brain division

telencephalon Brain diencephalon cerebellum midbrain brain stem pons mudulla

oblongata

BRAIN DIVISION

1.Location ： Being in the skull , it superiorly connects diencephalon , inferiorly conjoins spinal cord

and ventrally lies on the clivus of occiptal bone and posteriorly attaches cerebellum.

I.Brain Stem

2.External Borders (1) ventral surface a. bulbopotine sulcus b. sup border of basilar part in pons (2) dorsal surface a. striae medullares b. lower border of inf colliculi

3. Parts and Ventral Appearances

Cerebral

peduncles

Interpeduncular fossa

Basilar part of ponsBasilar sulcus

PyramidsDecussation of pyramidInferior olives

Midbrain

Pons

Medulla oblongata

Superior colliculiBrachiums of superior colliculiInferior colliculiBrachiums of inferior colliculi

4. Parts & Dorsal Appearances(A)

mid

brai

n

Paired Structures

median sulcus 1sulcus limitensredullary stria 1 medial eminencesfacial colliculivagal-triangles hypoglossal trianglesvestibular areassup, mid & inf cerebellar peducles

Pon

s & M

edu

lla O

blon

gata

Parts & Dorsal Appearances(B)

pai

Paired structures

Rhomboid Fossa(4th ventricle floor)

3) Names of Cranial Nerve(CN)

I olfactory nII optic n

Ⅲ oculomotor n Ⅳ trochlear n Ⅴ trigeminal n Ⅵ abducent n (dorsal

origin) Ⅶ facial n

Ⅷ vestibulocochlear n

Ⅸ glossopharyngeal n

Ⅹ vagus n

Ⅺ accessory n Ⅻ hypoglossal n

Pons

Medullaoblongata

Ⅲ oculomotor n Ⅳ trochlear n

Ⅴ trigeminal n

Ⅵ abducent n

Ⅶ facial n Ⅷ vestibulo- cochlear n

Ⅸ glosso- pharyngeal n Ⅹ vagus n

Ⅺ accessory n

Ⅻ hypoglossal n

Midbrain

Connections with Parts

3.Internal Structure Inclusion: gray matter,white matter &

reticular formation Characteristics of Gray Matter :

Think about the followimg questions:1.What nuclei exist in midbrain,pons and medulla oblongta, respectively?2.Which are cranial nuclei or non-cranial nuclei? 3.How many kinds of cranial nuclei in brain stem? somatic motor nuclei visceral motor nuclei visceral afferent nuclei somatic afferent nuclei

Division of

Brain Stem

Somatic Motor Nuclei Lying Immediately Lateral to Median Sulcus

midbrain

pons

medulla oblongata

nucleus of trochlear n

nucleus of abducent n

nucleus of hypoglossal n

nucleus of oculomotor n

Localization of Somatic Motor Nuclei

Nucleus of trochlear n

Nucleus of abducent n

Nucleus of hypoglossal n

Nucleus of oculomotor n Top-bottom

arrangement

Dorsal surface of brain stem

Division of

Brain Stem

General Visceral Motor Nuclei of CN Immediately Medial to Sulcus Limitans

midbrain

pons

medulla

oblongata

accessory nucleus of oculomotor n

superior salivary nucleus

inferior salivary nucleus

dorsal nucleus of vagus n

Localization of General Visceral Motor Nuclei

Accessory nucleus of oculomotor n

Superior salivary n

Inferior salivary n

Dorsal nucleus of vagus n

motor nucleus of trigeminal n

nucleus of facial n

ambiguous nucleus

accessory nucleus

Division of

Brain Stem

Special Visceral Motor Nuclei of CN Ventrolateral to VMN & Medial to Sulcus Limitans

midbrain

pons

medulla

oblongata

Localization of Special Visceral Motor Nuclei

Motor nucleus

of trigeminal n

Nucleus of facial n

Ambiguous nucleus

Accessory nucleus

Division of

Brain Stem General & Special Visceral Sensory Nucleus of CN Immediatedly Lateral to Sulcus Limitans

