Cerebellum Flashcards
What are the outputs of the vermal cerebellum?
- Through the fastigial nucleus sends information to the vestibular nucleus and pontine reticular formation (bilaterally)
- From here information descends in medial descending system through lateral vestibulospinal tract and pontine reticulospinal tract
- Some neurons of flocculo-nodular lobe send axons directly to cells of vestibular nuclei
- Together the efferent vermal information suggests a role in equilibrium and posture
Describe the anatomic divisions of the cerebellum.
The cerebellum is anatomically divided into the two hemispheres, the midline vermis and the flocculonodulus.
What are the functions of each cerebellar “lobe”?
The hemispheres are involved in appendicular control, the vermis is involved in axial control, and the flocculonodular lobe is involved in vestibular balance.
What is the afferent fiber from the inferior olives? Through which peduncle does it reach the cerebellum?
The afferent fiber from the inferior olives is the climbing fiber. It enters the cerebellum through the inferior cerebellar peduncle.
What is Mollaret’s triangle?
Mollaret’s triangle is a physiologic connection between the red nucleus, inferior olives, and dentate nucleus of the cerebellum. A lesion in this pathway can cause palatal myoclonus.
What are the deep nuclei of the cerebellum (medial to lateral)?
Medial to lateral, the cerebellar deep nuclei are fastigial, globus, emboliform, and dentate.
What are the common abbreviations for axonal tracts within the cerebellum signaling pathways?
SCP, Superior cerebellar peduncle; MCP, middle cerebellar peduncle; ICP, inferior cerebellar peduncle; DRT, dentatorubrothalamic; VSC, ventral spinocerebellar; CPC, corticopontocerebellar; SC, spinocerebellar; VC, vestibulocerebellar; LVS, lateral vestibulospinal; MLF, medial longitudinal fasciculus.
What are the three cerebellar peduncles? Which carry efferent/afferent fibers? Where are they seen in cross section? What tracts course through them?
Superior (SCP) Midbrain DRT and VSC Middle (MCP) Pons CPC Inferior (ICP) Medulla All other tracts to/from the cerebellum (mostly inferior olive, all are climbing fibers) *DRT, dentatorubrothalamic; *VSC - ventral spinocerebellar; *CPC - corticopontocerebellar;
Where does information go from the paravermal cerebellum?
- Through the interposed nuclei
- To the contralateral red nucleus (primarily)
- Directing motor output through the rubrospinal tract, part of the lateral descending system
Where does the lateral hemispheric cerebellum send it’s information
- Through the dentate nucleus
- To the contralateral ventrolateral thalamus (VL) primarily
- Influences wide areas of the cortex, particularly primary motor and associated motor cortex
Where does vestibular input to the cerebellum occur?
- Arrives in the flocculo-nodular lobe
* Limited extent nearby regions of the posterior lobe
Information from the spinal cord enters the cerebellum where?
- Distributed to the vermal and paramerval portions
- Double somatotopic distribution is found (anterior and posterior lobe both)
- Axial body surface found medially, distal limbs projecting laterally
What information is contained in the lateral zone of the cerebellum?
• Lateral zone does not receive any direct primary afferent input
• Vast amounts of information come to cerebellum from the cortex by way of pontine nuclei to end in the lateral zone
• Arises from primary motor cortex and associated motor cortex
• Contains collaterals of corticospinal and corticobulbar fibers
○ Corticobulbar has fibers that terminate in the medulla
• Cortical input is from contralateral cortex (at the level of the lateral zone of cerebellum)
○ From a synapse with ipsilateral neurons in the basal pons and pontine neurons send axons contralaterally to cerebellar hemispheres
What are the 4 functional regions of the cerebellum given in class?
• Vestibulocerebellum • Spinocerebellum ○ Two subdivisions ○ Vermis and paravermal contributions • Cerebrocerebellum
What are the principal inputs of the 4 functional regions?
• Vestibulocerebellum ○ Vestibular sensory cells • Spinocerebellum (vermis) ○ Visual, auditory, vestibular, somatosensory • Spinocerebellum (paravermis) ○ Spinal afferents • Cerebrocerebellum ○ Cortical afferents
What are the functions of the 4 functional areas of the cerebellum?
• Vestibulocerebellum ○ axial control, vestibular reflex Balance, eye movement • Spinocerebellum (vermis) ○ axial motor control, posture, locomotion, gaze • Spinocerebellum (paravermis) ○ distal motor control • Cerebrocerebellum ○ initiation, planning, timing
What are the principal destinations of the 4 functional areas of the cerebellum?
• Vestibulocerebellum ○ axial motoneurons • Spinocerebellum (vermis) ○medial systems • Spinocerebellum (paravermis) ○ lateral system Red nucleus • Cerebrocerebellum ○ integration areas (thalamus)
What are the main characteristics of cerebellar deficits?
- Disturbances of synergy, equilibrium or tone
- Always ipsilateral
- Cerebellum communicates with ipsilateral side of body, contralateral motor cortex
- Cerebellar lesions result in a loss of coordination (including equilibrium)
- NO loss of muscle strength or sensation
- Lesions of modest amounts of cerebellar cortex have little obvious motor effect and to do so must involve large regions of cortex or lesions of the underlying deep nuclei
What is ataxia?
• Loss of synergy and loss of coordination or timing of the involved muscles
• Looks like past-pointing (dysmetria)
• Inability to bring a limb to a required or desired point in space
• Decomposition of movement or (dysdiadochokinesia)
• Often intention tremors perpendicular to the direction of the limb motion
○ Inappropriate coordination of antagonist muscles
• Extraocular problems
○ Inappropriate nystagmus
○ Slurred speech
What is the helpful pneumonic for recognizing cerebellar deficits?
• HANDS Tremor • H - hypotonia ○ Anterior lobe injury • A - ataxia ○ Dysdiadochokinesia (impaired rapid alternating movements) ○ Decomposition of movement ○ Dysmetria (past-pointing) • N - Nystagmus • D - Dysarthria • S - stance and gait problems • Tremor - intention tremor, oscillation as limb approaches a target
What types of cells are located in each of the cerebellar layers?
The molecular layer contains (1) stellate cells, (2) basket cells, (3) dendrites of Purkinje cells, (4) dendrites of Golgi type II cells, and (5) axons of granule cells.
The Purkinje layer contains the cell bodies of Purkinje cells.
The granular layer contains (6) granule cells, (7) Golgi type II cells, and (8) glomeruli (synaptic complexes that contain mossy fibers, axons and dendrites of Golgi type II cells, and dendrites of granule cells).
What are the three layers of the cerebellar cortex?
- Outermost molecular cell layer
- Middle Purkinje cell layer
- Innermost granular cell layer
What type of fiber originating in the cerebellar cortex is inhibitory on the deep cerebellar nuclei?
Purkinje fibers originate in the cerebellar cortex and synapse on the deep nuclei as an inhibitory neuron
Where does the dentatorubrothalamic tract synapse?
These fibers synapse in the ventrolateral (VL) nucleus of the thalamus before ascending to the cortex.
- dentate nucleus
- red nucleus
- thalamus
