The Cerebellum

1. The Cerebellum DR. S. H. KHAN

2. Position • Lies behind the fourth ventricle, medulla and pons • Occupies posterior cranial fossa • Largest part of Hind brain • Coordinates voluntary movements of the body Cerebellum

3. External features Consists of twocerebellar hemispheres united in the midline by the vermis Vermis Hemisphere Superior view Inferior view

5. External features Tonsil of cerebellum two elevated masses on inferior surface of hemispheral portion just nearby foramen magnum Tonsil

6. Fissures & Lobes • Two deep fissures • Primary fissure • Posterolateral fissure • Three lobes • Flocculonodular lobe flocculus and nodule • Anterior lobe • Middle lobe (Posterior lobe) Corpus of cerebellar

7. Fissures & Lobes Anterior lobe corpus of cerebellar Primary fissure Middle lobe Flocculonodular lobe Posterolateral fissure

9. Internal structures Gray matter • Cerebellar cortex • Intracerebellar nuclei (embedded in white matter) • Dentate nucleus • Fastigial nucleus • Interposed nucleus • Emboliform nucleus • Globose nucleus White matter • medullary center

10. Internal structures Fastigial nucleus Cerebellar cortex Globose nucleus Dentate nucleus Emboliform nucleus medullary center

11. Three functional divisions • Archicerebellum • Flocculonodular lobe • Lingula of vermis • Paleocerebellum • Vermis and • intermediate zone • Neocerebellum • Lateral zone Intermediate zone Vermis Lateral zone Flocculonodular lobe

12. Functions of Cerebellum • Controls the same side of the body • Regulates and coordinates voluntary movements of the body • Keep the movements smooth, balanced and accurate • Planning of sequential movement • Controls muscle tone, posture and equilibrium

13. Injury : Cerebellar syndrome • Hypotonia • Postural changes & alteration of Gait • Ataxia(disturbance of voluntary movements) Intention tremor • Dysdiadochokinesia ( inability to perform alternating movements regularly & rapidly) • Nystagmus (abnormal movements of eyeballs) • Dysarthria (disorder of speech)

14. Connections of cerebellum • Cerebellum is connected to the brainstem by 3 paired bundles of nerve fibers ( Peduncle) Three peduncles • Inferior cerebellar peduncle －connect with medulla and spinal cord, －contain both afferent and efferent fibers • Middle cerebellar peduncle －connect with pons, －contain afferent fibers • Superior cerebellar peduncle －connect with midbrain, －contain mostly efferent fibers

15. The Diencephalon

16. Diencephalon “between brain”

17. Position of Diencephalon • Position: Lies between midbrian and cerebrum, almost entirely surrounded by cerebral hemisphere

18. Subdivisions of Diencephalon • Thalamus (Dorsal thalamus) • Metathalamus • Epithalamus • Subthalamus (Ventral thalamus) • Hypothalamus

19. Dorsal thalamus interthalamic adhesion External features • A large egg-shaped nucleus (mass of gray matter) • Situated in the lateral wall of 3rd ventricle and in the floor of the lateral ventricle • Anterior end called anterior thalamic tubercle, • Posterior end called pulvinar • The right & left thalami are joined by interthalamic adhesion

21. Structure of Thalamus • White matter －Stratum zonale- thin layer covers the superior surface －External medullary lamina- covers the lateral surface －Internal medullary lamina- Y shaped vertical sheet, divides the gray matter into 3 parts • Gray matter －Anterior thalamic nuclei － Medial thalamic nuclei － Lateral thalamic nuclei － Intralaminar nuclei

22. Subdivision of dorsal thalamus Three main parts －divided by internal medullary lamina (Y) • Anterior part (Anterior nuclear group) • Medial part (Medial nuclear group) • Lateral part (Lateral nuclear group) Int. medullary lamina Ant part Med. part Lat. part

24. internal medullary lamina Med. nuclear group Lat. posterior Ant. nuclear group Lat. dorsal Pulvinar Ventral anterior Medial geniculate body (MGN) Ventral intermediate Ventral posterior nucleus (VP) Lateralgeniculate body (LGN) Ventral posterolateral (VPL) Ventral posteromedial (VPM )

25. Function of Thalamus • Great integrating center for sensory impulses • Receives sensory information of all types, except smell • Receives profuse connections from all parts of cerebral cortex, cerebellum and corpus striatum. • Receives exteroceptive (pain, temp. touch), proprioceptive (muscles, joints) and visceral informations Injury • Sensory loss • Thalamic syndrome

26. Metathalamus • Lies posteroinferior to thalamus • Consists of medial geniculate body lateral geniculate body

27. Metathalamus Lateralgeniculate body (LGN) Medial geniculate body (MGN) Metathalamus

28. Metathalamus • Medial geniculate body (MGN) • Relay station of audition • Receive fibers from inferior colliculus • Projects to auditory area via acoustic radiation • Lateralgeniculate body(LGN) • Relay station of vision • Receive fibers from optic tract • Projects to visual area via optic radiation

29. Epithalamus Includes • Thalamic medullary stria • Habenular nucleus • Habenular trigone • Habenular commissure • Pineal body • posterior commissure Pineal body

30. Subthalamus • Situated between thalamus and midbrain • Contain subthalamic nucleus, parts of red nucleus and substantia nigra

31. Position－lies below the thalamus Forms the floor & inf. Part of lat. Wall of third ventricle Boundaries Superiorly: hypothalamic sulcus Inferiorly: optic chiasma tuber cinereum Infundibulum mamillary body Anterior: lamina terminalis Posterior: continues with midbrain tegmentum Lateral : internal capsule Hypothalamus

33. hypothalamic sulcus optic chiasma lamina terminalis mamillary body Infundibulum

34. Subdivisions • Preoptic region • Optic region • Tuberal region • Mamillary region

35. Important nuclei • Optic region • Supraoptic nucleus -produce antidiuretic hormone (ADH/ vasopressin ) • Paraventricular nucleus- produce oxytocin • Tuberal region • Infundibular nucleus • Ventromedial nucleus • Dorsomedial nucleus • Mamillary region • Mamillary nucleus • Posterior hypothalamic nucleus

36. Paraventricular nucleus Paraventriculohypophyeal tract Supraoptic nucleus Mamillary nucleus Supraopticohypophyseal tract arcuate nucleus tuberoinfundibular tract Infundibulum of pituitary anterior lobe of hypophsis posterior lobe of hypophysis

37. Hypothalamus --connection • Connects with limbic system • Connects with brainstem and spinal cord • Connects with dorsal thalamus • Connects with hypophysis

38. Hypothalamus --connection • Supraoptic nucleus supraoptic nucleus (ADH) →supraopticohypophyseal tract →posterior lobe of hypophysis • Paraventricular nucleus paraventicular nucleus (oxytocin) →paraventriculohypophyseal tract→posterior lobe of hypophysis

39. Paraventricular nucleus Paraventriculohypophyseal tract Supraoptic nucleus Supraopticohypophyseal tract Inferior hypophyseal a. posterior lobe of hypophysis Hypophyseal v.

40. Hypothalamus Function • Regulates functions of neuro-endocrine system －Secrets ADH & Oxytocine, which then transported to posterior pituitary gland by nervous stimulation －By forming Releasing/ Inhibitory hormones, controls Ant. Pituitary gland to secret hormones ( through minute vessels of Hypothalamic-Hypophyseal system) • Autonomic nervous system －Controls CVS, Respiratory, Alimentary functions

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