal Olivospinal Raphespinal

Anterior	Corticospinal Anterior Extrapyramidal Vestibulospinal Reticulospinal Tectospinal

Both

Anterior white commissure

External features

Ventral
- Anterior median fissure
- Anterolateral sulcus
Dorsal
- Posterior median sulcus
- Posterolateral sulcus

Brain and spinal cord: neural tracts and fasciculi

Sensory/
ascending

PCML

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/
descending

Pyramidal

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

Extrapyramidal

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

Midbrain tectum → Tectospinal tract → muscles of neck

Basal ganglia

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

Cerebellar

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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Spinoreticular tract

Pathway

References

Further reading