Cerebellum & Diencephalon

Section 3

cerebellum

The cerebellum is an automatic processing center that has two primary functions: 1) serve to maintain posture and equilibrium by adjusting the postural muscles of the body 2) smoothes and coordinates voluntary and involuntary movements ordered by other brain regions Damage to the cerebellum will cause victims: 1) disorders of equilibrium exhibiting a wide stance and unsteady drunken sailor gait 2) disorders of coordination exhibiting slow or jerky movements that are inaccurate and tend to overreach their targets;

The position of the cerebellum 位置 Lies in the posterior fossa of the cranial cavity / inferior to the occipital lobe of the cerebrum / posterior to the brain stem Connected to midbrain, pons and medulla oblongata by superior, meddle and inferior peduncles respectively

Superior cerebellar peduncle Meddle cerebellar peduncle

Inferior cerebellar pecuncle

Vermis

External appearance Division

Primary fissure

Hemispheres 半球 Vermis 蚓

Superior semilunar lobule

Structures on the surface Primary fissure 原裂 Horizontal fissure 水平裂

Horizontal fissure

Flocculus 绒球 Nodule 小结

Superior aspect

Tonsil of cerebellum 小脑扁桃体

Vermis

( tonsillar hernia 扁桃体疝 )

Uvula of vermis 蚓垂

Inferior semilunar lobule Meddle cerebellar peduncle Flocculus Superior cerebellar peduncle

Pyramid of vermis 蚓锥 Nodule

Tonsil of cerebellum Uvula of vermis

Posterolateral fissure

Pyramid of vermis

Inferior aspect

Lobes of the cerebellum Flocculonodular lobe 绒球小结叶 : The oldest part of the cerebellum / archicerebellum 古小脑 ； being vestibular in its connections / vestibulocerebellum 前庭 小脑

Anterior lobe 前叶： appear next to flocculonodular lobe / paleocerebellum 旧小脑 ； being spinocerebellar in its connections / spinocerebellum 脊髓小脑

Posterior lobe 后叶 ： appear the latest / neocerebellum 新小脑 ； being corticopontocerebellar in its connections / pontocerebellum 脑桥 小脑

spinocerebellum

pontocerebellum

vestibulocerebellum

Anterior lobe

Posterior lobe

Flocculonodular lobe

Cerebellar nuclei

小脑核

The cerebellar hemisphere is covered by a layer of grey matter called cerebellar cortex, and deep to it is the white core consisting of nerve fibers. Three groups of grey masses are embedded in the core: 1)

Dentate nucleus

2)

Emboliform nucleus 栓状核 globose nucleus 球状核

3)

Fastigial nucleus

齿状核

顶核

Association cortex

Motor cortex

Vestibular ganglion

Corticopontine T. Pontine nuclei Pontocerebellum Motor cortex

vestibulocerebellum (Flocculonodular lobe)

Oculomotor N.

Thalamus

Troclear N. Red N.

Spinocer ebellum

Vestibular nucleus

Abducent N. Vestibulospinal T.

Reticular formation Motor cortex Rubrospinal tract

Spinocere belar T.

Oculomotor N. Troclear N.

Reticulospinal T.

vestibulocerebellum

thakamus

Spinsl gsnglion Red N. Corticopon tine T.

Vestibular N.

Spinocerebellar T. Spinocerebellum Thalamus Motor cortex

Motor neuron

Abducent N.

Vestibulospinal tract

Red nucleus

Pontine nuclei Rubrospinal T. Corticospi Corticospinal T. nal T.

Vestibular ganglion Lateral vestibulospinal tract

The cerebellar peduncles The fibers tract conveying information into or out of cerebellum Inferior cerebellar peduncle: composed mainly of posterior spinocerebellar T., vestibular nerve and nuclei; Meddle cerebellar peduncle: ( brachium pontis 脑桥臂 ) composed almost exclusively of the pontocerebellar fibers; Superior cerebellar peduncle: consisting mainly of the efferent fibers from the dentate, Globose and emboliform nuclei; afferent fibers of anterior spinocerebellar tract

Anterior spinocerebellar T.

Superior cerebellar Superior peduncle cerebellar

peduncle

Dentate N.

