Brainstem

Nervous system

brain stem Weihua Yu Department of Anatomy Chongqing Medical University

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Cerebullar development

telencephalon diencephalon

Brain

procerebrum ： telencephalon and diencephalon midbrain ： don’t have obvious change afterbrain ： pons and afterbrain cerebellum marrowbrain ： medulla oblongata

Brain is divide into 6 parts ： telencephalon diencephalon cerebellum mid brain brain stem

brain stem midbrain

pons medulla oblongata

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cerebellum

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The external features of brain stem the shape of brain stem 1. ventral surface of brain stem （ 1 ） medulla oblongata

bulbopontine sulcus pyramid decussation of pyramid olive

（ 2 ） pons

basilar part of pons basilar sulcus middle cerebellar peduncle bulbopontine sulcus

（ 3 ） mid brain cerebral peduncle interpeduncular fossa posterior perforated substance -4-

There are 9 pairs of cranial nerves on ventral surface of brain stem ： ① the oculomotor nerves links with mid brain, and arise from interpeduncular fossa ； ② there are four pairs of cranial nerves links with pons ： trigeminal nerves （ v ） linked with basilar part of pons there are abducent nerve （Ⅵ） ,facial nerve （Ⅶ） and vestibulocochlear nerve （Ⅷ） in the juncture with middle cerebellar peduncle or bulbopontine sulcus from medial to lateral. ③ There are four pairs of cranial nerves linked with medulla oblongata ： glossopharyngeal nerve （Ⅸ）， vagus nerve （Ⅹ） and accessory nerve （Ⅺ） on the dorsal and lateral side of olive from above downward in order. The hypoglossal nerve （Ⅻ） leaves medulla oblongata between pyramids of medulla oblongata and olive. -5-

2. Dorsal surface of brain stem （ 1 ） medulla oblongata gracile tubercle cuneate tubercle inferior cerebellar peduncle （ restiform body ） （ 2 ） pons superior cerebellar peduncle middle cerebellar peduncle （ 3 ） mid brain superior colliculus inferior colliculus quadrigeminal bodies brachium of superior colliculus brachium of inferior colliculus （ 4 ） rhomboid fossa sulcus median 、 sulcus limitans 、 striae medullares 、 medial eminence 、 facial colliculus 、 hypoglossal triangle 、 vagal triangle 、 funiculus separans 、 areas postrema 、 vestibular area 、 acoustic tubercle 、 locus ceruleus 、 obex -6-

3. fourth ventricle of cerebrum medulla oblongata 、 pons and cerebellum Similar to diamond shape The bottom is rhomboid fossa The point exposition to vermis

superior medullary velum inferior medullary velum tela choroidea of fourth ventricle ependyma choroid plexus of fourth ventricle

There are 3 holes on fourth ventricle ： single median aperture of fourth ventricle lies in rhomboid fossa ； paired lateral aperture of fourth ventricle Communicate with subarachnoid space -7-

The internal structure of brain stem Compared with spinal cord, the internal structure of brain stem appears the following characters ： （ 1 ） The structure of medulla oblongata’s inferior part is similar to spinal cord. The central canal still remains, but moves to dorsal gradually. （ 2 ） The gray matter of brain stem don’t continue and form gray column which run lengthwise through the total length of brain stem like that in spinal cord, but get together forming all kinds of nucleus separated with each other. （ 3 ） The nucleus groups of gray substance of spinal cord all link with spinal nerve basically. （ 4 ） The reticular structure appeared in the region between gray matter and white matter has sharp expansion area, and more complex in structure, which contains many important nuclear groups of vital center, such as center of heartbeat, blood pressure and respiratory.

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1. Gray matter of brain stem Nuclei of cranial nerves “non-nuclei of cranial nerves” relay nucleus reticular nucleus

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（ 1 ） nuclei of cranial nerves

somatic motor fiber visceral motor fiber visceral sensory fiber somatic sensory fiber

（ 1 ） general motor nucleus 4 pairs dominate skeletal muscle （ lingual muscle ， extraocular muscles ） nucleus of oculomotor nerve nucleus of trochlear nerve nucleus of abducent nerve hypoglossal nucleus

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（ 2 ） special visceral motor nucleus 4 pairs Dominate the skeletal muscle evolved from branchial arch masseter muscle 、 muscles 、 soft palate 、 pharyngeal muscle 、 laryngeal muscle motor nucleus of trigeminal nerve facial nucleus ambiguous nucleus accessory nucleus

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（ 3 ） general visceral motor nucleus ： 4 pairs Dominate smooth muscle 、 cardiac muscle and glands accessory nucleus of oculomotor nerve superior salivatory nucleus inferior salivatory nucleus dorsal nucleus of vagus

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（ 4 ） general visceral sensory nucleus ： 1 pair receive the sensory fiber of organ and cardiovascular the lower half of solitary nucleus

（ 5 ） special visceral sensory nucleus receive taste fibers the capitular head of solitary nucleus

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（ 6 ） general somatic sensory nucleus ： 1 pair

Receive sensory fiber of skin on head and face and mucosa in oral and nasal cavity mesencephalic nucleus of trigeminal nerve ： the proprioceptive sense of masseter muscle pontine nucleus of trigeminal nerve ： tactile sense spinal nucleus of trigeminal nerve ： sense of pain and warm -14-

（ 7 ） special somatic sensory nucleus Receive the fiber of auditory or equilibratory sensation.

vestibular nucleus （ superior nucleus 、 interior 、 lateral nuclear 、 inferior nucleus ） cochlear nucleus dorsal nucleus of cochlear nerve ventral nucleus of cochlear nerve （ anterior nucleus 、 posterior nucleus) -15-

According to the nature and function, 6 functional columns arrange longitudinally in brain stem according to the following laws ：  In the gray matter of the bottom of fourth ventricle of cerebrum, the motor nucleus and columns are interior to sulcus limitans ， while the sensory nucleus and columns lie lateral to sulcus limitans ；  from median line to two sides are general somatic motor column, general visceral motor column, general and special visceral sensory column and special somatic sensory column.  Special visceral column and general somatic sensory column are ventrolateral to gray matter of pavimentum ventriculi, or in reticular structure.

