Cerebellum
Developmental sequence of brain Fourth week Fifth week
Location of cerebellum Lies above and behind the medullar and pons and occupies posterior cranial fossa
Location of cerebellum
External structures Consists of two cerebellar hemispheres united in the midline by the vermis Primary fissure
External structures Lobules of cerebellum: Anterior lobe, posterior lobe, flocculonodular lobe. Posterolateral fissure
External structures Tonsil of cerebellum two elevated masses on inferior surface of hemispheric portion, just nearby foramen magnum Cerebellar tonsilar hernia
Internal structures Cerebellar cortex gray matter Granular layer, piriform (Purkinje) cell layer, molecular layer Cerebellar medulla white matter Superior / Middle / Inferior cerebellar peduncles Cerebellar nuclei gray matter within white matter Fastigial, globose, emboliform, dentate nuclei Interposed nucleus
Cerebellar cortex Molecular layer Piriform cell layer Granular layer White matter
Cerebellar nuclei Fastigial, globose, emboliform, dentate nuclei
Cerebellar peduncles
Cerebellar peduncles superior cerebellar peduncle (brachium conjunctivum) connects with midbrain, contain mostly efferent fibers middle cerebellar peduncle (brachium pontis) connects with pons, contain afferent fibers inferior cerebellar peduncle (restiform body) connects with medulla and with spinal cord, contain both afferent and efferent fibers
Functional divisions of cerebellum Vestibulocerebellum Archicerebellum Flocculonodular lobe Spinocerebellum Paleocerebellum Vermis and intermediate zone Cerebrocerebellum Neocerebellum Lateral zone Flocculonodular lobe Intermediate zone Vermis Lateral zone
Connections and functions of Vestibulocerebellum Connections cerebellum Afferents: receives inputs from vestibular nuclei and vestibular ganglion Efferents: projects to the vestibular nucleus vestibulospinal tract and medial longitudinal fasciculus motor neurons of anterior horn and cranial nuclei innervating extraocular muscles
Function: regulation of eyeball movements and maintenance of body equilibrium.
Spinocerebellum Connections Afferents: receives somatic sensory information via spinocerebellar tracts Efferents: Vermis projects to the fastigial nucleus vestibular nuclei and reticular formation vestibulospinal tract and reticulospinal tract motor neurons of anterior horn Intermediate zone projects to the interposed nuclei Contralateral red nucleus rubrospinal tract motor neurons of anterior horn Contralateral VL of thalamus cerebral cortex coticospinal tract motor neurons of anterior horn
Function: modulate the muscular tension.
Cerebrocerebellum Connections Afferents: receives input from the cerebral cortex via a relay in pontine nuclei Efferents: projects to dentate nucleus VL of thalamus primary motor cortex corticospinal tract motor neurons of anterior horn
Function: modulate the coordination of voluntary and fineness movement, including determination of movement strength, direction and amplitude.
Cerebellar functions Cerebellum has functions of 1. maintaining body posture, 2. controlling muscular tension, 3. coordinating of voluntary movement, but NOT initiating and performing voluntary movement.
