Function of the cerebellum

Functional anatomy of the Cerebellum
The Cerebellum consists of:
 * 1) the cortex which is the area that receives and integrates all the afferent inputs entering the cerebellum. The integrated signal is transmitted to the cerebellar nuclei in the white matter,
 * 2) the cerebellar nuclei which receive directly afferent inputs and integrated inputs from the cerebellar cortex. It is the area where all efferent output signals leave the cerebellum,
 * →Dentate nucleus
 * →Emboliform nucleus
 * →Globose nucleus
 * →Fastigial nucleus


 * Flocculonodular compartment: also called the vestibulocerebellum, where vestibular efferents from the vestibular nuclei enter and inform the cerebellum about the orientation of the head and body in space and gravitational field. This information derive from the vestibular apparatus in the inner ear (semicircular canals, utricle and saccule).
 * Vermis: also called the spinocerebellum, where somatosensory efferents enter and inform the cerebellum about stimuli applied on cutaneous receptors and proprioceptors in deep structures such as muscles. This information derive for example from the Meissner' s corpuscle mechanoreceptors in the thick skin of the foot plantar aspect (cutaneous) and from Golgi tendon organs and muscle spindles in the muscles (proprioception).
 * Lateral hemispheres: also called the cerebrocerebellum, where cortical efferents enter and inform the cerebellum about motor program of the cerebral cortex. For example, motor activities from the motor cerebral cortex through corticobulbar and corticospinal tracts are inspected by the cerebellum.

Function of the Cerebellum
Primarily, Cerebellum acts as a comparator that compensates for errors in the movement by comparing and contrasting intention with performance. It receives information about the desired program of muscle contraction from the cortical motor areas. It also receives continuous updated sensory information from the periphery about the present state of muscles and compares that state with the desired program and if there are any deviations, it acts in order to restore them in order to induce the appropriate performance of a movement:
 * Control of Muscle tone
 * Control of Posture and Equilibrium
 * Control of Voluntary movements

Cerebellar Reflex Arc
In order for the cerebellum to perform its functions it requires sensory input from many different parts of the human body including the brain, subcortical structures and periphery. The signals are transmitted to the cerebellum where they are integrated and passed to the cerebellar nuclei. From their efferent output leaves the cerebellum and reaches various structures. This process is referred to as the reflex arc of the cerebellum and consists of:
 * 1) Sensory receptors
 * 2) Afferent pathways
 * 3) CNS
 * 4) Efferent pathways
 * 5) Effectors

1. Sensory receptors

 * Cutaneous receptors: they are mechanoreceptors that detect primarily tactile stimuli. The most important cutaneous mechanoreceptors for the cerebellar functions are the Meisner's corpuscles that are located in the non hairy body skin areas, especially in finger tips and soles. These provide information about the contact of feet with the ground playing a key role for maintenance of muscle tone and equilibrium along with posture from the cerebellum.
 * Proprioceptors: they are receptors found in muscles. The muscle spindles give information about the tension of the muscle of intersest and the Golgi tendon organs provide information about the tension of tendons induced by muscle stretching

a) Afferent pathways from brain

 * Corticopontocerebellar tract: originates mainly in the motor premotor areas. It passes by way of the pontine nuclei and pontocerebellar tract to the contralateral cerebellar hemisphere.
 * Olivocerebellar tract: originates in the brain stem inferior olivary nucleus which receives input from the Basal Ganglia, Reticular formation, motor cortex and spinal cord.
 * Vestibulocerebellar tract: originates in the vestibular nuclei and terminates in the flocculonodular cerebellar area.
 * Reticulocerebellar tract: originates in different levels of the reticular formation and terminates mainly in vermis.

b) Afferent pathways from periphery

 * Posterior spinocerebellar tract
 * Anterior spinocerebellar tract