• Control of movements
Each of the three functional regions of the cerebellum influences a different parameter of motor function, and each uses the corresponding cerebellar nuclei i. e.
• The cerebrocerebellum is involved in planning and initiation of motor function
• The spinocerebellum oversees the actual execution and the coordination of motor event
• The vestibulocerebellum functions during the execution of the motor activity to maintain and adjust body posture.
Motor plasticity and Learning
- The word learning as used in this case refers to the ability to modify motor responses or sequences to a new situation, or changes in the surrounding conditions.
- Although many movements are reflex responses, and are preprogrammed in the central pattern generators (CPG's), motor actions are normally very plastic and adaptable to change.
Modifications of stretch reflex
- When dorsiflexion of the foot is produced by tilting the floor, and not the body, reflex contraction of the gastrocnemius causes the individual to fall back.
- In this reflex, cerebellar afferents enter the spinocerebellum as mossy fibre afferents.
- Afferents also reach the cerebral cortex. Signals from the cerebral cortex project to the cerebellum via the inferior olivary nucleus, and climbing fibre system.
- These are the signals that are responsible for the adaptive changes. With repeated stretching of the muscles, the stretch reflex response becomes diminished, i.e. it becomes altered to meet the current environmental circumstances.
Regulation of autonomic activity
- The cerebellum is active in the planning, coordination and execution of somatomotor activity.
- The hypothalamus is among the chief modulators of visceromotor activity.
- The hypothalamocerebellar and cerebellohypothalamic pathways provide direct connections between the integrative centres for visceromotor and somatomotor activity.
- Through these direct connections, the visceromotor systems , can anticipate the visceromotor needs of somatic tissue and continuously monitor the demands of new steady states, i.e. metabolic and vasoregulatory requirements of specific muscle groups during somatomotor activity, in progress or anticipated
|
