Ansa lenticularis

Ansa lenticularis
The image shows dopaminergic pathways of the human brain in normal condition (left) and Parkinsons Disease (right). Red Arrows indicate suppression of the target, blue arrows indicate stimulation of target structure. (Ansa lenticularis visible but not labeled, as red line from GPi to THA.)
Details
Identifiers
Latin	Ansa lentiformis
NeuroNames	hier-427
NeuroLex ID	Ansa lenticularis
TA	A14.1.08.663 A14.1.09.520
FMA	62070
*Anatomical terms of neuroanatomy* [edit on Wikidata]

The ansa lenticularis (ansa lentiformis in older texts) is a part of the brain, making up the superior layer of the substantia innominata of Meynert. Its fibers, derived from the medullary lamina of the lentiform nucleus, pass medially to end in the thalamus and subthalamic region, while others are said to end in the tegmentum and red nucleus.

It is classified by NeuroNames as part of the subthalamus.

References

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

External links

MedEd at Loyola Neuro/nlDEs/nl04s.html

Anatomy of the diencephalon of the human brain

Epithalamus

Surface	Pineal gland Habenula Habenular trigone Habenular commissure

Grey matter	Pretectal area Habenular nuclei Subcommissural organ

Thalamus

Surface	Stria medullaris of thalamus Thalamic reticular nucleus Taenia thalami

Grey matter/ nuclei	paired: AN Ventral VA/VL VP/VPM/VPL Lateral LD LP Pulvinar nuclei Metathalamus MG LG P cell M cell K cell midline: MD Intralaminar Centromedian Midline nuclear group Interthalamic adhesion

White matter	Mammillothalamic fasciculus Pallidothalamic tracts Ansa lenticularis Lenticular fasciculus Thalamic fasciculus PCML Medial lemniscus Trigeminal lemniscus Spinothalamic tract Lateral lemniscus Dentatothalamic tract Acoustic radiation Optic radiation Subthalamic fasciculus Anterior trigeminothalamic tract Medullary laminae

Hypothalamus

Surface

Grey matter

Autonomic zones	Anterior (parasympathetic/heat loss) Posterior (sympathetic/heat conservation)

Endocrine	posterior pituitary: Paraventricular Magnocellular neurosecretory cell Parvocellular neurosecretory cell Supraoptic oxytocin/vasopressin other: Arcuate (dopamine/GHRH) Preoptic (GnRH) Suprachiasmatic (melatonin)

Emotion	Lateral Ventromedial Dorsomedial

White matter

afferent
- Medial forebrain bundle
- Retinohypothalamic tract
efferent

Pituitary

Posterior is diencephalon, but anterior is glandular

Subthalamus

Rostral basal ganglia of the human brain and associated structures

Basal ganglia

Grey matter

Corpus striatum	Dorsal striatum Putamen Caudate nucleus Ventral striatum Nucleus accumbens Olfactory tubercle Globus pallidus GPe GPi

Other	Amygdala Claustrum

White matter

Semioval center

Internal capsule

Corona radiata

Rhinencephalon

Grey matter	Anterior olfactory nucleus Anterior perforated substance Olfactory bulb

White matter	Olfactory tract Medial olfactory stria Lateral olfactory stria Olfactory trigone

Other basal forebrain

Grey matter	Substantia innominata Nucleus basalis of Meynert Nucleus of diagonal band

White matter	Diagonal band of Broca Stria terminalis

Archicortex:
Hippocampal formation/
Hippocampus anatomy

Grey matter	Hippocampus proper CA1 CA2 CA3 CA4 Dentate gyrus Fascia dentata Subiculum

White matter	Alveus Fimbria Perforant path Schaffer collateral

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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