Afferent and efferent connections of the cerebellum are shown in this scheme.
Tracts inside the cerebellar peduncles
Afferent tracts are placed in all cerebellar peduncles, by which they reach all cerebellar parts (vestibulo-, spino- and ponto- cerebellum). The largest inputs are the cortical inputs, interpolated in the pontine nuclei. They run through the middle cerebellar peduncles (brachia pontis).
Efferent tracts running to the thalamus, red nucleus and reticular formation nuclei are localized in the superior cerebellar peduncles (brachia conjunctiva). For more information look at the scheme.
Superior cerebellar peduncle (brachium conjunctivum)
Cerebello-thalamic tract – „answer“ (about the body position) sended from the cerebellum to the cortex, before intended movement
Cerebello-rubral tract – information to the control cerebellar circuit and to the brain stem motor systems
Cerebello – reticular tract – information to the brain stem motor circuits
Spino-cerebellar ventral tract – kinetic constituent of the proprioception from the contralateral lower limb
Middle cerebellar peduncle (brachium pontis)
Pontocerebellar tract – „question – what is the body position?“ sended from the cortex to the cerebellum before the intended movement
Inferior cerebellar peduncle (corpus restiforme)
Spino-cerebellaris dorsal tract - kinetic constituent of the proprioception from the ipsilateral lower limb
Bulbo-cerebellar tract –static constituent of the proprioception from all limbs
Cuneo-cerebellar tract– - kinetic constituent of the proprioception from upper limbs
Olivo-cerebellar tract – information about the current commands for execution of a motion, part of the control circuit
Vestibulo-cerebellar tract – information about the position and movements of the head. hlavy
Reticulo-cerebellar tract – information about the intended movement modificated from other structures (e.g. from the limbic system).
Cerebello-vestibular tract – muscle tone adjustment and coordination of the axial muscles (mainly extensors).
Cerebello-reticular tract (from the fastigial nucleus) – information to the brain stem motor circuits
The main function of the cerebellum is the maitenance of the upright posture and balance, muscle tone regulation, control of individual movements and coordination of motions.
Main cerebellar afferents come from the spinal cord, vestibular apparatus and cerebral cortex. Afferents from the spinal cord convey impulses from the proprioreceptors and skin receptors by the ventral and dorsal spino-cerebellar tracts, by the spino-bulbo-cerebellar, spino-cuneo-cerebellar and spinocerebellar tract to the cerebellar cortex. Afferents from the vestibular apparatus run directly and undirectly (with interpolation in the vetibular nuclei) to the neurons of the nodule and floccule. They convey information about the position and movements of the head for the oculomotory and neck muscles (maitenance of the gaze direction).
Afferents from the motor, premotor, sensory and visual cortex containing the plan for the indended movement descend in the anterior and posterior limb of the internal capsule to the crura mesencephali and after the interpolation in the pontine nuclei they reach through the brachia pontis the cerebellar cortex.
Main cerebellar efferents have origin in the cerebellar nuclei and they run to the thalamus. They continue to the motor cortex after the interpolation in the thalamic VA and VL nuclei. By the main cerebellar circuit (cortex- pontine nuclei- cerebellum-thalamus-cortex) the motor cortex recieves the information for the movement execution. Other cerebellar efferents run to the reticular formation, red nucleus, vestibular nuclei and inferior olive.
Cerebellar efferents are interpolated in the thalamus directly to the motor cortex (from where the pyramidal tract for the voluntary movements has origin), in the red nucleus, reticular formation and vestibular nuclei to the brainstem motor circuits and in the inferior olive back to the cerebellum(control circuit).Direct efferents from the cerebellar cortex are few. They have origin in the nodule and floccule and they run to the vestibular nuclei, reticular formation and oulomotory nerve nuclei. They serve for the coordination of the eye movements with the head movements.