Tracts and nuclei of the medula oblongata Mrk

Tracts and nuclei of the medula oblongata Márk Kozsurek, M. D. , Ph. D. www. flickr. com/photos/ethanhein/2972774132/sizes/o/in/photostream/ ED II. , 03/10/2017

lateral view posterior view Two sections through the medulla

n Nuclei (cell bodies of neurons – gray matter) n cranial nerve nuclei n sensory – somatosensory or viscerosensory n motor – somatomotor, branchialmotor or visceromotor n n other nuclei (not related to cranial nerves) Tracts (axons – white matter) ascending sensory n desceding motor n

Sensory systems

Motor systems Pyramidal system simple structure voluntary movements Extrapyramidal tracts complex network body balance muscle tone automatic movements

Originally sensory nerons are found in the dorsal portion of the neural tube (alar plate), while motor neurons occupy the ventral part (basal plate). As the fourth ventricle „opens up”, sensory nuclei migrate laterally and motor cells move dorsomedially.

Medulla oblongata caudal („closed”) part, approx. at the level of obex

lateral view posterior view

2 sensory and 2 motor cranial nerve nuclei

Sol STN XII Amb Sol: solitary nucleus Amb: ambiquus nucleus STN: spinal trigeminal nucleus

Cu G r Sol STN XII Amb inf. olivary nucl. Sol: solitary nucleus Amb: ambiquus nucleus STN: spinal trigeminal nucleus Gr: gracile nucleus Cu: cuneate nucleus

Cu G r Sol STN st t XII Amb inf. olivary nucl. STT medial lemniscu s stt: spinal trigeminal tract STT: spinothalamic tract

Cu G r st t Sol STN XII Amb STT inf. olivary nucl. Py stt: spinal trigeminal tract STT: spinothalamic tract

n n The caudal solitary nucleus (lateral nucl. of ala cinerea) receives general viscerosensory input from cervical, thoracic and abdominal organs. Spinal trigeminal nucleus (general somatosensory nucleus of CNs V, VII, IX, X) receives protopathic information from the head via the spinal trigeminal tract which is constituted by the central axons of the pseudounipolar neurons of the corresponding ganglia. Motoneurons within the hypoglossal nucleus (a general motor nucleus) innervate the muscles of the tongue and contribute to the innervation of the infrahyoid muscles. Ambiquus nucleus is the branchialmotor nucleus of the CNs IX, X, XI contributing to the innervation of the striated muscles of the pharynx, larynx, esophagus.

n n n Gracile and cuneate nuclei are the brainstem relay nuclei of the dorsal column-medial lemniscus pathway conveying epicritic information. Fibres arising from these nuclei decussate and ascend close to the midline as the medial lemniscus toward the thalamus. Spinothalamic tract (pain and heat sensation) arises from the dorsal spinal cord and terminates in the thalamus. 80 -90% of the pyramidal tract fibres decussate in the caudal medulla and descend in the lateral funiculus of the spinal cord.

http: //semmelweis. hu/anatomia/files/2014/04/Brainstem-sections. pdf

Medulla oblongata rostral („open”) part, accross the hypoglossal and vagal trigones

lateral view posterior view

One more cranial nerve nucleus!

NDX: dorsal vagus nucleus NDX Sol vagus n. STN Amb hypoglossus n. XII inferior cerebellar peduncle

NDX: dorsal vagus nucleus Gr Cu Sol vagus n. STN Amb inf. olivary nucl. hypoglossus n. NDX XII inferior cerebellar peduncle

NDX: dorsal vagus nucleus Gr Cu Sol NDX XII vagus n. STN inferior cerebellar peduncle st t STT Amb inf. olivary nucl. hypoglossus n. dsc vsc medial lemniscu s dsc: dorsal spinocerebellar tract vsc: ventral spinocerebellar tract

NDX: dorsal vagus nucleus Gr Cu Sol inferior cerebellar peduncle NDX XII MLF vagus n. STN TST st t STT Amb dsc vsc ML inf. olivary nucl. Py hypoglossus n. dsc: dorsal spinocerebellar tract vsc: ventral spinocerebellar tract

Moving upward, what is new? n n n Within the vagus complex beside the solitary nucleus the dorsal vagal nucleus appears. This general visceromotor nucleus provides parasympathetic fibres for the viscera of the neck, thorax and abdomen. Inferior olivary nucleus is mainly involved in extrapyramidal functions. Dorsal (Flechsig) and ventral (Gowers) spinocerebellar tracts carry proprioceptive and epicritic information from the spinal cord to the cerebellum. Median longitudinal fascicle (MLF) is a part of the extrapyramidal system, connects the brainstem gaze centers, the nuclei of C. N. III, IV and VI, the vestibular apparatus and the cervical spinal motoneurons innervating the muscles of the neck (coordination of eye and head movement). Tectospinal tract (TST): extrapyramidal patway from the

http: //semmelweis. hu/anatomia/files/2014/04/Brainstem-sections. pdf

Reticular formation Diffuse network of neurons that occupies the whole brainstem around the major descending and ascending pathways and cranial nerve nuclei. n Motor functions (muscle tone, posture, gaze, swallowing, breathing, vomiting, coughing, sneezing) n Cardiovascular regulation n Pain modulation n ARAS: ascending activating reticular system – consciousness, sleeping, arousal

Three longitudinal columns of nuclei in the midline, medially and laterally.

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