Brain Stem 1

Brain, Encephalon

脑

Classification of the brain: prosencephalon (forebrain) Brain

mesencephalon (midbrain) rhombencephalon (hindbrain)

Telencephalon, cerebrum diencephalon midbrain Pons and cerebellum (metencephalon) Medulla oblongata (myelencephalon) midbrain

Brain stem

pons Medulla oblongata

Section 2

Brain Stem

Ⅰ. External Features 外部形态 Cerebral peduncles

Interpeduncular fossa Root of trigeminal N. cerebellum

Basilar sulcus

olive Anterior median fissure pyramid Bulbopontine sulcus

Anterior view of the braim stem

Decussation of pyramid

External feature

Exteral feature

External feature

Brain Stem anterior view   1. Optic chiasm 2. Optic nerve 3. Optic tract 4. Medial sulcus of the crus cerebri 5. Oculomotor nerve 6. Pons 7. Pyramidal eminence of the pons 8. Retroolivary fossa 9. Oliva 10. Posterolateral sulcus 11. Decusssation of the pyramids 12. Anterolateral sulcus 13. Lateral funiculus 14. Pyramid 15. Foramen caecum 16. Middle cerebellar pedunculus 17. Trigeminal nerve 18. Crus cerebri 19. Interpeduncular fossa, posterior perforate substance 20. Mammillary body 21. Tuber cinereum 22. Infundibulum

External feature Posterior view of the brain stem   1.Pineal gland 2.Thalamus ( Pulvinar ) 3.Superior colliculus 4.Inferior colliculus 5.Lemniscal trigone 6.Frenulum veli 7.Superior medullary velum 8.Median sulcus 9.Gracile tubercle 10.Cuneate tubercle 11.Posterior intermediate sulcus 12.Posteromedian sulcus 13.Vagal trigone 14.Hypoglossal trigone 15.Striae medullares 16.Facial colliculus 17.Locus coeruleus 18.Parabrachial recess 19.Crus cerebri 20.Inferior collicular brachium 21.Medial geniculate body 22.Lateral geniculate body 23.Suoerior collicular brachium 24.Habenula 25.Habenular commissure

External feature

The Brain stem - posterior view , the cerebellum was removed.   1. Middle cerebellar peduncle 2. Superior cerebellar peduncle 3. Inferior cerebellar peduncle 4'.The medullary vestibular area 4''.The pontine vestibular area 5. Medial eminence 6. Facial colliculus 7. Hypoglossal trigone 8. Vagal trigone 9. Area postrema 10. Cinereum tubercle 11. Cuneate tubercle 12. Gracile tubercle 13. Posterolateral sulcus 14. Posterior intermediate sulcus 15. Posteromedian sulcus 16. Obex 17. Fovea inferior 18. Striae medullares 19. Sulcus limitans 20. Fovea superior 21. Locus coeruleus 22. Trochlear nerve 23. Frenulum veli 24. Superior medullary velum

External feature

Brain Stem lateral view   1. Medial geniculate body 2. Inferior collicular brachium 3. Superior colliculus 4. Inferior colliculus 5. Superior cerebellar peduncle 6. Rhomboid Fossa 7. Gracile fascicle 8. Cuneate fascicle 9. Lateral funiculus 10. Pyramid 11. Posterolateral sulcus 12. Oliva 13. Retroolivary fossa 14. Bulbopontine sulcus 15. Pons 16. Trigeminal nerve 17. Lateral sulcus of the crus cerebri 18. Pontomesencephalic sulcus 19. Crus cerebri 20. Optic nerve 21. Optic tract 22. Lateral geniculate body 23. Leminiscal trigone 24. Middle cerebellar peduncle 25. Inferior cerebellar peduncle

External feature

The fourth ventricle

第四脑室

1.Cerebral hemisphere 2.Corpus callosum 3.Thalamus 4.Midbrain 5.Pons 6.Cerebellum 7.Medulla oblongata Brain, Sagittal Section, Medial View

Pons & Cerebellum, Sagittal Section, Medial View

1.Midbrain 2.Cerebellum 3.Pons 4.Medulla oblongata 5.Inferior colliculus 6.Superior medullary velum 7.Fourth ventricle

Ⅱ. Internal structure Cranial nerve nuclei

内部结构 脑神经核

Non-cranial nerve nuclei

非脑神经核

Ascending and descending pathways Reticular formation

上、下行纤维束

网状结构

Cranial nerve nuclei are referred to those nuclei located in the brain stem, where the cranial nerves originate or terminate except the olfactory and optic nerve Non-cranial nerve nuclei are referred to those nuclei which are not linked directly to any cranial nerves functionally or structurally Ascending pathways include 1) pathways originate in the spinal cord and pass the brain stem to higher region of the brain; 2) pathways originate in the brain stem to higher region of the brain Descending pathways originate in the same motor area of the cortex, but terminate in 1) spinal cord and 2) brain stem Reticular formation is recognized as an extensive field of intermingled grey and white matter outside the fiber bundles and nuclei of the brain stem

