1. Brain stem

2. The brain stem
Consists of
Midbrain
Pons
Medulla oblongata 1 2 3

3. Medulla oblongata Ventral surface
Pyramid: contains pyramidal tract (corticospinal tract)
Decussation of pyramid: formed by crossing fibers of corticospinal tract
Olive: produced by underlying inferior olivary nucleus
Anterolateral sulcus: rootlets of hypoglossal nerve emerge from it
Retroolivary sulcus: rootlets of glossopharyngeal, vagus and accessory nerves emerge from it 1 IX
XII 3 X XI 4 5 2

4. Medulla oblongata Dorsal surface Lower portion
Gracile tubercle: produced by underlying gracile nucleus
Cuneate tubercle: marks the site of cuneate nucleus
Inferior cerebellar peduncle
Obex
Upper portion: forms the lower half of rhomboid fossa 3 5 2 4 1

5. Pons Ventral surface Basilar part (1) Basilar sulcus (2)
Bulbopontine sulcus (3): from medial to lateral, the abducent, facial and vestibulocochlear nerves appear
Middle cerebellar peduncle (4)
Trigeminal nerve (5) 1 V 5 2 VI 4
VII 3
VIII

6. Pons Dorsal surface Superior cerebellar peduncle (1)
Superior medullary velum (2)
Forms the upper half of rhomboid fossa 2 1

7. Midbrain Ventral surface Crus cerebri (1)
Interpeduncular fossa (2) oculomotor nerves emerge from medial of crus cerebri
Posterior perforated substance (3)
Oculomotor nerve 2 1
III 3 VI

8. Midbrain Dorsal surface4 3
Dorsal surface
Superior colliculus (1) constitute centers for visual reflexes
Inferior colliculus (2) associated with auditory pathway
Brachium of superior colliculi
Brachium of inferior colliculi
Trochlear nerve (IV)
Medial geniculate body (3)
Lateral geniculate body (4) 1 2 IV

9. Fourth ventricle Position
Central canal →fourth ventricle →mesencephalic aqueduct→third ventricle
Position
Situated ventral to cerebellum, and dorsal to pons and cranial half of medulla

10. Fourth ventricle Boundaries
Inferolateral: gracile and cuneate tubercles, inferior cerebellar peduncle
Superolateral: superior cerebellar peduncle
Lateral recess

11. Fourth ventricle Floor Upper part:
Upper pontine and lower medullary separated by Striae medullares (1)
Median sulcus divided it into right and left halves (2 Medial eminences) (2)
Upper part:
Facial colliculus (3): overlies nucleus of abducent n. and fibers of facial nerve
Upper Vestibular area (4): overlies vestibular nuclei
Superior fovea (5) 2 5 4
Sulcus Limitans 1 3

12. Fourth ventricle Lower part:
Hypoglossal triangle (1): overlying hypoglossal nucleus
Lower Vestibular area (2)
Vagal triangle (3): overlies dorsal nucleus of vagus nerve
Inferior Fovea ( Inverted Y ). 2 2 2 1 3

13. Fourth ventricle
Roof
Upper part: formed by superior cerebellar peduncle and superior medullary velum
Lower part: formed by inferior medullary velum and choroid plexus of fourth ventricle
Three apertures
Median aperture of fourth ventricle
Two lateral apertures of fourth ventricle

14. Internal structures
Gray matter
Cranial nerve nuclei
Relay nuclei

15. Names of cranial nerves
Ⅰ Olfactory nerve
Ⅱ Optic nerve
Ⅲ Oculomotor nerve
Ⅳ Trochlear nerve
Ⅴ Trigeminal nerve
Ⅵ Abducent nerve
Ⅶ Facial nerve
Ⅷ Vestibulocochlear nerve
Ⅸ Glossopharyngeal nerve
Ⅹ Vagus nerve
Ⅺ Accessory nerve
Ⅻ Hypoglossal nerve

16. Functional components
General somatic afferent fibers (GSA): transmit exteroceptive and proprioceptive impulses from head and face to somatic sensory nuclei
Special somatic afferent fibers (SSA): transmit sensory impulses from special sense organs of vision, equilibrium and hearing to the brain
General visceral afferent fibers (GVA): transmit interoceptive impulses from the viscera to the visceral sensory nuclei
Special visceral afferent fibers (SVA): transmit sensory impulses from special sense organs of smell and taste to the brain
General somatic efferent fibers (GSE): innervate skeletal muscles of eye and tongue
Special visceral efferent fibers (SVE): transmit motor impulses from the brain to skeletal muscles derived from brachial (gill) arches of embryo. These include the muscles of mastication, facial expression and swallowing
General visceral efferent fibers (GVE): transmit motor impulses from the general visceral motor nuclei and relayed in parasympathetic ganglions. The postganglionic fibers supply cardiac muscles，smooth muscles and glands