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2 、 non-nuclei of cranial nerves 1 ） medulla oblongata （ 1 ） gracile nucleus cuneate nucleus （ medial lemniscus ）

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（ 2 ） inferior olivary nucleus ： participate in the controlling of cerebellum on motor olivocerebellar tract→inferior cerebellar peduncle enter into cerebellum （ 3 ） accessory cuneate nucleus cuneocerebellar tract→inferior cerebellar peduncle enter into cerebellum

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2 ） Pons （ 1 ） superior olivary nucleus enter into lateral lemniscus and participate in tone localization

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（ 2 ） nuclei of pons pontocerebellar fibers→middle cerebellar peduncle enter into cerebellum The relay station of these fibers connects cerebral cortex with cerebellum cortex.

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（ 3 ） nucleus of lateral lemniscus lateral lemniscus

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3 ） mid brain （ 1 ） inferior colliculus receive the termination of lateral lemniscus ， auditory reflex center （ 2 ） superior colliculus visual reflex center ， tectospinal tract emited from superior colliculus

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（ 3 ） pretectal area lies in the symphyses of mid brain with diencephalon, an area between commissura posterior and superior colliculus

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（ 4 ） red nucleus ： receive the projection of dentate body of cerebellum receive the corticocerebral projection send out fibers to spinal cord — rubrospinal tract send out fibers to inferior olivary nucleus （ 5 ） substantia nigra produce dopamine→ neostriatum （ 6 ） ventral tegmental area the deep surface of interpeduncular fossa contains dopamine neurons, which participates in the regulation of voluntary movements

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white matter fiber bundles

long preceding fiber bundles long descending fiber bundles

1 、 long preceding fiber bundles medial lemniscus spinal lemniscus trigeminal lemniscus lateral lemniscus anterior spinocerebellar tract posterior spinocerebellar tract medial longitudinal fasciculus

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1 ） medial lemniscus→nucleus ventralis posterolateralis thalami

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1 ） medial lemniscus

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1 ） medial lemniscus

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1 ） medial lemniscus

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1 ） medial lemniscus

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1 ） medial lemniscus The sensory conductive pathway

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2 ） spinothalamic tract （ spinal lemniscus ） nucleus ventralis posterolateralis thalami

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2 ） spinothalamic tract （ spinal lemniscus ）

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2 ） spinothalamic tract （ spinal lemniscus ）

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2 ） spinothalamic tract （ spinal lemniscus ）

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2 ） spinothalamic tract （ spinal lemniscus ）

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2 ） spinothalamic tract （ spinal lemniscus ）

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3 ） spinal lemniscus →nucleus ventralis posteromedialis thalami

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3 ） trigeminal lemniscus

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3 ） trigeminal lemniscus

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3 ） trigeminal lemniscus

the conductive pathway

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4 ） lateral lemniscus arises from the auditory fibers of superior olivary nucleus on two sides and dorsal cochlear nucleus as well as ventral cochlear nucleus of opposite side. The lateral lemniscus turns upward on the lateral superior olivary nucleus and forms lateral lemniscus→inferior colliculus→medial geniculate body

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4 ） lateral lemniscus

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4 ） lateral lemniscus

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4 ） lateral lemniscus trapezoid body The auditory fibers of superior olivary nucleus and ventral cochlear nucleus runs transversely in the inferior middle part of pons, then crosses above median line and forms trapezoid body. Some trapezoid body fibers turn upward and join lateral lemniscus.

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4 ） lateral lemniscus the conductive pathway

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5 ） posterior spinocerebellar tract

posterior spinocerebellar tract→ inferior cerebellar peduncle →enter into cerebellum

anterior spinocerebellar tract→ascending via superior cerebellar peduncle →enter into cerebellum

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6 ） medical longitudinal fasciculus these fibers derived from vestibular nucleus go upward and downward along median line. preceding fiber→extraocular muscles motor nucleus descending fiber→cervical cord segment→intermedial zone and medial part of anterior horn

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2 、 long descending fiber bundle pyramidal tract rubrospinal tract tectospinal tract vestibulospinal tract reticulospinal tract

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1 ） pyramidal tract

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corticonuclear tract corticospinal tract

1 ） pyramidal tract

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corticonuclear tract corticospinal tract

1 ） pyramidal tract

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corticonuclear tract corticospinal tract

1 ） pyramidal tract

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corticonuclear tract corticospinal tract

1 ） pyramidal tract

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corticonuclear tract corticospinal tract

1 ） pyramidal tract

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corticonuclear tract corticospinal tract

2 ） tectospinal tract

3 ） rubrospinal tract

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4 ） vestibulospinal tract

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3 、 reticular formation of brain stem There are lots of pericaryon in central region of brain stem. The fibers arranged in a cross pattern, which constitutes reticular formation of brain stem.

the main nucleus groups of reticular formation of brain stem 1 ） the nuclear groups project to cerebellum 2 ） raphe nuclei groups 3 ） the reacting region of medial nucleus 4 ） the reception region of lateral nuclear group -58-