Medical brain notes 24

  Basic Structure of the Cerebellar Cortex       In striking contrast to the cortex of the cerebral hemispheres, the cerebellar cortex has a uniform structure in all parts of the cerebellum. It may be divided into three layers (Fig. 12.1) as follows. a.                M o lecular layer  (most superficial). b.                Purkinje cell layer . (The Purkinje cell layer is often described as part of the molecular layer). c.                 Granular layer , which rests on white matter. The neurons of the cerebellar cortex are of five main types. a.                Purkinje cells , forming the layer named after them. b.          ...

  Main Connections of the Cerebellum             The fundamental points to be appreciated in considering the connections of the cerebellum are that, as a rule (Fig. 12.5): 1.                afferent fibres terminate in the cortex; 2.                efferent fibres arising in the cortex end in cerebellar nuclei; and 3.                fibres arising in the nuclei project to centres outside the cerebellum.         There are, however, important exceptions to these rules. Some fibres (notably vestibular) project directly to the cerebellar nuclei. Some parts of the cortex give off efferents that bypass the nuclei to reach centres outside the cerebellum.       ...

  Connections between Cerebellum and Spinal Cord       From a clinical point of view the most important connections of the cerebellum are with the spinal cord, and with the cerebral cortex. These connections are through various pathways that are summarised below.          Spinocerebellar pathways convey to the cerebellum proprioceptive information necessary for controlling muscle tone and for maintaining body posture. These pathways also carry exteroceptive impulses. Direct pathways from spinal cord to cerebellum         These are the ventral spinocerebellar tract, and the dorsal spinocerebellar tract which convey information from the hind limb. Information from the forelimb is probably conveyed by the rostral spinocerebellar tract and the cuneocerebellar tract. The cuneocerebellar tract begins in the medulla, but is included here as it is functionally equivalent to spinocerebellar t...