After completing this study unit you will be able to:
- Understand the internal structure of the cerebellum and divisions of the gray matter inside the cerebellum.
- Learn about the nuclei of the cerebellum, their structure and functions.
The gray matter structures are the cerebellar cortex and cerebellar nuclei. The cerebellar cortex is the superficial sheet of densely packed nerve cells organized into three distinct layers (from superficial to deep):
- Molecular layer
- Purkinje cell layer
- Granular layer
The deep gray matter is embedded in the white matter of the cerebellum and organized in four deep cerebellar nuclei. These nuclei are arranged in the following order (medial to lateral):
- Fastigial nuclei
- Globose nuclei
- Emboliform nuclei
- Dentate nuclei
The globose and emboliform nuclei can functionally be grouped into a structure called the interposed nuclei.
Although output from the cerebellum originates from both the cerebellar cortex and nuclei, it should be noted that the latter are by far the main source of cerebellar output.
This video tutorial will provide you with an overview of the cerebellar nuclei.
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Take a closer look at the cerebellar nuclei in the gallery below.
Medial (vermal) zone (zone A), vestibular nerve (CN VIII), vestibular nuclei
Descending fibers: project primarily to vestibular nuclei (→ vestibulospinal tract) and reticular formation in pons and medulla (→ reticulospinal tract).
Ascending fibers: nuclei of oculomotor nerve, superior colliculus, thalamus and hypothalamus
Vestibulospinal and reticulospinal tracts form medial descending system → involved in maintenance of balance and posture as well as muscle tone of extensor muscles
Intermediate (paravermal) zone (C1 & C3 → emboliform nucleus, C2 → globose nucleus)), spinocerebellar tracts
Contralateral red nucleus ( → rubrospinal tract), ventrolateral nuclei of thalamus (projects to primary motor and premotor cortex → lateral corticospinal tract).
Execution and modulation of movement, rubrospinal and lateral corticospinal tracts form lateral descending system → influence movements of distal musculature of limbs
Lateral zone (D zones), cerebral cortex via pontine nuclei
Dorsal/motor part: contralateral ventrolateral (VL) nuclei of thalamus (project to primary motor and premotor cortex → lateral corticospinal tract), red nucleus and nucleus of oculomotor nerve
Ventral nonmotor part: projects to prefrontal and parietal cortices via VL nuclei of thalamus
Dorsal/Motor part: Planning, initiation and timing of voluntary movement (e.g. reciprocal action of agonist and antagonist muscles of the limbs), modulation of oculomotor movement
Ventral/nonmotor part: Associated with cognitive and visuospatial functions of cerebellum
|Each cerebellar nucleus projects efferent fibers to the inferior olivary complex as well as reciprocal fibers to regions of cerebellar cortex that project to it