Posterior Longitudinal Fasciculus
The posterior longitudinal fasciculus (Schütz’s bundle) contains ascending and descending fiber systems
that connect the hypothalamus with various nuclei of the brain stem and provide
connections between the visceroefferent parasym-pathetic nuclei. A large
portion of the fibers are peptidergic (somatostatin, among others). They
originate or terminate, respec-tively, in the septum, the oral hypothalamus,
the gray tubercle (B13), and the mamillarybodies (B14).
They aggregate in the mid-brain below the ependyma of the aqueduct and form the
longitudinal fasciculus, which runs beneath the ependyma on the floor of the
fourth ven-tricle to the lower portion of the medulla oblongata.
Fibers
branch off to the superior colliculi
(B15) and to the parasympathetic
nuclei, namely, the Edinger – Westphal
nucleus (ac-cessory nucleus of oculomotor nerve) (B16), the superior (B17) and inferior (B18) sali-vatory nuclei, and the posterior vagus nu-cleus (B19). Other fibers terminate in
thecranial nerve nuclei, namely, in the motornucleus
of the trigeminal nerve (B20),
the fa-cial nucleus (B21), and the hypoglossal nu-cleus (B22).
Fibers are also exchanged withthe nuclei of the reticular formation.
The
posterior longitudinal fascicle receives olfactory impulses via the lateroposteriortegmental nucleus (habenular
nucleus – in-terpeduncular nucleus – lateroposterior tegmental nucleus).
Long ascending pathways.Fibers, probablytaste fibers,
ascend from the solitary nucleus (B23) to the hypothalamus. The fibers of
serotoninergic neurons can be traced by fluorescence microscopy from the posteriorraphe nucleus (B24) into the region of theseptum.
The
posterior longitudinal fasciculus re-ceives hypothalamic, olfactory, and
gustatory impulses that are relayed to the motor and sensory nuclei of the
brain stem (reflex movement of the tongue, secretion of saliva).
A25
Subthalamic nucleus.
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