midbrain

pons

medulla

oblongata nucleus of solitary tract

Localization of General & Special Visceral Sensory Nucleus

none

none

Nucleus of

solitary tract

Division of Brain Stem

General & Special Somatic Sensory Nuclei Lateral & Dorsalolateral to GSVSN

midbrain

pons

medulla oblongata

mesencephalic nucleus of trigeminal n

cochlear nuclei

vestibular nuclei

pontine nucleus of trigeminal n

spinal nucleus of trigeminal n

Localization of General & Special Somatic Sensory Nuclei

Mesencephalic nucleus of trigeminal n

Cochlear & vestibular nuclei

pontine nucleus of trigeminal n

Spinal nucleus of trigeminal n

Division of Brain Stem

midbrain

nucleus of sup. colliculus

black substance

pontine nucleus

gracile nucleus cuneate nucleus

pons

medulla oblongata

Nuclei of Non-Cranial Nerves

nucleus of inf. colliculus

red nucleus

Localization of Non-Crainal Nuclei

1.Discern which one is a cranial nucleus, ambiguous or gracile nucleus ？

2. Distinguish the category of the following nuclei:

black substancered nucleus cochlear

nuclei

vestibular nuclei

accessory nucleus

dorsal nucleus of vagus nnucleus of hypoglossal n

Test Yourself

3.How many nuclei are there in medullar oblongata ?

4.Which nucleus is in pons?

( memorize nuclei according to their positions ）

Black substance

Red nucleus Cochlear nuclei

Vestibular nucleiAccessory nucleus

Dorsal nucleus of vagus N.

Nucleus of hypoglossal N.

5.Which one is somatic nucleus? (to memorize four kinds of cranial N respectively according to their functions)

Nucleus of oculomotor N

Accessory nucleus of oculomotor N

Spinal nucleus of trigeminal N.

Nucleus of solitary tract

Nucleus of facial N

6.Four pairs of parasympathetic nuclei exsit in brain stem:

accessory nucleus of oculomotor n

superior salivary nucleus

inferior salivary nucleus

dorsal nucleus of vagus n

7.Relationships between nuclei & cranial nerves

1) one nucleus connects 1 nerve 2) one nucleus connects 2 or more nerves nucleus of solitary tract Ⅶ、

Ⅸ 、

Ⅹ ambiguous nuleus Ⅸ、

Ⅹ 、

Ⅺ

3) Two or more nuclei connect one nerve:

a. oculomotor nu, accessory nu of oculomotor n---Ⅲ

b. sensory & motor nus of trigeminal n---------------Ⅴ

c. facial nu, sup. salivary nu, solitary tract nu------Ⅶ

d. ambiguous , inf.salivary,solitary tract nus------Ⅸ

e. ambiguous nu, dorsal nu of vagus n, solitary tract nu, spinal nu of trigeminal n------------- - Ⅹ

Cranial N and Relative Nuclei

III

V

VIVIII

XI

IX

X

XII

IV

VII

White Matter of Brain Stem

Ascending tracts ：1.medial lemniscus2.spinal lemniscus3.trigeminal lemniscus4.lateral lemniscus

Descending tracts:1.corticospinal tract2.corticonucleus tract3.extrapyramid tract

Overview of Microstructures of White Matter

1. White matter consists of numerous nerve fibers.

2. The certain bundle fibers with the same origin,

course,end & functions form a tract.

3. The fiber tracts of brain include both ascending

& descending ones(ascending –blue;descending –red).4. Focus on the names (according to origin & end )

formations ( Which nucleus receives or sends the

bundled fibers ? ), locations ( Where do the fibers

pass via the brain stem ? ) and functions ( What

information do the fibers transmit ? ) of the main

tracts. Descending Tract

1.Medial Lemniscus

medial lemniscus

↑

decussation of

med lemniscus

↑

gracile nucleus

cuneate nucleus

↑

fasciculus gracilis

fasciculus cuneatus

2.Spinal Lemniscus

anterior spinal lemniscus

lateral spinal lemniscus

3.Trigeminal Lemniscus

trigeminal lemniscus

↑

decussation of trigeminal lemniscus

↑

pontine nucleus & spinal nucleus of trigeminal n

4.Lateral Lemniscus

lateral lemniscus

↑

↑ uncrossed

↑ crossed

trapezoid body

↑

cochlear nuclei

Descending Tract 1. Pyramidal Tract 1) corticonuclear tract 2) corticospinal tract

2. Extrapyramidal System

1) Corticonuclear Tract a.inf.part of precentral gyrus ↓ motor nuclei in brain stem

b.The tract dominates the most nuclei on both sides of brain stem. c.Lower-half parts of facial nu & hypoglossal nu only receive the control of the tract from opposite side. d.The tract controls voluntarily

muscular movements of head, face and neck .