17. Classification of cranial nerves
Sensory cranial nerves: contain only afferent (sensory) fibers
ⅠOlfactory nerve
ⅡOptic nerve
Ⅷ Vestibulocochlear nerve
Motor cranial nerves: contain only efferent (motor) fibers
Ⅲ Oculomotor nerve
Ⅳ Trochlear nerve
ⅥAbducent nerve
Ⅺ Accessory nerv
Ⅻ Hypoglossal nerve
Mixed nerves: contain both sensory and motor fibers---
ⅤTrigeminal nerve,
Ⅶ Facial nerve,
ⅨGlossopharyngeal nerve
ⅩVagus nerve

18. Sensory cranial nerves
Location of cell body and axon categories
Cranial exit
Terminal nuclei
Main action Ⅰ
Olfactory cells (SVA)
Cribrifom
foramina
Olfactory bulb
Smell Ⅱ
Ganglion cells (SSA)
Optic canal
Lateral geniculate body
Vision Ⅷ
Vestibular ganglion(SSA)
Internal acoustic meatus
Vestibular nuclei
Equilibrium
Cochlear ganglion (SSA)
Cochlear nuclei
Hearing

19. Motor cranial nerves N. Nucleus of origin and axon categories
Cranial exit
Main action Ⅲ
Nucleus of oculomotor (GSE)
Superior orbital fissure
Motor to superior, inferior and medial recti; inferior oblique; levator palpebrae superioris
Accessory nucleus of oculomotor (GVE)
Parasympathetic to sphincter pupillea and ciliary muscles Ⅳ
Nucleus of trochlear nerve (GSE)
Motor to superior oblique Ⅵ
Nucleus of abducent nerve (GSE)
Motor to lateral rectus Ⅺ
Nucleus of accessory nerve (SVE)
Jugular foramen
Motor to sternocleidomastoid and trapezius Ⅻ
Nucleus of hypoglossal nerve( GSE)
Hypoglossal canal
Motor to muscles of tongue except palatoglossus

20. General somatic efferent nuclei
Nucleus of oculomotor n.
Nucleus of trochlear n.
Nucleus of abducent n.
Nucleus of hypoglossal n.

21. Special visceral motor nuclei
Motor nucleus of trigeminal n.
Nucleus of facial n.
Nucleus ambiguous
Accessory nucleus

22. Special visceral efferent nuclei
Nucleus
Site
Cranial n.
Function
Motor nucleus of trigeminal n.
Pons Ⅴ
Masticatory muscles, tensor palati & t. tympani
Nucleus of facial n. Ⅶ
Facial m., platysma, posterior belly of digastric, stylohyoid, stapedius
Nucleus ambiguus
Medulla
Ⅸ,Ⅹ.Ⅺ
Skeletal m. of pharynx, larynx and upper part of esophagus
Accessory nucleus
Medulla-cervical cord Ⅺ
Sternocleidomastoid, trapezius

23. General visceral motor nuclei
Accessory oculomotor nucleus
Superior salivatory nucleus
Inferior salivertory nucleus
Dorsal nucleus of vagus n.

24. Visceral sensory nuclei ( general and special )
Nucleus of solitary tract

25. Visceral sensory nuclei ( general and special )
Nucleus
Site
Cranial n.
Function
Nucleus of solitary tract
Medulla
Ⅶ,Ⅸ,Ⅹ
Taste and visceral sensation

26. General somatic afferent nuclei
Mesencephalic nucleus of trigeminal n.
Main sensory nucleus of trigeminal n.
Spinal nucleus of trigeminal n.

27. General somatic sensory nuclei
Nucleus
Site
Cranial n.
Function
Mesencephalic nucleus of trigeminal n.
Midbrain Ⅴ
Proprioception of head
Main sensory nucleus of trigeminal n.
Pons
Tactile sensation of face
Spinal nucleus of trigeminal n.
Medulla upto 2nd cx. seg.
Pain and temperature sense of face

28. Special somatic afferent nuclei
Cochlear nuclei 2
- Dorsal
- Ventral
Vestibular nuclei 4
- Superior
- Inferior
- Medial
- Lateral

29. Special somatic afferent nuclei
Nucleus
Site
Cranial n.
Function
Cochlear nuclei
Pons and medulla Ⅷ
Sense of hearing
Vestibular nuclei
Sense of equilibrium

30. Non-cranial nerve nuclei
Nucleus
Site
Gracile nucleus
Medulla (underneath gracile tubercle)
Cuneate nucleus
Medulla (underneath cuneate tubercle)
Superior olivery nucleus
Pons
Pontine nucleus
pons
Nucleus of inferior colliculus
Midbrain
Gray matter layers of superior colliculus
Red nucleus
Substantia nigra
Pretectal area