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Cerebellum 1

Cerebellum 1. Objectives. Identify the major lobes and regions of cerebellum. Summarize the structure of the cerebellar cortex Identify the deep cerebellar nuclei and their connections.

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Cerebellum 1

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  1. Cerebellum 1

  2. Objectives • Identify the major lobes and regions of cerebellum. • Summarize the structure of the cerebellar cortex • Identify the deep cerebellar nuclei and their connections. • List the afferent and efferent connections of the cerebellum and their arrangement in cerebellar peduncles. • Describe the major functions of the cerebellum and how each side of the cerebellum controls the ipsilateral side of the body. • Explain the effects of lesions of cerebellum and motor disorder associated with cerbellar lesions.

  3. CEREBELLUM • ORIGIN : From the Hindbrain. • Position: Lies behind Pons & Medulla separated from them by Fourth ventricle. Situated in the posterior cranial fossa

  4. THE CEREBELLUM • It is covered by tentorium cerebelli • CONNECED TO THE BRAIN STEMBY: Inferior, Middle & Superior Cerebellar Peduncles.

  5. EXTERNAL FEATURES • It consists of two Cerebellar Hemispheres joined in midline by the Vermis. • Its surface is highly convoluted forming the Folia, separated by Fissures.

  6. EXTERNAL FEATURES • Folia: Transversely oriented gyri • 3 lobes in each hemisphere: Anterior, Posterior, Flocculonodular • Neural arrangement: Gray matter (Cortex), White matter (Internal), • Arbor vitae (tree of life): distinctive treelike pattern of the white matter Folium

  7. Vestibulocerebellum Spinocerebellum Cerebrocerebelum Cerebellum Primary fissure Anterior Lobe Regulation of muscle tone, coordination of skilled voluntary movement Posterior Lobe Planning and initiation of voluntary activity Flocculo-Nodular Lobe (FN lobe) Maintenance of balance, control of eye movements Folia

  8. ANATOMICAL SUBDIVISION • Anterior lobe: in front of primary fissure, on the superior surface. • Posterior (middle) lobe: behind primary fissure (Between Primary & Secondary fissures). • Flocculonodular lobe: in front of secondary (Posterolateral) fissure , on the inferior surface . Superior Surface Anterroinferior Surface

  9. LOBES OF CEREBELLUM Inferior surface Anterior lobe • Divisions of lobes • Anatomical • Flocculonodularlobe • Anterior lobe • Posterior lobe Posterior lobe Flocculonodular lobe Superior surface Anterior lobe Posterior lobe

  10. Arbor vitae Arbor vitae cerebelli •In latin “ tree of life” it is the white matter of cerebellum. It is so called because of the tree like appearance. It brings sensory and motor sensations to and from cerebellum. Fourth ventricle

  11. Structure of the cerebellum • Outer grey matter: cerebellar cortex. • Inner white matter: cerebellar medulla. • Deeply seated nuclei in white matter: from medial to lateral: • Fastigeal nucleus. • Globose nucleus. • Emboliform nucleus. • Dentate nucleus: largest one.

  12. CEREBELLAR CORTEX Divided into 3 layers: Outer Molecular layer Intermediate Purkinje cell layer Inner granular layer

  13. Cerebellar Medulla • Consists of three types of nerve fibres in the white matter • Axons of purkinje cells • The final output of the cerebellar cortex. The only axons to leave cerebellar cortex to end in deep cerebellar nuclei specially dendate nucleus. • Mossy fibres • Originate in all the cerebellar afferent tracts apart from inferior olive. They end in the granular layer. • Climbing fibres • Originate in the inferior olive of the medulla. They end in the molecular layer

  14. CEREBELLAR MEDULLA AFFERENT FIBRES: • Climbing fibres: from inferior olivary nucleus, relay to purkinje cells • Mossy fibres: rest of fibres: • From vestibular nuclei • From spinal cord • From pons • They relay to granulecells which in turn relay to purkinje cells

  15. CEREBELLAR MEDULLA • Axons of Purkinje Cells are the only axons to leave the cortex to medulla: • The great majority of axons do not leave cerebellum & end in deep cerebellar nuclei, specially Dentate nucleus. • Some of axons leave cerebellum as efferent fibres.

  16. CEREBELLAR MEDULLA EFFERENT FIBRES: • Most of efferent fibres are axons of deep cerebellar nuclei. • Main Efferents go to: • Vestibular nuclei • Red nucleus • Ventral lateral nucleus of thalamus.

