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Home , Deep cerebellar nuclei, Dentate nucleus, Flocculonodular lobe, Globose nucleus

Anatomy of & Relevant Connections

Neuroanatomy block-Anatomy-Lecture 14

Editing file Objectives

At the end of the lecture, students should be able to:

● Describe the external features of the cerebellum (lobes, fissures). ● Describe briefly the internal structure of the cerebellum. ● List the name of cerebellar nuclei. ● Relate the anatomical to the functional subdivisions of the cerebellum. ● Describe the important connections of each subdivision. ● Describe briefly the main effects in case of lesion of the cerebellum. Color guide

● Only in boys slides in Green ● Only in girls slides in Purple ● important in Red ● Notes in Grey The Cerebellum

Origin : from ,lies behind & Medulla Separated from them by Fourth ventricle.

Connection To Brain Stem : by inferior, middle & superior cerebellar peduncles.

External Features: It consists of two cerebellar hemispheres joined in midline by the vermis Its surface is highly convoluted forming folia separated by fissures.

Anatomical Subdivision

Posterior (middle) lobe: : Anterior lobe: in front behind primary fissure in front of secondary of primary fissure on (Between Primary & (Posterolateral) the superior surface. Secondary fissures fissure on the inferior = posterolateral) surface .

3 Constituents Internal Structure and Nuclei of Cerebellum

Inner : cerebellar medulla. Afferent Fibres: (4 afferent fibers) Deeply seated nuclei in ● Outer : Climbing fibres: (direct to purkinje cells). from inferior olivary , relay to purkinje cells white matter: ● cerebellar cortex Mossy fibres: (indirect to purkinje cells) rest of fibres: from medial to lateral: Divided into 3 layers: 1. From 2. From 3. From pons 1. Fastigial: smallest one 1. Outer molecular layer They relay to granule cells which in turn relay to purkinje cells and most medial also called 2. Intermediate Purkinje Finally all afferent fibres passing through the medulla relay to purkinje cells in the cortex. 2. Globose. interposed cell layer 3. Emboliform. nucleus 3. Inner granular layer Axons of purkinje cells are the only axons to leave the cortex to medulla: 4. Dentate: largest one 1. The great majority of axons do not leave cerebellum & end in . specially and most lateral . . 2. Some of axons leave cerebellum as efferent fibres.

Efferent Fibres: (3 efferent fibers) Most of efferent fibres are axons of deep cerebellar nuclei. Main efferents go to: 1. Vestibular nuclei (cerebello-vestibular tract). 2. (Dendato-rubro-thalamic tract). 3. Ventral lateral nucleus of (Dendato-thalamic tract).

4 Functional Subdivisions Of The Cerebellum

Archi-Cerebellum Paleo-Cerebellum Neo-cerebellum (Vestibular Part) (spinal part) (Cerebral Part)

Part of flocculonodular lobe vermis & paravermis Rest of cerebellum cerebellum

Nuclei Fastigial Globose & Emboliform Dentate

from Vestibular nuclei From spinal cord (dorsal & From Pons (Pontocerebellar fibres) (Vestíbulo-Cerebellar fibres) ventral spinocerebellar through MCP. Afferent through ICP tracts through ICP & SCP, respectively)

to cortical () to globose & emboliform to Red nucleus but mostly to Fibres project : to Fastigial nuclei which project to red Ventral Lateral Nucleus of Efferent nucleus, which projects to nucleus through SCP. Thalamus (through SCP) then to vestibular nuclei through ICP + to

-Controls body Balance Controls and influence Coordination of voluntary (via vestibulospinal & posture & muscle tone movements reticulospinal tracts). (via ). (via descending corticospinal & Function -Control of eye movement corticobulbar tracts or rubrospinal (via VO vestibulo-ocular tract). reflex)

5 Cerebellar Lesions

Midline Lesion 2 Unilateral Lesion

Cerebellar causes ipsilateral: Loss of postural control ● Incoordination of arm: (on performing voluntary movements) 1 ● Incoordination of leg: unsteady gait ● Incoordination of eye movements: nystagmus. ● Slowness of speech: dysarthria(difficulty of speech)

6 Practice Q1: The nuclei related to paleocerebellum are? Q5: The most medial nuclei in white matter is ? A. Globose & Dentate A. B. Dentate & Fastigial c. B. . Globose & Emboliform C.Emboliform nucleus. D. Emboliform & Fastigial D. Dentate nucleus Q2: ______Climbing and mossy fibers relay to ______? Q6:To which of the following does main efferent go to? A.Afferent, purkinje cells A.Ventral medial nucleus of thalamus B. Afferent, Inner granular layer B.Emboliform nucleus C.Efferent, Inner granular layer C.Red nucleus D. Efferent, purkinje cells D.Globose nucleus Q3: which one of the following Archicerebellum control? Q7: Neocerebellum coordinate voluntary movements via? A. Body Balance A.Vestibulospinal & reticulospinal tracts B. Posture B. Descending corticospinal & reticulospinal tracts C. Memory and speech C. Vestibulospinal & cortico bulbar tracts D. All of the above D.Descending corticospinal & corticobulbar tracts Q4: The cerebellum originates from the dorsal aspect of the brain stem and Q8 From which nucleus afferent fibers go directly to purkinje cells? overlies the ______? A. Fastigial A. Fourth ventricle B. vestibular nuclei B. Third ventricle C. C. Midline ventricle D. Red nucleus D. Lateral ventricle

Answers: Q1(C) Q2(A) Q3(A) Q4(A) Q5(A) Q6(C) Q7(D) Q8(C) 7 Members board

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