2) Corticospinal Tract

c.The tract controls movements of voluntary muscles in trunk and limbs.

superior & middle part of precentral gyrus

↓

ant horn cells of spinal cord

a.Most fibers decussate at decussation of pyramid.

b.Fewer fibers decussate at ant white commissure.

All the descending tracts except pyramidal tracts dominating the vuluntarily muscular movements, are subordinated to the system. The functions of the system are to modulate the voluntarily muscular movements. The conbination of the two system enables the body to carry out the appropriate, precise , effective, harmonious & temporospatial

movements so as to reliably respond to the stimuli from external or internal enviroments.

Extrapyramidal System

Reticular Formation of Brain Stem

Raphe nuclei locates in median line of brain stem.

Functions ：1) ascending : helping sleep2) descending: alleviating pain

Ascending Reticular Activating System--ARAS

Location ：

dorsolateral area of pons and medullar oblongata

Functions:(1)~(3)

Fiber projection

targets of ARAS

(1)Receives the informations transmitted by the numerous lateral branches given off by the responding specific sensation conduction tracts. (2)converts these specific messages into non-specific ones ,and then sends them to most areas of cortex of cerebrum via its projection fibers. (3) thus makes the cortex be conscious or vigilant states so as to be able to recognize and distinguish the various afferent messages.

Lateral branches

Sensory pathwayspons

bolb

Fibers to cortex

Functions of Reticular Formation a.Regulating somatic movements: strengthen or weaken muscular tensions . b.Performing the behavioral arousal function. c.Controlling the activities: vomiting center;regulating visceral reflexes(DS&RS); centers for vital movements , including cardiovascular motor center & respiratory center----controlling heartbeat, BP& R. d.5-TH ascending projection to cerebral cortex inhibits activities of the cortex and induces human to sleep.5-TH descending projection to the spinal cord plays roles in modulating cardiovascular activities and pain sensation.

Relationship between External Appearance & Internal Structure

1.Dorsal Surfacesup colliculus---—-------------------- ----its nulceus inf colliculus--------------------------------its nucleus vestibular area-------------------vestibular nucleus facial colliculus------------------abducens nucleus

hypoglossal triangle-----------------------its nucleus vagal triangle-----------------dorsal nucleus of X n

acoustic tubercle----------------dorsal nuclei of VIII nlocus ceruleus-----------------------------its nucleus gracile tubercle----------------------------its nucleus cuneate tubercle---—---------------------its nucleus

aera postrema---chemical receptor –activative vomiting center; the relay stops ofviceral information exchange & visceral reflexes;an area controlling neuroendocrine secretion.

obex---

Relationship between External Appearance & Internal Structure

2.Ventral Surface

pyramid-corticospinal tract

pyramidal decussation--lateral corticospinal tract(ventral crossding;decussation of medial lemniscus-dorsal crossing,,both approximately at the same level in oblongata)

olive---inferior olivary nucleus

pontine base—pontine nucleus

Cerebellum

Location:

lying in posterior cranial fossa & attachingdorsum of brain stem

External Features 2 parts ,1 tonsil& significance

cerebellar hemisphere

vermis

tonsil of cerebellum

If intracranial pressure

sharply increases ,the tonsil

will be pressed toward

oblongata (tonsillar hernia),

leading to sudden death.

Lobes and Their FunctionsFlocculonodular lobe-----keeps the balances of bodyAnterior lobe-----regulates muscular tension. Posterior lobe-----coordinates the movements of voluntary muscles

Internal Structures of Cerebelluncortex ： three layers . sends fibers to central nucleimedulla ： central nuclei of cerebellum(four pairs )

Dentate N

emoliformGlobse N

Fastigial N

Fiber Connections of the Cerebellum

1. Three pairs of

cerebellar peduncles:

superior, middle,inferior

2. Fiber connection circuit:

Primary afferent fibers from

other parts in CNS first enter

the cortex of cerebellum (Piriform cells /Purkinjie cells which are the only efferent neurons in the cortex receive the afferents and then send their own fibers to central nuclei in medulla, and finally the central nuclei send their efferent fibers from medulla of cerebellum to other parts in CNS.Complete the transmission !

Infer.cereb. ped

Mid. cereb. ped

Sup.cereb. ped

Vestibular N

Vestibular ganhlion

Cortex of cerebellum

Vestibulospinal tract