BRAIN
DIVISION
telencephalon
Brain diencephalon
cerebellum midbrain
brain stem pons
mudulla
oblongata
I.Brain Stem
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.
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
Midbrain
peduncles
Interpeduncular
fossa
Pons
Medulla
oblongata
Basilar part of
pons
Basilar sulcus
Pyramids
Decussation
of pyramid
Inferior olives
4. Parts & Dorsal
Appearances(A)
midbrain
Superior
colliculi
Brachiums
of superior
colliculi
Inferior
colliculi
Brachiums
of inferior
colliculi
Paired Structures
Rhomboid Fossa Parts & Dorsal Appearances(B)
(4th ventricle floor)
Pons & Medulla Oblongata
median sulcus 1
sulcus limitens
redullary stria 1
medial eminences
facial colliculi
vagal-triangles
hypoglossal
triangles
vestibular areas
sup, mid & inf
cerebellar peducles
Paired structures
p
3) Names of
Cranial Nerve(CN)
I olfactory n
II 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
Connections with Parts
Ⅲ oculomotor n
Midbrain
Ⅳ trochlear n
Ⅴ trigeminal n
Ⅵ abducent n
Ⅶ facial n
Ⅷ vestibulocochlear n
Ⅸ glossopharyngeal n
Medulla Ⅹ vagus n
oblongata
Ⅺ accessory n
Pons
Ⅻ hypoglossal n
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
Localization of Somatic Motor Nuclei
Division of
Brain Stem
Somatic Motor Nuclei Lying Immediately
Lateral to Median Sulcus
midbrain
nucleus of oculomotor n
nucleus of trochlear n
pons
nucleus of abducent n
medulla
oblongata
nucleus of hypoglossal n
Top-bottom
arrangement
Nucleus of
oculomotor n
Nucleus of
trochlear n
Nucleus of
abducent n
Dorsal surface
of brain stem
Nucleus of
hypoglossal n
Localization of General Visceral Motor Nuclei
Division of
Brain Stem
General Visceral Motor Nuclei of CN
Immediately Medial to Sulcus Limitans
midbrain accessory nucleus of oculomotor n
pons
superior salivary nucleus
medulla
inferior salivary nucleus
dorsal nucleus of vagus n
oblongata
Accessory nucleus
of oculomotor n
Superior salivary n
Inferior salivary n
Dorsal
nucleus of
vagus n
Localization of Special Visceral Motor Nuclei
Brain Stem
Special Visceral Motor Nuclei of CN
Ventrolateral to VMN &
Medial to Sulcus Limitans
midbrain
motor nucleus of trigeminal n
Division of
pons
nucleus of facial n
medulla
ambiguous nucleus
oblongata
accessory nucleus
Motor nucleus
of trigeminal n
Nucleus of facial n
Ambiguous nucleus
Accessory nucleus
Localization of General & Special
Visceral Sensory Nucleus
Division of
Brain Stem
General & Special Visceral Sensory Nucleus
of CN Immediatedly Lateral to Sulcus Limitans
midbrain
none
pons
none
medulla
oblongata
nucleus of solitary tract
Nucleus of
solitary tract
Localization of General & Special Somatic Sensory Nuclei
Division of
Brain Stem
General & Special Somatic Sensory
Nuclei Lateral & Dorsalolateral to GSVSN
mesencephalic nucleus
of trigeminal n
midbrain
pons
cochlear
nuclei
vestibular
nuclei
medulla
oblongata
pontine nucleus
of trigeminal n
spinal nucleus of
trigeminal n
Mesencephalic nucleus
of trigeminal n
pontine nucleus
of trigeminal n
Cochlear &
vestibular
nuclei
Spinal nucleus of
trigeminal n
Localization of Non-Crainal Nuclei
Division of
Nuclei
of
Non-Cranial
Nerves
Brain Stem
midbrain
nucleus of sup. colliculus
nucleus of inf. colliculus
red nucleus
black substance
pons
pontine nucleus
medulla
oblongata
gracile nucleus
cuneate nucleus
Test Yourself
1.Discern which one is a cranial nucleus,
ambiguous or gracile nucleus ？
2. Distinguish the category of the following nuclei:
red nucleus
black substance
accessory nucleus
cochlear
nuclei
dorsal nucleus of vagus n
nucleus of hypoglossal n
vestibular
nuclei
3.How many nuclei are there in medullar
oblongata ?
4.Which nucleus is in pons?
( memorize nuclei according to their positions）
Red nucleus
Black substance
Accessory nucleus
Cochlear
nuclei
Vestibular
nuclei
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
Nucleus of facial N
Accessory nucleus of oculomotor N
Nucleus of solitary tract
Spinal nucleus of trigeminal 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
Ⅸ、
ambiguous nuleus
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
III
IV
V
VIII
VI
VII
XII
XI
IX
X
Cranial N and Relative Nuclei
White Matter of Brain Stem
Ascending tracts：
1.medial lemniscus
2.spinal lemniscus
3.trigeminal lemniscus
4.lateral lemniscus
Descending tracts:
1.corticospinal tract
2.corticonucleus tract
3.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
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.
c.The tract controls
movements of voluntary
muscles in trunk and limbs.
Extrapyramidal System
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.
Reticular
Formation of
Brain Stem
Raphe nuclei
locates in
median line
of brain stem.
Functions：
1) ascending :
helping sleep
2) descending:
alleviating pain
Ascending
Reticular
Activating
System--ARAS
Location：
dorsolateral
area of pons
and medullar
oblongata
Functions:
(1)~(3)
(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.
Fiber
projection
targets of
ARAS
Fibers to cortex
Lateral branches
pons
bolb
Sensory pathways
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 Surface
sup 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 n
locus ceruleus-----------------------------its nucleus
gracile tubercle----------------------------its nucleus
cuneate tubercle---—---------------------its nucleus
aera postrema---chemical receptor –activative vomiting center; the relay stops of
viceral 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
& attaching
dorsum 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 Functions
Flocculonodular lobe-----keeps the balances of body
Anterior lobe-----regulates muscular tension.
Posterior lobe-----coordinates the movements of
voluntary muscles
Internal Structures of Cerebellun
cortex：three layers . sends fibers to central nuclei
medulla：central nuclei of cerebellum(four pairs )
Fastigial N
Globse N
emoliform
Dentate 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
Sup.cereb. ped
cells which are the only
efferent neurons in the
Mid. cereb. ped
cortex receive the afferents
and then send their own fibers
Infer.cereb. ped
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 !
Vestibular N
Cortex of
cerebellum
Vestibular
ganhlion
Vestibulospinal tract