Reticulospinal tract

Reticulospinal tract
Reticulospinal tract is labeled in red, near-center in figure (text tag at left).
Identifiers
NeuroNames	hier-802
NeuroLex ID	Reticulospinal tract
TA	A14.1.04.124
FMA	72639
*Anatomical terms of neuroanatomy* [edit on Wikidata]

The reticulospinal tract (or anterior reticulospinal tract) is an extrapyramidal motor tract that descends from the reticular formation in two tracts to act on the motor neurons supplying the trunk and proximal limb muscles. It is involved mainly in locomotion and postural control, although it does have other effects as well.^[1]

Functions

1. Integrates information from the motor systems to coordinate automatic movements of locomotion and posture

2. Facilitates and inhibits voluntary movement; influences muscle tone

3. Mediates autonomic functions

4. Modulates pain impulses

5. Influences blood flow to lateral geniculate nucleus of the thalamus.

Components

The tract is divided into two parts, the medial (or pontine) and lateral (or medullary) reticulospinal tracts (MRST and LRST).

The MRST is responsible for exciting anti-gravity, extensor muscles. The fibers of this tract arise from the caudal pontine reticular nucleus and the oral pontine reticular nucleus and project to the lamina VII and lamina VIII of the spinal cord (BrainInfo)
The LRST is responsible for inhibiting excitatory axial extensor muscles of movement. The fibers of this tract arise from the medullary reticular formation, mostly from the gigantocellular nucleus, and descend the length of the spinal cord in the anterior part of the lateral column. The tract terminates in lamina VII mostly with some fibers terminating in lamina IX of the spinal cord.

The sensory tract conveying information in the opposite direction is known as the "spinoreticular tract".

Clinical significance

Mostly inhibited by the corticospinal tract, if damage occurs at the level of or below the red nucleus (e.g. to the superior colliculus) it is called decerebration and causes decerebrate rigidity, an unopposed extension of the head and limbs.

The reticulospinal tracts also provide a pathway by which the hypothalamus can control sympathetic thoracolumbar outflow and parasympathetic sacral outflow.

References

↑ FITGERALD, M J Turlough (2012). Clinical Neuroanatomy and Neuroscience. Philadelphia: Saunders Elsevier. p. 192. ISBN 978-0-7020-3738-2.

External links

The spinal cord

General features

Grey matter

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

Anatomy of the pons

Dorsal/
(tegmentum)

Surface

White: Sensory

Medial longitudinal fasciculus
- Vestibulo-oculomotor fibers

White: Motor

Grey: Cranial nuclei

afferent:	GSA Trigeminal Principal Spinal Cochlear nucleus Dorsal Anterior Vestibular nuclei Superior

efferent:	SVE: Trigeminal motor nucleus Facial motor nucleus GSE: Abducens nucleus GVE: Superior salivary nucleus Inferior salivary nucleus

Other	Apneustic center Parabrachial area Pneumotaxic center Subparabrachial nucleus Medial parabrachial nucleus Lateral parabrachial nucleus Superior olivary nucleus Caerulean nucleus

Ventral/
(base)

Grey	Pontine nuclei

White: Motor/descending	Corticospinal tract Corticobulbar tract Corticopontine fibers MCP Pontocerebellar fibers

Surface	Basilar sulcus

Other grey: Raphe/
reticular

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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