Cerebellum Prof K Sivapalan Cerebellum It has a

Cerebellum. Prof. K. Sivapalan

Cerebellum • It has a central structure called vermis and lateral structures known as cerebella hemispheres. • It is connected to brain stem by superior, middle and inferior peduncles. • It is situated above the fourth ventricle. • 150 g. 2/28/2021 Cerebellum 2

Cerebellum- structure • Anatomically, anterior, posterior and flocculonodular lobes. • Hemispheres are extensively folded and fissured than cerebral cortex • Weight is 10 % of the cerebral cortex but surface area is 75 %. 2/28/2021 Cerebellum 3

Evolution of Cerebellum • Developed in fish with vestibular apparatus • With quatrupedal locomotion anterior lobes became connected to spinal cord • Erect posture and skilled movements resulted in linkages between posterior lobe and cerebral cortex 2/28/2021 Cerebellum 4

Functional divisions • Floculonodular lobe- is also known as vestibulocerebellum. [oldest] • Rest of the vermis and medial portions of the hemispheres are known as spinocerebellum • Lateral portions of the hemispheres are Neocerebellum- [gratest in humans]. Also known as cerebrocerebellum. 2/28/2021 Cerebellum 5

Function of cerebellum. • Floculonodular lobe is concerned with equilibrium and vestibulo-occular reflex. • Spinocerebellum receives proprioceptive impulses from the body and the motor plan from the motor cortex. • It compares the plan with performances and smoothes and coordinates ongoing movements by influencing the descending pathways. • Vermis projects to brainstem areas concerned with axial and proximal muscles. • Medial hemispheres project to brainstem areas concerned with distal limb muscles. • Neocerebellum- interacts with motor cortex in planning and programming of movements. • Cerebellum is important for learning motor activities. 2/28/2021 Cerebellum 6

Effects of Cerebella lesions. • Floculonodular lobe lesion- staggering walk in animals and children, abolition of motion sickness. • Cerebella hemisphere lesions give no signs at rest. • Hypotonia- reduced or absent muscle tone. • Atxia- in-coordination due to error in rate, range, force, and direction of movement manifesting as: 2/28/2021 Cerebellum 7

Atxia • • Drunken gait, Slurred or scanning speech, Dysmetria [past pointing], Intention tremor, Rebound phenomenon- no brakes, Adiadiadochokinsia. , Decomposition of movement. 2/28/2021 Cerebellum 8