Development of the spinal cord and brain stem from the neural tube

1) Alar plate posterior horn in SC; nuclei outside sulcus limitans in BS 2) Basal plate anterior horn in SC; nuclei inside sulcus limitans in BS

Cranial nerve nucleus

6 functional columns of cranial nerve nuclei: 1) GSM striated muscles from somites; 2) GVM smooth muscle, cardiac muscle and glands; 3) SVM striated muscles from brachial arches; 4) GSS sensory stimuli from skin and mucosa of head; 5) GVS and SVS visceral sense of thoracic and abdominal organs and taste; 6) SSS stimuli of sound waves and position and movement of head Special somatic sensory nuclei SSS General visceral sensory nuclei GVS Sulcus limitans

Special visceral sensory nuclei SVS General somatic sensory nuclei GSS

General visceral motor nuclei GVM General somatic motor nuclei GSM Special visceral motor nuclei SVM

Cranial nerve nuclei

The composition of 6 functional columns: General somatic motor nuclei: oculomotor N. Trochlear N. abducent N. hypoglossal N. General visceral motor nuclei: accessory nucleus of oculomotor n. Superior salivatory N. inferior salivatory N. dorsal nucleus of vagus n. Special visceral motor nuclei: motor N. of trigeminal n. N. of facial n. Nucleus ambiguus N. of accessory n. General and special visceral sensory nuclei: nucleus of solitary tract General somatic sensory nuclei: spinal N. of trigeninal n. Pontine N. of trigeninal n. Mesencephalic N. of trigeminal n. Special somatic sensory nuclei: vestibular nucleus complex cochlear nuclei

GSM

G,SVS

GVM

GSS

SVM

SSS

Cranial nerve nuclei

Accessory N. oculomoter Oculomotor N.

Motor N. of trigeminal n. Abducent N. Nucleu Of facial n.

Trochlear N. Mesencephalic N. of Ⅴ Pontine N. of Ⅴ

Vestibular N. Cochlear N.

Superior solivatory N. Inferior solivatory N. N. Of solitary tract Hypoglossal N. Nucleus ambiguus Dorsal N. of vagus n.

Spinal N. of trigeminal n. N. Of accessory n.

Cranial nerve nuclei Accessory N. of oculomotor n. oculomotor N. Troclear N. Mesencephalic N. of Ⅴ Motor N. of Ⅴ Pontine N. of Ⅴ N. Of facial n. Vestibular N. Cochlear N. Superior salivatory N. Inferior salivatory N. Dorsal N. of vagus n. N. Of hypoglossal n. N. Of solitary truct Spinal N. of Ⅴ Accessory N.

Some of important non-cranial nerve nuclei Nucleus gracile and nucleus cuneate: relay the fibers of fasciculus gracilis and cuneatus respectively Inferior olivary nuclear complex: a relay station for sensory information ( mainly proprioceptive ) traveling to cerebellum Pontine nuclei: relay stations on the passway from cerebral cortex to the cerebellum Inferior colliculus: reflex centers for auditory responses and concerned in localization of source of sounds Superior colliculus: reflex centers correlating movement of head and eyes and serves to localize and follow visual stimuli. Red nucleus: give off efferent fiber to form the rubrospinal tract and rubrobulbar tract Substantia nigra: its efferent fibers passing to the striatum convey dopamine to cerebrum; its injury will cause Parkinson’s disease

Level of pyramidal decussation

Level of medial lemniscus decussation

Mid-olivary level

Rostral olivary level

Level of facial colliculus

Level of trigeminal n.

Level of inferior colliculus

Level of superior colliculus

Long ascending pathways Passing fibrous bundles which originate in the spinal cord: 1) Medial lemniscus: fibrous bundle formed by relayed fibers from fasciculi gracilis, cuneatus. The fibers relay in gracile and cuneate nuclei, and decussate with fibers of opposite side, finally end in the ventral posteriomedial nucleus of thalamus 2) Spinothalamic lemniscus ： composed of anterior and posterior spinothalamic tracts, and terminate in the ventral posterolateral nucleus of thalamus

Long ascending pathways Fibrous bundles originated in the brain stem: 1) Trigeminal lemniscus: formed by fibers from contralateral spinal and pontine nuclei of trigeminal n. It conducts the tactile, pressure, pain and thermal impulses to the ventral posterolateral nucleus of thalamus 2) Lateral lemniscus: formed by the fibers from the ipsilateral and controlateral cochlear nuclei; some of fibers end in the inferior colliculus, others traverse the brachium of inferior colliculus to the nucleus of medial geniculate body

Long descending pathways Pyramidal tract : descending fiber bundles originated in motor cortex to lower motor neurons in brain stem and spinal cord, It includes 1) corticospinal tract and 2) corticonuclear tract Corticonuclear tract: teminates successively in the motor nuclei of the cranial nerves on both sides of the brain stem except the lower half of facial nucleus and hypoglossal nerve The motor nuclei include the nuclei of general somatic motor and special visceral motor columns: oculomotor n. troclear n. abducent n. hypoglossal n. motor N. of trigeminal n. facial n. nucleus ambiguus and accessory nucleus