Interposed nucleus

Brain: Interposed nucleus
Latin	nucleus interpositus anterior, nucleus interpositus posterior
NeuroLex ID	nlx_anat_20081242

The interposed nucleus is a deep nucleus of the cerebellum and is composed of the globose nuclei and the emboliform nuclei. It is located in the roof (dorsal aspect) of the fourth ventricle, lateral to the fastigial nucleus. It receives its afferent supply from the anterior lobe of the cerebellum and sends output via the superior cerebellar peduncle to the red nucleus.

The interposed nucleus is smaller than the dentate but larger than the fastigial nucleus.

Function

Functionally, it modulates muscle stretch reflexes of distal muscle groups.

Surface anatomy

Lobes	Anterior lobe · Posterior lobe (Horizontal fissure) · Flocculonodular lobe (Flocculus, Nodule) Primary fissure

Medial/lateral	Vermis: anterior (Central lobule, Culmen, Lingula) · posterior (Folium, Tuber, Uvula) · Vallecula of cerebellum Hemisphere: anterior (Alar central lobule) · posterior (Biventer lobule, Cerebellar tonsil)

Deep cerebellar nuclei	Dentate · interposed (Emboliform, Globose) · Fastigial

Cerebellar cortex	Molecular layer (Stellate cell, Basket cell) Purkinje cell layer (Purkinje cell, Bergmann glia cell = Golgi epithelial cell) Granule cell layer (Golgi cell, Granule cell, Unipolar brush cell) Fibers: Mossy fibers · Climbing fiber · Parallel fiber

Internal	Arbor vitae

Peduncles	Inferior (medulla): Dorsal spinocerebellar tract · Olivocerebellar tract · Cuneocerebellar tract · Juxtarestiform body (Vestibulocerebellar tract) Middle (pons): Pontocerebellar fibers Superior (midbrain): Ventral spinocerebellar tract · Dentatothalamic tract · Trigeminocerebellar fibers

anat(n/s/m/p/4/e/b/d/c/a/f/l/g)/phys/devp

noco(m/d/e/h/v/s)/cong/tumr, sysi/epon, injr

proc, drug(N1A/2AB/C/3/4/7A/B/C/D)

Sensory/
ascending

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° (Spinotectal 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

Afferent

Efferent

Bidirectional:
Spinocerebellar

Unc. prop.	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)

anat(n/s/m/p/4/e/b/d/c/a/f/l/g)/phys/devp

noco(m/d/e/h/v/s)/cong/tumr, sysi/epon, injr

proc, drug(N1A/2AB/C/3/4/7A/B/C/D)

anat(h/r/t/c/b/l/s/a)/phys(r)/devp/prot/nttr/nttm/ntrp

noco/auto/cong/tumr, sysi/epon, injr

proc, drug(N1B)