True about cerebellar neuronal connections ?
Ans. is 'a' i.e., Climbing fibres from inferior olivary nucleusNeuronal circuit in cerebellum Afferent for cerebellum comes through two fibers : climbing fibers and Mossy fibers. Climbing fibers which brings information only from the inferior olivary nuclei and establish excitatory synapes with purkinje cells. All other afferent input to the cerebellum is brought by the other types of fibers, called Mossy fibers which establish excitatory synapse with granule cells in the granular cell layer. The axon of granule cells, called parallel fibers, stimulate the purkinje cells. Thus mossy fibers, like the climbing fibers, also end up in stimulating the purkinje cells.Granule cells are the only stimulatory (excitatory) cells in cerebellar coex.The parallel fibers (axons of granule cells) also stimulate three types of interneurons :- Stellate and basket cells in the molecular layer, and Golgi cells in the granular layer. Stellate and basket cells inhibit purkinje cells. Golgi cells, also activated by collateral from mossy fibers (besides parallel fibers), inhibit transmission from mossy fibers to granule cells.Overall, climbing fiber inputs exe a strong excitatory effect on a single purkinje cell, Whereas mossy fiber inputs exe a weak excitatory effect on many purkinje cells the granule cells.After complex inhibiting and excitatory interactions of various fibers and cells in the coex, the output of cerebellar coex, is projected to deep cerebellar nuclei by axons of pyramidal cells (only output cells of cerebellar coex). The output of the Purkinje cells is inhibitory to the deep cerebellar nuclei. However, the output of deep cerebellar nuclei to the brain stem and thalamus is always excitatory because, beside inhibitory inputs of purkinje cells, deep cerebellar nuclei also receive excitatory inputs from afferent mossy and climbing fibers which usually are more prominent.
Climbing fibres from inferior olivary nucleus
Mossy fibres from inferior olivary nucleus
Climbing fibres are inhibitory to Purkinje cells
Mossy fibres are inhibitory to Purkinje cells