Cerebellum Flashcards
Sketch the functional subdivisions of the cerebellar cortex; label the flocculonodular lobe, the vermis and the paravermal zones of the spinocerebellum and the lateral pontocerebellar zones of the cerebellar hemispheres.
anatomy wise, cerebellum consists of the vermis, two adjacent cerebellar hemispheres, and a nodule; 3 cell layers of cerebellar cortex are granule, purkinje, and molecular; afferent axons terminate in cortex; 4 deep cerebellar nuclei in the medullary substance, where efferent axons from cortex terminate, project to CNS; floculonodular lobe is the most inferior part of vermis with adjacent cortex
functional: vestibulocerebellum is the floculonodular lobe, spinocerebellum is the middle (vermis and paravermal), pontocerebellum consists of lateral lobes
List the afferent connections to the: (1) vestibulocerebellum; (2) spinocerebellum; and (3) pontocerebellum. To each afferent connection add: (i) the origin of the pathway; (ii) which cerebellar peduncle the pathway enters the cerebellum; and (iii) whether the pathway projects to the ipsilateral or contralateral cerebellum.
1) primary fibers of vestibular nerve and secondary fibers of vestibular nuclei project to ipsilateral vestibulocerebellum via ICP
2) posterior spinocerebellar tract (PSCT) is uncrossed, carries propioception (muscle spindle and GTR), originates in dorsal nucleus of clarke, via ICP; cuneocerebellar tract is the upper limb equivalent of PSCT, uncrossed tract from accessory cuneate nucleus of medulla, via ICP; anterior spinocerebellar tract originates in gray mtter of lumbar and sacral spinal cord, carries integrated (whole limb) proprioception, crosses twice (@ spinal entry and through SCP); spino-reticulo-cerebellar pathways originates from nuclei in reticular formation, uncrossed, ICP; trigeminocerebellar fibers from 3 sensory nuclei of CN5 (principal sensory via MCP, spinal V via ICP, mesencephalic nucleus via SCP (proprioception of jaw)) and are all uncrossed
3) pontocerebellar fibers: arise from pontine nuclei, the corticopontine tract is uncrossed but the axons of the pontine nuclei crosses at midline and enters MCP;
4) jack of all trades: olivocerebellar fibers originate at inferior olivary complex (which gets input from vestibular nuclei, spinal cord), relays vestibular info to vestibulocerebellum and motor feedback data to spinocerebellum, relays info from red nuclei (from cerebral cortex) to pontocerebellum, cross and enter ICP, terminates as climbing fibers
Sketch the cytoarchitecture of the cerebellar cortex to indicate: (1) the excitatory and inhibitory neurons in each layer of the cortex and the connections between them; (2) the origin and distinct cellular targets of mossy and climbing fiber afferents; (3) the components of a cerebellar glomerulus. Trace how the organization of the cerebellar cortex leads to the direct or indirect stimulation of Purkinje cells by mossy or climbing fiber afferents.
1) granule cell layer is deepest of 3 layers of cerebellar cortex, mossy fibers epsp on granule cells and deep cerebellar nuclei; granule cells ascend as parallel fibers which epsp purkinje cells and all inhibitory interneurons (golgi cells, outer stellate cells and basket cells); golgi cells ipsp granule cells of cerebellar glomeruli
purkinje cells layer: big purkinje cells, their axons are the only output (efferent) of cerebellar cortex, their axons are GABA ergic on deep cerebellar nuclei and vestibular nuclei
molecular cell layer: has basket and stellate cells, climbing fibers (olivocerebellar tract) are 1 to 1 with purkinje cells and are very excitatory, parallel fibers excite golgi cells, stellate cells, basket cells, and purkinje cells; both basket and stellate inhibit purkinje cells
2) see above
3) a mossy cell axon terminal, granule cell, and golgi cell axon terminal are enclosed by a glial cell and form a cerebellar glomerulus
List the efferent pathways from the: (1) vestibulocerebellum; (2) vermal spinocerebellum; (3) paravermal spinocerebellum; and (4) pontocerebellum. To each efferent pathway add: (i) the location of the Purkinje cell source; (ii) the identity of deep cerebellar nuclei involved; (iii) which cerebellar peduncle the efferent pathway exits the cerebellum; (iv) the identity and location of target nuclei.
1) vestibulocerebellum is the only part whose purkinje cells send axons outside cerebellum (to vestibular nuclei), also outputs ipsilaterally to all 4 vestibular nuclei, via ICP, targets vestibulospinal tract
vermal pway: purkinje to fastigial nuclei, bilaterally via ICP to the vestibular nuclei and reticular formation for posture and walking
paravermal pway: to globose and emboliform nuclei, leave SPC and cross in midbrain to contralateral red nucleus and thalamic nucleus to primary motor cortex and motor planning cortex to control fine movement of side ipsilateral to cerebellum
pontocerebellum sends from purkinje to dentate nucleus, via SCP to contralateral red nuc and thalamus to cortex, does motor planning
List the general functional properties of efferent pathways from the: (1) vestibulocerebellum; (2) vermal spinocerebellum; (3) paravermal spinocerebellum; and (4) pontocerebellum. The list should include (i) the motor pathways (tracts) influenced/activated by each pathway; and (ii) whether the pathway influences movement on the ipsilateral, contralateral or both sides of the head and/or body.
vestibulospinal: control of eye movement and neck movement,
vermal does righting reflex and walking, axial control, bilateral
paravermal and pontocerebellar do fine motor movement, but paravermal is more about correcting ongoing movement while pontocerebellar is about motor planning, both ipsilateral
List the clinical signs associated with lesions of the: (1) vestibulocerebellum; (2) vermal spinocerebellum; and (3) cerebellar hemispheres. Explain why none of these lesions results in paralysis.
1) often damaged in medulloblastoma, ataxic gait, head tremor, nystagmus
2 alcoholic degeneration, walking dysfunction
3 intention tremor, dysmetria (error in distance of movements), dysarthria (inability to enunciate speech)
what side does a part of the cerebellum coordinate movements for?
ipsilateral
what ascending fiber type are all afferent axons to the cerebellum?
they’re all mossy fibers except for olivocerebellar which are climbing fibers
what are the four pairs of deep cerebellar nuclei?
fastigial, globose, emboliform, and dentate (biggest one)
