Cerebellum and control of postures and movements.pptx

Cerebellum and control of postures and movements

1. Cerebellum and Control of postures and movement S. Parasuraman, M.Pharm ., Ph.D., Associate Professor, Faculty of Pharmacy, AIMST University

2. Learning Outcomes At the end of this session, the student would be able to: Explain the anatomy and Functions of the Cerebellum Explain the Regulation of Posture and voluntary movements Explain the role of the Cerebellum in Motor skills learning Explain the abnormalities in motor function in a patient with cerebellar disorder and provide the best insight into the function of the organ.

3. Cerebellum The cerebellum is situated behind the pons and immediately below the posterior portion of the cerebrum occupying the posterior cranial fossa. It is ovoid in shape and has two hemispheres, separated by a narrow median strip called the vermis . The vermis, which is a central constricted area, connects the hemispheres. Grey matter forms the surface of the cerebellum, and the white matter lies deeply.

4. Cerebellum The cerebellum is similar to the cerebrum in that each has hemispheres that control the opposite side of the body and are covered by gray matter and surface folds.

5. Functions of cerebellum The cerebellum is concerned with the coordination of voluntary muscular movement, posture and balance . It coordinates activities associated with the maintenance of the balance and equilibrium of the body. Damage to the cerebellum results in clumsy uncoordinated muscular movement, staggering gait and inability to carry out smooth, steady, precise movements. It is also involved in certain cognitive functions , such as language . The cerebellum plays a major role in adapting and fine-tuning motor programs to make accurate movements through a trial-and-error process .

6. Functional Subdivisions of the Cerebellum Vestibulocerebellum : It is involved in vestibular reflexes and in postural maintenance . Spinocerebellum : It is involved in the integration of sensory input with motor commands to produce adaptive motor coordination. Cerebrocerebellum : It is involved in the planning and timing of movements . In addition, the cerebrocerebellum is involved in the cognitive functions of the cerebellum . Ref: https://nba.uth.tmc.edu/neuroscience/m/s3/chapter05.html [Last assessed on 06/11/2018]

7. Functional Subdivisions of the Cerebellum Other functions: Influence on autonomic system ( mediated through the hypothalamus and reticular formation ) Influence on conduction in ascending sensory pathway (through the reticular formation and thalamus) Control of eyeball movements (through vestibular nuclei)

8. Control of body posture and movements Postural control is defined as achievement, maintenance or regulation of balance during any static posture or dynamic activity for the regulation of stability and orientation.

9. Control of body posture and equilibrium Afferents to cerebellum: . Vestibulocerebellar tracts: carry input from the vestibular nuclei, which convey afferents from the macula of saccule and utricle for static equilibrium and from the ampullary crests of semicircular ducts for kinetic equilibrium.

10. Control of body posture and equilibrium Afferents to cerebellum: . Spinocerebellar and cuneocerebellar tracts : carry feedback about tone of muscles or position of the limbs in space. Reticulocerebellar tracts: bring feedback about activities of extrapyramidal tracts.

11. Control of body posture and equilibrium Efferents to cerebellum: . The flocculonodular lobe and fastigial nuclei project output fibres through inferior peduncle to vestibular and reticular nuclei of brain stem. The vermal cerebellum sends back the information to spinal cord indirectly through fastigial nuclei . cerebellum does necessary corrections for maintaining posture and equilibrium without participation of conscious

12. Control of muscle tone and stretch reflexes Afferents to cerebellum: . Spinocerebellar , cuneocerebellar and olivocerebellar tracts carry proprioceptive and tactile inputs from the limbs, trunk, neck and other parts of the body. Spinocerebellum also receives auditory and visual impulses through tectocerebellar tract.

13. Control of muscle tone and stretch reflexes Efferents to cerebellum: The spinocerebellum is projected into the cerebellar nuclei— fastigii , emboliformis and globossus . Spinocerebellum regulates the postural reflexes by modifying muscle tone.

14. Control of voluntary movements Cerebellum is not able to initiate any motor activity , but coordinates movements initiated by the motor cortex . Control of movements by cerebellum includes regulation of time, rate, range (extent), force and direction of muscular activity.

15. Control of voluntary movements Pathway of control of voluntary movements: Open feedback loop: Also known as cerebro-cerebellocerebral connection or afferent efferent circuit consists of “ Cerebro - ponto -cerebellar tract ” and “ Dento - rubro -thalamic cortical tract ”. Closed feedback loop: It is formed by the fibres from the cerebral motor cortex to the paravermal cerebellum to the cerebral motor cortex.

16. Thank you