red nucleus, nucleus niagra. ..

Location of gracilis and cuneatus nuclei

Posterior part of medulla oblongata,

in the depth of homonymous tubercles (cranial end of gracilis and cuneatus fasciculi)

Function of gracilis and cuneatus nuclei

Contain 2nd order neurons of discriminative touch and kinesthetic pathways of trunk and limbs

Course of fibers from gracilis and cuneatus nuclei

Form internal arcuate fibers → curve around central grey matter → cross midline (sensory decussation) → ascend in medial lemniscus to 3rd order neurons

Accessory cuneatus nucleus: location & function

Located dorsolateral to cuneatus nucleus

→ contains 2nd order neurons of proprioceptive pathways

→ sends fibers to cerebellum (cuneo-cerebellar tract)

Location of inferior olivary complex

Lateral part of medulla oblongata → in the depth of the olive

Components of inferior olivary complex

Inferior olivary nucleus,

Medial accessory olivary nucleus,

Dorsal accessory olivary nucleus

Structure of inferior olivary nucleus

C-shaped crenated lamina of grey matter (like a crumpled bag, hilum directed medially)

Function of inferior olivary complex

Motor coordination; receives input from

cerebral cortex,

red nucleus,

spinal cord → sends fibers to cerebellum via inferior cerebellar peduncle

Location of substantia nigra

Throughout midbrain, between tegmentum and crus cerebri

Relation of oculomotor nerve to substantia nigra

Fibers pass through its medial part to reach apparent origin at medial aspect of cerebral peduncle (interpeduncular fossa)

Shape and parts of substantia nigra

Semilunar-shaped; 2 parts: Pars reticulata, Pars compacta

Pars reticulata: features

Adjacent to crus cerebri

contains GABAergic neurons

projects to VA & MD thalamic nuclei, superior colliculus, reticular substance

Pars compacta: features

Adjacent to tegmentum; dopaminergic neurons with melanin; projects mainly to neostriatum, less to globus pallidus and subthalamic nucleus

Connections of substantia nigra

Bilaterally connected to corpus striatum; also sends fibers to thalamus and superior colliculus

Function & clinical relevance of substantia nigra ( pars compacta )

Motor control (extrapyramidal system)

dopaminergic neurons affected in Parkinson disease

Location of red nucleus

Upper midbrain

in tegmentum → medial to substantia nigra

Structures posterolateral to red nucleus

Lemnisci: medial, trigeminal, and spinal

Shape and parts of red nucleus

Ovoid; 2 parts

Magnocellular (caudal, phylogenetically older)

Parvocellular (cranial, phylogenetically newer)

Functions and connections of red nucleus

Part of extrapyramidal system; receives input from cerebellum and cerebral cortex

→ sends: Inputs to cerebellum (directly or via inferior olivary complex),

Fibers to spinal cord (rubrospinal fasciculus for upper limb movement)