Cerebellar injury symptoms Typical signs of cerebellar injury: a. Ataxia: incoordination of voluntary movement b. Nystagmus: tremor of eyeball c. Intention tremor Nose-to-finger test
Diencephalon
Location
Location Located between midbrain and telencephalon, mostly surrounded by cerebral hemispheres
Divisions of diencephalon (dorsal) thalamus metathalamus epithalamus subthalamus hypothalamus
External features A large egg-shaped nucleus mass, Right and left portion of thalamus are joined by interthalamic adhesion Anterior end called anterior thalamic tubercle, Posterior end called pulvinar Terminal stria Hypothalamic sulcus Dorsal thalamus
Dorsal thalamus
Subdivision Principal Nuclei Common abbreviation Ant. nuclear group Anterior Med. nuclear group dorsomedial Lat. nuclear group Dorsal layer Lateral dorsal LD Lateral posterior Pulvinar Ventral layer Ventral anterior VA Ventral lateral (intermediate) Ventral posterior Ventral posterolateral Ventral posteromedial LP VL (VI) VP VPL VPM
Functional subdivision Non-specific projecting nuclei ---- receive afferents from olfactory brain and reticular formation of brain stem (ascending reticular activating system), project to hypothalamus, corpus striatum and diffusely to cerebral cortex. Midline nuclei Intralaminar nuclei Thalamic reticular nuclei Internuncial nuclei ---- receive a wide variety of afferent fibers and in turn project widely to association areas of cerebral cortex, involved in higher nervous activity of brain. Anterior nuclear group Medial nuclear group Dorsal layer of lateral nuclear group
Functional subdivision Specific relaying nuclei Ventral anterior nucleus (VA) Ventral lateral nucleus (VL) Receive inputs from corpus striatum, dentate nucleus, and substantia nigra, project to motor cortex to regulate body movement. Ventral posteromedial nucleus (VPM) -receives trigeminal lemniscus and taste fibers Ventral posterolateral nucleus (VPL) -receives medial lemniscus and spinal lemniscus Projects to primary somatic sensory area via central thalamic radiations
Metathalamus Lateral geniculate body (LGN) Medial geniculate body (MGN) Specific relaying nuclei
Medial geniculate body (MGN) Relay station of audition Receive fibers from (brachium of) inferior colliculus Projects to auditory area via acoustic radiation Lateral geniculate body (LGN) Relay station of vision Receive fibers from retina (optic tract) Projects to visual area via optic radiation Metathalamus
Epithalamus Includes Thalamic medullary stria Habenular trigone Habenular commissure Pineal body: Melatonin posterior commissure Dorsal view
Subthalamus Ventrally to the dorsal thalamus Contains subthalamic nucleus involved in movement regulation. subthalamic nucleus
Hypothalamus Position-lies ventral to thalamus Boundaries Superior: hypothalamic sulcus Inferior: optic chiasma tuber cinereum Infundibulum (hypophysis) mamillary body Anterior: interventricular foramen Posterior: continues with midbrain tegmentum
Hypothalamus
Hypothalamic divisions Anterior to posterior Preoptic region Supraoptic region Tuberal region Mamillary region A P
Principal nuclei in hypothalamus Preoptic region: preoptic nucleus Supraoptic region Supraoptic nucleus Paraventricular nucleus produce antidiuretic hormone (ADH or vasopressin) and oxytocin Tuberal region Infundibular (Arcuate) nucleus Ventromedial nucleus Dorsomedial nucleus Mamillary region Mamillary nucleus Posterior hypothalamic nucleus
Anterior commissure Preoptic nucleus Anterior hypothalamic nucleus Supraoptic nucleus Suprachiasmatic nucleus Optic chiasma Infundibulum (stalk of the pituitary gland) Paraventricular nucleus Fornix Arcuate nucleus Pituitary gland Dorsomedial nucleus Posterior hypothalamic nucleus Lateral hypothalamic area Ventromedial nucleus Mammillary body The main hypothalamic nuclei
Hypothalamus -- connection Connects with limbic system, brainstem, spinal cord and dorsal thalamus Connects with hypophysis
Hypothalamus -- connection Supraoptic nucleus supraopticohypophysial tract posterior lobe of hypophysis (neurohypophysis) Paraventricular nucleus paraventriculohypophysial tract posterior lobe of hypophysis (neurohypophysis)
Hypothalamus -- connection Parvicellular neurons in the arcuate nucleus and nearby region secrete releasing and inhibiting hormones tuberoinfundibular tract portal vein of hypophysis anterior lobe of hypophysis
Thyroidstimulating hormone Adrenocorticot ropic hormone
Functions of hypothalamus Neuroendocrine center Subcortical higher regulatory center of the visceral activity, such as temperature regulation food ingestion reproduction fluid and electrolyte balance Regulate emotional responses and biological rhythms
Third ventricle Position: a narrow ventriclar cleft lies within diencephalon Lateral wall: dorsal thalamus and hypothalamus Communication Lateral ventricles third ventricle midbrain aqueduct fourth ventricle