9/22 Cerebellum (Mandel) Flashcards
Be able to recognize and define the functions of Cerebellum
Coordination, balance, posture, eye movements, corrects motor error (smooths), motor learning.
Be able to locate and identify the deep cerebellar nuclei and their connections cerebellar connections
- Dentate, emboliform, fastigial, and globose. Receive excitatory projections from mossy and climbing fibers. GABAergic input from purkinje cells. Major output for cerebellum. Communicate together and with cortex and brain. Flocculonodular lobe sends output to vestibular nuclei instead.
- Dentate is deep within lateral hemispheres, also where input is from; fastigial within vermis, afferents from vermis; interposed in intermedial paravermal zone inputs from paravermis. Fastigial to Vestibular N., Pontine and medullary FR via ICP, Interposed to red n. via SCP, dentate to VL and Red n. via SCP.
Be able to identify and define the functions of the vestibulocerebellum
• Vestibulocerebellum: Archicerebellum. Input from vestibular nuclei, auditory and visual sensory input. Direct and secondary vestibular inputs, position of head and body in space (superior colliculus). Fastigial efferents to vestibular and p/m reticular nuclei bilaterally. Vestibulospinal and reticulospinal for posture, balance. Efferents to CN III, IV, VI from vestibular nuclei (Eye)
• Main cerebellar input pathways (Dorsal, cuneocerebellar, ventral, climbing, vestibular, ponto)
- Dorsal spinocerebellar tract: input leg proprioceptors, through nuc. dorsalis of clark (eyes of Pikachu) to inferior CP
- Cuneocerebellar: arm proprioceptors, external cuneate n. (sensory dec) ICP
- Ventral Spinocerebellar: Leg interneurons, spinal cord neurons, superior CP.
- Climbing fibers: red nuc/cortex/brainstem/spinal cord, inferior olivary n. ICP No lesion specific to this.
- Vestibular: vestibular system, vestibular ganglia and nuclei, Juxtarestiform body.
- Pontocerebellar fibers: cortex, pontine nuclei, middle CP. Crosses immediately
Describe input to cerebellum
- From frontal/parietal cortex through the pons—main input (corticopontine tract). Synapses in pontine nuc and forms middle cerebellar peduncle. Synapses in lateral hemispheres of cortex.
- From inferior olive through inferior cerebellar peduncle to all of cerebellar cortex. Crosses immediately in the medulla.
- From spinal cord through ICP to intermediate and vermis. Proprioception
- From vestibular nucleus. Through ICP to intermediate zone and floccularmodular lobe.
Topography of cerebellar cortical efferents (where nuc. are located).
• Medial to lateral pattern: lateral hemisphere to dentate, intermediate zone to interposed nuclei (globose and emobiform), vermis and flocculonodular lobe to fastigial nucleus (flocc skips vestigial to fastigial directly)
Be able to recognize, define, and list the internal cellular organization of the cerebellum
- Granule cell layer: Input layer. Granule cells and a few large golgi interneurons. Mossy fibers terminate here. Glutamatergic
- Purkinje cell layer: output layer. Single sheet of purkinje cells. Extend into molecular layer where they receive inputs from climbing fibers and neurons. Project to deep nuclei where GABA is released
- Molecular layer: outermost. Processing for cerebellar cortex. Cell bodies and dendrites of inhibitory interneurons (stellate and basket). Dendrites of purkinje.
- 5x as many neurons as cerebral cortex.
- Granule cells receive mossy fiber input: mossy fibers are main input axonal type
- Massive parallel fiber input, from granule cells, onto dendritic tree of Purkinje cells
- Climbing fibers like ivy around Purkinje cells from inferior olive
- Inhibitory interneurons to modulate the excitation of Purkinje cells
- Only Purkinje cells project out of cerebellar cortex – to Deep Cerebellar Nuclei
Be able to identify the neurotransmitters of the listed neurons of the cerebellum
• Climbing fiber (inputs from olive): excitatory. Mossy Fibers inputs: excitatory. Golgi cells: inhibitory. Purkinje axon outputs via deep nuclei: inhibitory
Be able to define Mossy fibers and climbing fibers and identify their origins
- These are the two main afferent fibers. Both excitatory. Mossy fibers originate from cell bodies in the spinal cord and brain stem and carry sensory information from periphery and cerebral cortex. Synapse on dendrites of granule cells in granular layer. Each cell receives inputs from a few mossy fibers but info distribution is wide.
- Climbing fibers originate in inferior olivary n. and convey sensory information to cerebellum from periphery and cerebral cortex. Wraps around cell bodies and dendrites of purkinje, numerous synaptic contacts (each contacts 1-10 purkinje but each purkinje receives input from one climbing). Arranged topographically.
Be able to recall the symptoms of cerebellar abnormalities and describe their laterality
- Hypotonia: diminished resistance to passive limb displacements. Related to pendular reflexes (after leg jerk, leg oscillates before rest)
- Astasia: loss of ability to maintain a steady limb or body posture.
- Abasia: loss of ability to maintain upright stance.
- Ataxia: abnormal execution of multi-jointed voluntary movements. Ipsilateral to lesion. Midline lesions of vermis of flocculonodular lobes unsteady gait and eye movement abnormalities. Lateral lesions ataxia of limbs. Purkinje neurodegeneration
- intention tremor: result of a series of erroneous corrections in movement.
- Dystonia: no pathology for cerebellum. Disruptions along CTS and CTC.
• All deficits from cerebellar lesions occur on the ____ side of the body
• Ipsilateral
The cerebellum contributes only ____of the total volume of the brain but contains more than ____ of its neurons
• 10%; ½
Deficits are of_______; not involved in _______
• Motor functions; sensory experiences
• Describe efferent connections of the cerebellum
cerebelloreticular, corticonuclear, cerebellothalamic, cerebellorubial
- Cerebellovestibular tract: output from cerebellum to extensor muscles of axial muscles (tone and adjustment)
- Cerebelloreticular tract: information to motor circuits of brain stem
- Corticonuclear tract: cerebral cortex to brainstem motor function of oculomotor nerve
- Cerebellothalamic tract: superior cerebellar peduncle, decussates to terminate in ventral anterior n of thalamus
- Cerebellorubial tract: information from cerebellum to motor systems of brainstem
Be able to identify and define the functions of the spinocerebellum
Spinocerebellum: Also Paleocerebellum. Lobes near midline. Proprioceptive input from dorsal column pathway of spinal cord, trigeminal nerve, visual and auditory systems, and spinocerebellar tract. Output to deep cerebellar nuclei which project to cerebral cortex and brain stem. Modifies activity of descending motor pathways. Spinal, brainstem input informing cerebellum of limb position/proprioception, and motion. Fastigial nucleus for vestibulospinal and reticulospinal pathways (axial musculature). Interposed nuclei to red nucleus for rubrospinal and ventrolateral thalamus for corticospinal (both limb musculature)
