Geniculate fibers

Geniculate fibers
The motor tract.
*Anatomical terms of neuroanatomy* [edit on Wikidata]

The geniculate fibers are the fibers in the region of the genu of the internal capsule; they originate in the motor part of the cerebral cortex, and, after passing downward through the base of the cerebral peduncle with the cerebrospinal fibers, undergo decussation and end in the motor nuclei of the cranial nerves of the opposite side.

References

This article incorporates text in the public domain from the 20th edition of Gray's Anatomy (1918)

Anatomy of the cerebral cortex of the human brain

Frontal lobe

Superolateral

Prefrontal	Superior frontal gyrus 4 6 8 Middle frontal gyrus 9 10 46 Inferior frontal gyrus: 11 47-Pars orbitalis Broca's area 44-Pars opercularis 45-Pars triangularis Superior frontal sulcus Inferior frontal sulcus

Precentral	Precentral gyrus Precentral sulcus

Medial/inferior

Prefrontal	Superior frontal gyrus 4 6 Medial frontal gyrus 8 9 Paraterminal gyrus/Paraolfactory area 12 Straight gyrus 11 Orbital gyri/Orbitofrontal cortex 10 11 12 Ventromedial prefrontal cortex 10 Subcallosal area 25 Olfactory sulcus Orbital sulcus

Precentral	Paracentral lobule 4 Paracentral sulcus

Both

Parietal lobe

Superolateral	Superior parietal lobule 5 7 Inferior parietal lobule 40-Supramarginal gyrus 39-Angular gyrus Parietal operculum 43 Intraparietal sulcus

Medial/inferior	Paracentral lobule 1 2 3 5 Precuneus 7 Marginal sulcus

Both	Postcentral gyrus/primary somatosensory cortex 1 2 3 Secondary somatosensory cortex 5 Posterior parietal cortex 7

Occipital lobe

Superolateral	Occipital pole of cerebrum Lateral occipital gyrus 18 19 Lunate sulcus Transverse occipital sulcus

Medial/inferior	Visual cortex 17 Cuneus Lingual gyrus Calcarine sulcus

Temporal lobe

Superolateral	Transverse temporal gyrus/Auditory cortex 41 42 Superior temporal gyrus 38 22/Wernicke's area Middle temporal gyrus 21 Superior temporal sulcus

Medial/inferior	Fusiform gyrus 37 Medial temporal lobe 27 28 34 35 36 Inferior temporal gyrus 20 Inferior temporal sulcus

Interlobar
sulci/fissures

Superolateral	Central (frontal+parietal) Lateral (frontal+parietal+temporal) Parieto-occipital Preoccipital notch

Medial/inferior	Medial longitudinal Cingulate (frontal+cingulate) Collateral (temporal+occipital) Callosal sulcus

Limbic lobe

Parahippocampal gyrus	anterior Entorhinal cortex Perirhinal cortex Posterior parahippocampal gyrus Prepyriform area

Cingulate cortex/gyrus	Subgenual area 25 Anterior cingulate 24 32 33 Posterior cingulate 23 31 Isthmus of cingulate gyrus: Retrosplenial cortex 26 29 30

Hippocampal formation	Hippocampal sulcus Fimbria of hippocampus Dentate gyrus Rhinal sulcus

Other	Supracallosal gyrus Uncus Amygdala

Insular cortex

Insular cortex

General

Some categorizations are approximations, and some Brodmann areas span gyri.

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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