  17. FUNCTIONAL SUBDIVISIONS OF THE CEREBELLUM

  18. Functional (Evolutionary) divisions • Paleocerebellum • Neocerebellum • Archicerebellum

  19. ARCHICEREBELLUM • Vestibular Part of cerebellum: Flocculonodular lobe. Green = Archi-cerebellum,Blue= Paleo-cerebellum. Pink= Neo-cerebellum.

  20. ARCHICEREBELLUM • Nuclei Related: Fastigeal • Afferents:from : 1- Vestibular apparatus of internal ear via vestibulo-cerebellar tracts 2- Vestibular nuclei (Vestibulocerebellarfibres),(through ICP) • Efferents:to Vestibular nuclei (through ICP) • Function:controls Balance (via vestibulospinal & reticulospinal tracts).

  21. PALEOCEREBELLUM • Spinal Part of cerebellum: Vermis & Paravermis Green = Archi-cerebellum,Blue= Paleo-cerebellum. Pink= Neo-cerebellum.

  22. PALEOCEREBELLUM • Nuclei Related: globose & emboliform • Afferents:from spinal cord (dorsal & ventral spinocerebellar tracts through ICP & SCP, respectively) (proprio-ceptiveimpulses from Ms.& tendons ) • Efferents:to red nucleus(through SCP) • Function: influences posture & muscle tone (via Rubrospinal tract).

  23. NEOCEREBELLUM • Cerebral Part of cerebellum: Rest of Cerebellum.

  24. NEOCEREBELLUM • Nuclei Related: Dentate • Afferents:It receives afferent impulses from the cerebral cortex+ pons Via cerebro-ponto- cerebellar pathway. (Pontocerebellarfibres) (through MCP) • Efferents:to Red nucleus but mostly to Ventral Lateral Nucleus of Thalamus (through SCP) then to motor cortex • Function:coordination of voluntary movements (via descending corticospinal & corticobulbar tracts).

  25. Summary of classification Classification by development Archicerebellum Paleocerebllum Neocerebellum Classification by Afferent Connection Vestibulocerebellum Spinocerebellum Pontocerebellum Classification by Efferent Connection Vermis Paravermal Region Cerebellar Hemisphere Archicerebellum Nodulus Archicerebellum flocculus Palaeocerebellum Neocerebellum Spinocerebellum Pontocerebellum Vestibulocerebellum

  26. Functions of cerebellum  Maintenance of Equilibrium - balance, posture, eye movement  Coordination of half-automatic movement of walking and posture maintenace - posture, gait  Adjustment of Muscle Tone  Motor Leaning – Motor Skills  Cognitive Function

  27. CEREBELLAR LESIONS • MIDLINE LESION: Loss of postural control. • UNILATERAL LESION: IPSILATERAL“Cerebellar ataxia” .Causes : • Incoordination of arm: intention tremor (on performing voluntary movements) • Incoordination of leg: unsteady gait • Incoordination of eye movements: nystagmus: rapid jerky eye movements • Slowness of speech: dysarthria Staccato speech

  28. Cerebellar Ataxia Ataxic gait and position: Leftcerebellar tumor a. Sways to the right in standing position b. Steady on the right leg c. Unsteady on the left leg d. ataxic gait Remember: IPSILATERAL

  29. CerebellarMedulloblastoma Cerebellar tumors on vermis - Truncal Ataxia - Frequent Falling The child in this picture: - would not try to stand unsupported - would not let go of the bed rail if she stood on the floor.

  30. SUMMARY • Anatomically, the cerebellum is divided into: anterior, posterior & flocculonodular lobes. • Developmentally & functionally, it is divided into: archi- paleo- & neocerebellum. • Archicerebellum (flocculonodular lobe) is the oldest part of cerebellum, related to fastigealnucleus, connected to vestibular nuclei & concerning for control of body balance.

  31. SUMMARY • Paleocerebellum (vermis & paravermis) is related to globose & emboliformnuclei, connected to spinal cord & red nucleus & concerned with regulation of posture & muscle tone. • Neocerebellum (most of human cerebellum) is related to dentate nucleus, connected to pons, thalamus. Its final destination is to motor cortex. It is concerned with coordination of voluntary movements. • Cerebellar lesions lead to ipsilateralincoordination (ataxia).

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