1. Ruther Armand R. Martinez, MD

2. Gross Appearance It is the largest part of the hindbrain and lies posterior to the fourth ventricle, the pons and the medulla oblongata.

3. Gross Appearance It is divided into 2 symmetric hemispheres joined by a narrow median vermis.

4. Gross Appearance It is separated from the occipital lobe by the tentorium cerebelli. A thinner midline portion- the vermis External surface- folia

5. Gross Appearance It is connected to the posterior aspect of the brainstem by 3 symmetrical bundles of nerve fibers called the superior, middle, and inferior cerebellar peduncles.

6. Divisions It is divided into 3 main lobes; the anterior lobe, middle lobe, and flocculonodular lobe.

7. The anterior lobe is on the superior surface and is separated from the middle lobe by the primary fissure. Involved with propulsive, stereotyped movements.

8. The middle lobe is the largest and situated between the primary and uvulonodular fissures. It is concerned with the coordination of fine movement.

9. The flocculonodular lobe is situated posterior to the uvulonodular fissure. It is concerned with equilibrium and connects with the vestibular system.

10. Cerebellar Peduncles The cerebellum is linked to other parts of the CNS by numerous efferent and afferent fibers that are grouped together on each side into three large bundles.

11. Cerebellar Peduncles 3 pairs located above and around the 4 th ventricle, attach to the cerebellum to the brain stem and contain pathways to and from the brain tem.

12. Cerebellar Peduncles The inferior cerebellar peduncle contains fiber systems from the spinal cord and lower brainstem.

13. Cerebellar Peduncles The middle cerebellar peduncle consists of fibers from the contralateral pontine nuclei.

14. Cerebellar Peduncles The superior cerebellar peduncle, contains axons that send impulses to both the thalamus and the spinal cord, with relays in the red nuclei.

15. Afferents to the Cerebellum Primarily carried via the inferior and middle cerebellar peduncles. End in either climbing fibers or mossy fibers in the cerebellar cortex.

16. Afferents to the Cerebellum Climbing fibers originate in the inferior olivary nucleus and synapse on purkinje cell dendrites.

17. Afferents to the Cerebellum Mossy fibers are formed by afferent axons from the pontine nuclei, spinal cord, vestibular nuclei, and reticular formation. They synapse with granule cell dendrites.

18. Cerebellar Cortex It is a large sheet with folds lying in the coronal or transverse plane. Each fold contains a core of white matter covered superficially by gray matter.

19. Cerebellar Cortex The gray matter may be divided into 3 layers; Molecular layer- external Purkinje cell layer- middle Granular layer- internal

20. Cerebellar Cortex Consists of 5 primary cell types; Granule cells Purkinje cells Basket cells Golgi cells Stellate cells

21. Molecular layer contains 2 types of neurons; Stellate cell-outer Basket cell-inner These cells give rise to inhibitory synapses on Purkinje cells.

22. The Purkinje cells are large Golgi type I neurons. Cell bodies in the Purkinje cell layer and dendrites fan out in a single plane to the molecular layer. They form inhibitory synapses.

23. Granule cells are the only excitatory neurons in the cerebellar cortex. They send their axons into the molecular layer to become the parallel fibers.

24. Excitatory and Inhibitory Effects Excitation Mossy fibers  granule cell Climbing fibers  Purkinje cell Granule cell  Purkinje cell Granule cell  golgi cell Granule cell  basket cell Granule cell  stellate cell Inhibition Basket cell  Purkinje cell body Stellate cell  Purkinje cell dendrite Golgi cell  granule cell Purkinje cell  roof nuclei Purkinje cell  lateral vestibular nuclei Purkinje cell  Purkinje cells Purkinje cell  golgi cell

25. Intracerebellar Nuclei 4 masses of gray matter are embedded in the white matter of the cerebellum; Dentate-largest Emboliform-medial to the dentate Globose-medial to emboliform Fastigial-near the midline in the vermis

26. Intracerebellar Nuclei Neurons in these intracerebellar nuclei project out of the cerebellum and thus represent the major efferent pathway from the cerebellum.

27. Intracerebellar Nuclei Cells receive inhibitory input from Purkinje cells. They also receive excitatory inputs from outside the cerebellum.

28. Efferents from the Cerebellum Efferents from the intracerebellar nuclei project via the superior cerebellar peduncle to the contralateral red nucleus and thalamic nuclei.

29. Efferents from the Cerebellum Each cerebellar hemisphere regulates coordination and muscle tone on the ipsilateral side of the body.

30. Functions of the Cerebellum It coordinates skilled voluntary movements by influencing muscle activity. Controls equilibrium and muscle tone through connections with the vestibular system and the spinal cord and its gamma motor neurons.

31. Good Morning!