cerebellum ( 小脑 ) the cerebellum is the second-largest portion of the brain and occupies the...

Cerebellum

( 小脑 )

The cerebellum is the second-largest portion of the brain and occupies the inferior and posterior aspects of the cranial cavity. It is posterior to medulla oblongata and pons, and is

inferior to the occipital

lobes of the cerebrum. It

is separated from the

cerebrum by the

transverse fissure.

transverse fissure

of cerebrum

midbrain

occipital lobe of cerebrum

The fourth ventricle

Mesencephalic aqueduct

pons

Medulla oblongata

cerebellum

cerebellum

midbrain

pons

Medulla oblongata

cerebellum

cerebellu

m

Hypophysis

Dorsal thalamus

The fourth ventricle


ponsMedulla

oblongata

hypothalamus

背侧丘脑

小脑延髓

下丘脑

脑桥脑垂体

第四脑室

中脑水管

The cerebellum is shaped somewhat like a butterfly. The central constricted area is called cerebellar vermis( 小脑蚓部 ), and the lateral parts are referred to as cerebellar hemispheres( 小脑半球 ).

cerebellar vermisAnterior

lobe

posterior lobe

Primary

fissure

Horizontal fissure

Cerebellar hemisphereInferior semilunar lobule

superior semilunar lobule

小脑上面

原裂

中央小叶山顶

山坡

水平裂

方形小叶前部

方形小叶后部

上半月小叶

下半月小叶

Ⅰ. The lobes of Cerebellum

The cerebellum can be divided by its connections and phylogeny into three portions:

1. The flocculonodular lobe ( 绒球小结叶 )

This lobe includes flocculus, nodule and crus of flocculus, and is predominantly vestibular in its connections.

The flocculonodular lobe constitutes the oldest part of cerebellum, so it is called the vestibulocerebellum ( 前庭小脑 ) or archicerebellum ( 古 / 原小脑 ).

vermis

nodule

flocculus

cerebellar tonsil

Superior cerebellar peduncle

uvulaBiventral lobule

Crus of flocculus

middle cerebellar peduncle

小脑下面

中央小叶小脑上脚

小脑中脚

小脑下脚

小脑扁桃体

绒球绒球脚

小节

蚓锥体下半叶小叶

二腹小叶

2. The anterior lobe and the rostral part of inferior verm

is

The anterior lobe, uvula and pyramid of vermis are predominantly spinocerebellar

in its connections and is phylogenetically the next part to appear, it is also called the spinocerebellum( 脊髓小脑 ) or paleocerebellum ( 旧小脑 ).

vermisAnterior lobe

posterior lobe

Primary

fissure

Horizontal fissure


Inferior semilunar lobule

小脑上面

原裂

中央小叶山顶

山坡

水平裂

方形小叶前部

方形小叶后部

上半月小叶

下半月小叶

vermis

cerebellar tonsil

uvula of vermis

Pyramid of vermis

Biventral lobule

Inferior semilunar lo

bule

vermis

nodule

flocculus

cerebellar tonsil


uvula of vermisPyramid of vermis

Biventral lobule


小脑下面

中央小叶小脑上脚

小脑中脚

小脑下脚

小脑扁桃体

绒球绒球脚

小节

蚓锥体下半月小叶

二腹小叶

3. The posterior lobe

This lobe is the largest one and include the portions of cerebellar hemispheres posterior to the primary fissure. It is predominantly

corticopontocerebellar in its connections and constitutes the cerebrocerebellum( 大脑小脑 ) or neocerebellum ( 新小脑 ).

vermisAnterior lobe

posterior lobe

Primary

fissure

Horizontal fissure


superior semilunar lobule

vermis

nodule

flocculus

cerebellar tonsil


uvulaPyramid of vermis

Biventral lobule


Ⅱ. The cerebellar cortex

The cerebellar cortex is uniformly structured in all parts and consists of three layers. From exterior to interior, they are: molecular layer, Purkinje cell layer and granular layer.

molecular layer

Purkinje cell

layergranular layer

Purkinje cell

Mossy fibers

climbing fibersAxon of Purkinje

cell

Basket cell

Golgi cell

granular cell

There are two types of afferent fibers to the cercerebellar cortex: Mossy fibers( 苔藓纤维 ) and climbing fibers ( 攀缘纤维 ).

Mossy fibers terminate in synaptic contact with cells of the granular layer, through which they affect the Purkinje Cells.

The climbing fibers enter the molecular layer and wind around the dendrites of Purkinje cells. The only fibers leaving the cerebellar cortex are axons of Purkinje cells, which terminate in central

nuclei of the cerebellum with the exception of some fibers from the cortex of the flocculonodular lobe (they enter the brain stem).

Ⅲ. The central nuclei of cerebellum

There are four pairs of nuclei in the medullary center: the fastigial nuclei( 顶核 ), globose nuclei ( 球状核 ), emboliform and dentate nuclei ( 齿状核 ).

Fastigial nucleus

Globose nucleus

Emboliform nucleus

Dendate nucleus

Cerebellar cortex

Cerebellar medullary subatance

The fastigial nucleus receives the fibers from the archicerebellum. Most fibers from this nucleus end in the vestibular nuclei of both sides and the reticular formation of medulla oblongata by inferior cerebellar peduncle.

The dentate nucleus receives fibers from cerebellar cortex. The efferent fibers of it end in the red nucleus and the thalamus of contralateral side by the superior cerebellar peduncle.

Ⅳ. The cerebellar peduncles

1. The inferior cerebellar peduncle (restiform body/ 绳状体 )

cerebellar tonsil


Dendate nucleus


inferior cerebellar peduncle

Medulla oblongata

Lateral lemniscus

The inferior cerebellar peduncle is composed of olivocerebellar tract, posterior spinocerebllar tract and the fibers from reticular formation of medulla oblongata, vestibular nuclei and vestibular nerve.

It also contains the efferent fibers which arise from the flocculonodular lobe and fastigial nucleus to the vestibular nuclei and the reticular formation of medulla oblongata and pons.

2. The middle cerebellar peduncle (brachium pontis/脑桥臂 )

It is almost composed of the pontocerebellar fibers .

3. The superior cerebellar peduncle (brachium conjunc

tivum/ 结合臂 )

It connects the cerebellum with the midbrain and thalamus and consists mainly

of the efferent fibers from the globose, emboliform and dentate nuclei. It also contains afferent fibers, such as the anterior spinocerebellar tract.

Superior cerebellar p

eduncle

Dendate nucleus

Trigeminal nerve

vermis


Inferior colliculus Mesencephalic aqueduct


Dendate nucleus

Trigeminal nerve

vermis


Inferior colliculus


Dendate nucleus

Ⅴ. Functions of cerebellum

1.coordinates the movements of skeletal muscles in the body;

2.maintains the equilibrium and controls the posture of the body;

3. Modulates the muscle

tone(the tonicity of

muscles );

4.predicts the future

posture of a body part in

the movements.

cerebellum ( 小脑 ) the cerebellum is the second-largest portion of the brain and occupies the...

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