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 inferior to the occipital lobes of the cerebrum. It is separated from the cerebrum by the transverse fissure.

occipital lobe of cerebrum midbrain Mesencephalic aqueduct pons The fourth ventricle cerebellum transverse fissure of cerebrum Medulla oblongata

midbrain pons cerebellum Medulla oblongata cerebellum

Dorsal thalamus hypothalamus Mesencephalic aqueduct Hypophysis pons Medulla oblongata The fourth ventricle cerebellum

背侧丘脑 下丘脑 中脑水管 脑垂体 脑桥 第四脑室 小脑 延髓

The cerebellum is shaped somewhat like a butterfly 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).

superior semilunar lobule cerebellar vermis Anterior lobe Primary fissure posterior lobe superior semilunar lobule Horizontal fissure Cerebellar hemisphere Inferior semilunar lobule

中央小叶 方形小叶前部 山顶 方形小叶后部 原裂 山坡 上半月小叶 水平裂 下半月小叶 小脑上面

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).

Superior cerebellar peduncle middle cerebellar peduncle vermis middle cerebellar peduncle Crus of flocculus flocculus nodule uvula cerebellar tonsil Biventral lobule

中央小叶 小脑上脚 绒球脚 小脑中脚 绒球 小脑下脚 小节 二腹小叶 小脑扁桃体 蚓锥体 下半叶小叶 小脑下面

2. The anterior lobe and the rostral part of inferior vermis 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).

vermis Anterior lobe Primary fissure posterior lobe Inferior semilunar lobule Horizontal fissure Cerebellar hemisphere Inferior semilunar lobule

中央小叶 方形小叶前部 山顶 方形小叶后部 原裂 山坡 上半月小叶 水平裂 下半月小叶 小脑上面

Inferior semilunar lobule uvula of vermis vermis Biventral lobule Inferior semilunar lobule cerebellar tonsil Pyramid of vermis

Inferior semilunar lobule Superior cerebellar peduncle vermis flocculus nodule Biventral lobule Inferior semilunar lobule cerebellar tonsil uvula of vermis Pyramid of vermis

中央小叶 小脑上脚 绒球脚 小脑中脚 绒球 小脑下脚 小节 二腹小叶 小脑扁桃体 蚓锥体 下半月小叶 小脑下面

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).

vermis Anterior lobe Primary fissure posterior lobe superior semilunar lobule Horizontal fissure Cerebellar hemisphere Inferior semilunar lobule

Superior cerebellar peduncle Inferior semilunar lobule vermis flocculus nodule Biventral lobule Inferior semilunar lobule cerebellar tonsil uvula Pyramid of vermis

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.

Golgi cell Purkinje cell Basket cell molecular layer granular cell Purkinje cell layer granular layer climbing fibers Axon of Purkinje cell Mossy fibers

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).

Cerebellar medullary subatance Fastigial nucleus Globose nucleus Emboliform nucleus Cerebellar cortex Cerebellar medullary subatance Dendate nucleus

The fastigial nucleus receives the fibers from the archicerebellum 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 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)

Superior cerebellar peduncle Lateral lemniscus Superior cerebellar peduncle middle cerebellar peduncle inferior cerebellar peduncle Dendate nucleus cerebellar tonsil Medulla oblongata

Lateral lemniscus Superior cerebellar peduncle middle cerebellar peduncle Dendate nucleus inferior cerebellar peduncle cerebellar tonsil Medulla oblongata

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

Mesencephalic aqueduct Inferior colliculus Mesencephalic aqueduct Trigeminal nerve middle cerebellar peduncle Superior cerebellar peduncle Dendate nucleus vermis

Mesencephalic aqueduct Trigeminal nerve middle cerebellar peduncle Inferior colliculus Superior cerebellar peduncle Dendate nucleus Dendate nucleus vermis

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.