Brain stem & Cerebellum

The brain

Telencephalon Diencephalon Cerebellum Brain stem

The brain stem

Consists of Midbrain Pons Medulla oblongata

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2

3

Medulla oblongataVentral surface Pyramid: contain pyramidal tr

act (corticospinal tract) Decussation of pyramid: form

ed 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

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2

3

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XIIIX

XXI

Medulla oblongata

Dorsal surface Lower portion

Gracile tubercle: produced by und

erlying gracile nucleus Cuneate tubercle: marks the site

of cuneate nucleus Inferior cerebellar peduncle Obex

Upper portion: forms the lower half of rhomboid fossa

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3

45

Pons

Ventral surface Basilar part Basilar sulcus Bulbopontine sulcus: from m

edial to lateral, the abducent, facial and vestibulocochlear nerves appear

Middle cerebellar peduncle Trigeminal nerve Pontocerebellar trigone: the j

unction of medulla, pons and cerebellum

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2

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5VVI

VIIVIII

Pons

Dorsal surface Superior cerebellar pedu

ncle Superior medullary velu

m Trochlear nerve

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32

Midbrain

Ventral surface Crus cerebri Interpeduncular fossa o

culomotor nerves emerge from medial of crus cerebri

Posterior perforated substance

123III

VI

Midbrain

Dorsal surface Superior colliculus con

stitute centers for visual reflexes

Inferior colliculus associated with auditory pathway

Brachium of superior colliculi

Brachium of inferior colliculi

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2

34

IV

Fourth ventricle

Position Situated ventral to

cerebellum, and dorsal to pons and cranial half of medulla

Central canal →fourth ventricle →mesencephalic aqueduct→third ventricle

Boundaries Inferolateral: gracile an

d cuneate tubercles, inferior cerebellar peduncle

Superolateral: superior cerebellar peduncle

Lateral recess

Features Median sulcus Sulcus limitans Vestibular area overlies vestib

ular nuclei

Acoustic tubercle overlying dorsal cochlear nucleus

Medial eminence Striae medullares

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2

3

5

6 4

Facial colliculus: overlies nucleus of abducent n. and genu of facial nerve

Hypoglossal triangle: verlyi

ng hypoglossal nucleus Vagal triangle: overlies dorsal

nucleus of vagus nerve

Inferior Fovea

Area postrema

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22235

44 4

Roof Anterior part: formed by s

uperior cerebellar peduncle and superior medullary velum

Posterior part: formed by inferior medullary velum and choroid plexus of fourth ventricle

Three apertures Median aperture of fourth

ventricle Two lateral apertures of fo

urth ventricle

Internal structures

Gray matter Cranial nerve nuclei Relay nuclei

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

Functional components General somatic afferent fibers (GSA): transmit exteroceptive an

d 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

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

Sensory cranial nervesN. Location of cell

body and axon categories

Cranial exit

Terminal nuclei

Main action

Ⅰ Olfactory cells (SVA)

Cribrifomforamina

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

Motor cranial nervesN. Nucleus of origin and

axon categoriesCranial 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)

Superior orbital fissure

Motor to superior oblique

Ⅵ Nucleus of abducent nerve (GSE)

Superior orbital fissure

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

General somatic efferent nuclei

Nucleus of oculomotor n.

Nucleus of trochlear n.

Nucleus of abducent n.

Nucleus of hypoglossal n.

Special visceral motor nuclei

Motor nucleus of trigeminal n.

Nucleus of facial n.

Nucleus ambiguous

Accessory nucleus

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. Pons 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

General visceral motor nuclei

Accessory oculomotor nucleus

Superior salivatory nucleus

Inferior salivertory nucleus

Dorsal nucleus of vagus n.

General visceral efferent nucleiNucleus Site Cranial

nerveFunction

Accessory oculomotor nucleus

Midbrain Ⅲ Sphincter pupillae and ciliary m.

Superior salivatory nucleus

Pons Ⅶ Submandibular, sublingual and lacrimal glands

Inferior salivertory nucleus

Medulla Ⅸ Parotid gland

Dorsal nucleus of vagus n.

medulla Ⅹ Many cervical, thoracic and abdominal viscera

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

Visceral sensory nuclei ( general and special )

Nucleus Site Cranial n. Function

Nucleus of solitary tract

Medulla Ⅶ, ,Ⅸ Ⅹ Taste and visceral sensation

General somatic afferent nuclei Mesencephalic nucleu

s of trigeminal n.

Main sensory nucleus of trigeminal n.

Spinal nucleus of trige

minal n.

General somatic sensory nucleiNucleus Site Cranial

n.Function

Mesencephalic nucleus of trigeminal n.

Midbrain Ⅴ Proprioception of head

Main sensory nucleus of trigeminal n.

Pons Ⅴ Tactile sensation of face

Spinal nucleus of trigeminal n.

Medulla upto 2nd cx. seg.

Ⅴ Pain and temperature sense of face

Special somatic afferent nuclei Cochlear nuclei 2

- Dorsal

- Ventral Vestibular nuclei 4

- Superior

- Inferior

- Medial

- Lateral

Special somatic afferent nuclei

Nucleus Site Cranial n. Function

Cochlear nuclei

Pons and medulla

Ⅷ Sense of hearing

Vestibular nuclei

Pons and medulla

Ⅷ Sense of equilibrium

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

Midbrain

Red nucleus Midbrain

Substantia nigra Midbrain

Pretectal area Midbrain

Cerebellum

Site: Posterior cranial fossa, behind pons & medulla oblongata.

2 Surfaces: Superior & Inferior. 3 Parts:

* Vermis

- Superior: indistinct from sup. surface.

- Inferior: lodged in the vallecula.

* 2 Lobes

Cerebellum

3 Fissures:

* Primary

* Horizontal

* Posterolateral

Functional Divisions:

* Archi-cerebellum: vestibulo-cerebellum.

* Paleo-cerebellum: spino-cerebellum.

* Neo-cerebellum: ponto-cerebellum.

Cerebellum