Inferior cerebellar peduncle Meddle cerebellar peduncle

Diencephalon

间脑

Three main structures: dorsal thalamus 背侧丘脑 , hypothalamus 下丘脑 and epithalamus 上丘脑 ; Minor structures: subthalamus 底丘 脑 and metathalamus 后丘脑

The superior view of the diencephalon: 1)

Medial part of the dorsal thalamus is visible and the third ventricle lies between two thalamus

2)

Lateral part of the dorsal thalamus is covered by caudate N.

Lateral to thalamus is the lentiform N.

View on the horizontal section 1)

Dorsal thalamus lies posteromedial to the lentiform N. and internal capsule is visible between them;

2)

Head of the caudate N. is visible anterolateral to thalamus;

3)

The third ventricle lies between left and right thalamus

View on the coronal section: 1)

On both sides of the third ventricle are the left and right thalamus

2)

Internal capsule separates the thalamus from lentiform N.

3)

Caudate N. is above the thalamus

4)

The subthalamic N.is under the thalamus and so is the red N.

The nuclear groups of thalamus: Anterior group Medial group dorsomedial nucleus Lateral group: 1) dorsal part 2) ventral part ventral posterolateral N. ,ventral posteromedial N. ,medial and lateral geniculate N.

The thalamus is divided into three main groups of grey matter by internal medullary lamina; All nuclei of the thalamus are functionally distinguished as 1) specific thalamic nuclei （ ventral posterolateral N. ventral posteromedial N. medial geniculate N. and lateral geniculate N.) 2) nonspecific thalamic nuclei

View of the thalamus in situ : 1)

The thalamus consists of A, VA, MD, MTT;

2)

IC represents the internal capsule;

3)

C represents the caudate N.

4)

The lentiform N. is composed of P, GPI and GPM

About specific thalamic nuclei: The ventral posterior nucleus are specific sensory nucleus; 1) The ventral posterolateral nucleus relays the sensory fibers from the medial lemniscus and spinothalamic lemniscus; The relayed fibers leaving the ventral posterolateral nucleus, travel through the internal capsule and terminate in the sensory area of cortex in the parietal lobe.

2) The ventral posteromedial nucleus relays the fibers from the trigeminal lemniscus;

The relayed fibers travel through the Internal capsule and end in the primary somatic sensory area of the cortex

Lateral geniculate body LGB and medial geniculate body MGB are specific relay nuclei for the fibers of optic tract and the fibers of hearing from cochlear nucleus respectively ; LGB gives rise to the optic radiation ending in visual area of cortex; MGB gives rise to the acoustic radiation ending in auditory area of cortex

Lateral geniculate body

Medial geniculate body

Metathalamus

后丘脑

Medial geniculate body

内侧膝状体

Lateral geniculate body 外侧膝状体

Epithalamus 上丘脑 Thalamic medullary stria 丘脑髓纹 Hebenular trigone 缰三角 Hebenular commissure 缰连合 Pineal body 松果体

Subthalamus

底丘脑

Subthalamic nucleus 底丘脑核

Hypothalamus 下丘脑 The portion of the diencephalon ventral to the hypothalamic sulci surrounding the third ventricle; It is divided into 1)optic chiasma 视交叉 2) tuber cinereum and infundibulum 灰结节、漏斗 3)mamillary body 乳头体 Functions of the hypothalamus Hypothalamus contains nuclei involved in visceral processes and emotions, forms the link between the nervous and endocrine system; It has also been demonstrated to control a variety of autonomic functions

The main nuclei of the hypothalamus: 1)

Supraoptic nucleus 视上 核 secretes antidiuretic hormone

2)

Pareventricular nucleus 室旁核 secretes oxytocin, causing smooth muscle contractions in uterus

3) Suprachiasmatic nucleus 视交叉上核 regulates daily rhythms

4) Preoptic nucleus 视前核

regulates body temperature via control of autonomic centers in the medulla

5) Tuberal or arcuate nucleus 弓状核 produces inhibitory and releasing hormones that target anterior pituitary

Electrical stimulation of some regions give rise to parasympathetic response, and others give rise to sympathetic response; Autonomic centers adjust and coordinate visceral activities, such as heart rate, blood pressure, respiration and digestive functions