Cerebellum (Cerebellar Pathway, Cells In Cerebellar Cortex)

The cerebellum plays a critical role in coordinating and fine-tuning voluntary movements, including posture, balance, and limb coordination. The cerebellum is also involved in several cognitive processes, including attention, language, and working memory.

A thorough understanding of the cerebellar pathway and its components is essential for diagnosing and treating motor disorders.

Read this blog further and get a quick overview of this important Anatomy topic for NEET PG exam preparation.

• Spino cerebellar tract carry unconscious proprioception of lower limb to cerebellum 

CEREBELLAR ATAXIA

Due to injury to spinocerebellar tract [anterior lobe] there are present Uncoordinated clumsy movements like patient is not  able to walk in straight line [loss of coordination] and also Keep falling towards side of lesion. in these patients the HEEL SHIN TEST positive , in this we  Ask the patient to  move his heel on his Shin if he is Unable to do so then this test is considered to be  POSITIVE.

• Intentional tremor present 

CEREBELLUM

Cerebellum present in posterior cranial fossa . It is Leaf like [foliated ] structure Present at the roof of the 4th ventricle. It Attaches to the brain stem with the help of peduncles. 

• Superior peduncle with midbrain 
• Middle peduncle  with pons 
• Inferior peduncle  with M. Oblongata 

A midline vermis separates the cerebellum's left and right hemispheres. The cerebellum has folia, or folds, and fissures on its outside, which give it a wavy look. The cerebellum's lobes are separated by some of the fissures, which serve as landmarks:

• The smaller anterior and bigger posterior lobes are separated by the major fissure.
• The flocculonodular lobe is separated by the posterolateral fissure.
• The cerebellum is split into superior and inferior sections by a horizontal fissure, yet it is not believed that this division has any functional significance.

LOBES of cerebellum:

• ANTERIOR LOBE also known as Paleocerebellum  
• POSTERIOR LOBE also known as NEO CEREBELLUM 
• FLOCCULONODULAR LOBE also known as  ARCHICEREBELLUM

Tracts carried by peduncles are:

• Middle cerebellar peduncle carries Ponto cerebellar tract 
• Superior cerebellar peduncle carries Dentato thalamic tract 
• Inferior cerebellar peduncle carries Spino cerebellar tract 

CEREBELLAR PATHWAY

→ Rt. LL moving 

↓

Rt. dorsal spinocerebellar tract activated 

↓

positional sense carried towards rt. cerebellum 

↓

cerebellum communication with C/L thalamus via dentato thalamic tract 

↓

Thalamus communicates with left cerebellum 

↓

Rt. LL moved by Lt. cerebellum via cortico spinal tract [crossing occurs in lower medulla]

MOSSY FIBRES

Numerous of these fibres are derived from the spinal cord, vestibular nuclei, and pontine nuclei. These fibres connect excitably to the granule cells and deep cerebellar nuclei. Mossy fibres attach to the granule cells' dendrites. 'Glomeruli' are composed of mossy fibres and golgi cells. These fibres originate in the deep nuclei and enter the cerebellum from there. Additionally, they do so through Purkinje cells, parallel fibres, and granule cells, which project to the deep nuclei.

Cerebellum Lesions Causes Ipsilateral Manifestations

CEREBELLAR CORTEX – LAYERS

1. Molecular layer [outer]
2. Purkinje layer
3. Granular layer [Inner]

• Vermis → Present in midline, most medial, oldest
• Primary fissure → Separate anterior & posterior lobes
• ARBOR VITAE → White matter of cerebellum

DEEP CEREBELLAR NUCLEI [DEFG]                                  

• D → Dentate Nucleus
• E → Emboliform Nucleus
• F → Fastigial Nucleus
• G → Globose Nucleus

• → Emboliform nucleus INTERPOSED NUCLEI ,Globose nucleus
• →Dentate Nucleus → most lateral, latest
• →Fastigial Nucleus → most medial, oldest

Revision

Lesions

Cells in Cerebellar Cortex

3 Layer and 5 cells in cerebellar cortex

• Outer molecular layer Contains stellate & basket cells
• Middle Purkinje layer Contains purkinje's cells(processes goes to outer molecular layers)
• Inner granular layer Contains granule & Golgi cells

• CLIMBING FIBRES  → Comes from inferior olivary nucleus of medulla oblongata 
• MOSSY FIBRES   → Most predominant 
• PURKINJE CELLS → Only efferent cells of cerebellar cortex.  

                                         Flask shaped cells with multiple projections into outer molecular layer

CEREBELLAR AFFERENT PATHWAYS

Fibers reach cerebellum Synapses with granule cells which communicate with remaining cell fibers. Granule cells use parallel fibers to communicate with other cells. Purkinje cells can only reach the DEFG nucleus. Most of mossy fibers runs as dorsal/ ventral spinocerebellar tract & reaches ipsilateral cerebellum and Very few crosses midline in spinal cord & runs as ventral/ anterior spinocerebellar tract & recrossing occurs within cerebellum and reaches ipsilateral cerebellum. Dorsal spinocerebellar tract uses inferior peduncle & reaches I/L cerebellum. Ventral spinocerebellar tract uses superior peduncle & reaches C/L cerebellum but recrossing occurs & reaches I/L cerebellum again. Climbing fibers Comes from inferior olivary nucleus of medulla oblongata and goes to purkinje cell in cerebellar cortex.

CEREBELLAR PATHWAYS

• CEREBRO PONTO CEREBELLAR TRACT 
  • → via middle cerebellar peduncle, useful in FEEDBACK/ LOOP MECHANISM 

INCOMING FIBRES & CEREBRAL PEDUNCLES 

• Inferior cerebellar peduncle
  • Olivo cerebellar tract 
  • Dorsal spinocerebellar tract 
• Middle cerebellar peduncle  
  • Cortico ponto cerebellar tract
• Superior cerebellar peduncle 
  • Ventral spinocerebellar tract 

Outgoing Fibres & Cerebellar Peduncles

• Superior cerebellar peduncle 
  • → Dentato rubro thalamic tract

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