Caudate Nucleus Strength Of Movement

Neuro tutoring Block 7 Week 2 1. How are the cells of the cerebellum organized into layers? • • • • •

Pia Molecular- purkinje dendrites, basket, stellate cells **Purkinje- purkinje cell bodies Granular- granule cells, golgi cells White

2. What are the 5 cell types of the cerebellum and their functions, connections, and neurotransmitters? • • • • •

Purkinje (large): GABA (-) (inhibitory) to deep cerebellar nuclei. Dendrite tree radiates perpendicular to folia. Granule: Glu (only excitatory) smallest, one axon can excite many purkinje fibers, parallel to folia axis. Golgi: GABA (-) to granule cells. Interneurons. Basket: GABA potent (-) of purkinje Stellate: GABA (-) of purkinje

Spinal Cord/Cortex/red nucleus/cerebellum contralateral Inf. Olivary nuc (ION)  climbing fibers  (+)  purkinje  (-)  deep nuclei  output Moss fibers  (+)  granule cells  (+)  parallel fibers  purkinje Golgi  (-)  granule cells Basket and stellate cells (-)  purkinje 3. What are the functions and pathways associated with the following structures? -flocculonodular lobe: eye movement (VOR) and balance • vestibulocerbellum: vestibular input from mossy fibers -vermis: postural adjustments • spinocerebellum: get input from mechanoreceptors (trunk and neck). Controls axial/trunk and proximal limb movement. -intermediate zone: input from neck, trunk, limbs • spinocerebellum: distal limb movement -lateral zone: movement planning and initiation and learning • cerebrocerebellum: major input from cortex and pons -inferior cerebellar peduncle: restiform body • afferents from spinal cord and brainstem (spinocerebellar)

-middle cerebellar peduncle: branchium pontis; largest; cerbrocerebellar afferents; cortex  pons  cerebrocerebellum -superior cerebellar peduncle: brachium conjuntivum; mainly efferents from deep nuclei to thalamus, red nuclei, descending tracts 4. How would you describe the locations and functions of the 4 deep cerebellar nuclei? • Dentate: largest, most lateral • Emboli form/Globose: interposed nuclei • Fastigial: most medial; more vermal inputs • **All outputs are excitatory except to ION (GABA) 5. What are the main functions of the cerebellum and its associated tracts? Function: modulates descending tracts: movement and posture, motor learning compares intention with actual movement, and compensates for errors -lateral zone: -intermediate zone: -vermis: -flocculonodular lobe: -corticopntocerebellar: movement planning -ventral spinocerebellar: monitoring descending and peripheral information regarding movement -dorsal spinocerebellar: cerebellum gets feedback from periphery during movement -dentarubrospinothalamic: adjusts motor output 6. What are the 2 types of afferent fibers to the cerebellum? • 1) climbing fibers: o Innervate purkinje (1 climbing fiber per purkinje) o Form contralateral ION (+) purkinje dendrites in molecular layer o Complex spike: 1-3 spikes/sec (know what it looks like) may also modulate mossy fiber input • 2) Mossy fiber: o Excite granule cells (2 purkinje) o Will excite multiple dendrites o Simple spike- up to 200/sec 7. Describe the main afferent and efferent pathways of the cerebellum: • 5 afferents o 1) Vestibulonuclei juxtarestiform body vestibulocerebellum (floculonodular body)



Reciprocal connections control eye movements and body equilibrium while standing or moving

o 2) Ipsilateral spinal cord/lower medulla/contralateral ION (Dorsal) restiform body spinocerebellum (vermis and int.) o 3) Contralateral spinal cord (ventral)  superior cerebellar peduncle contralateral spinocerebellum (vermis and int. zone) 

cross twice end up ipsilateral

o 4) Contralateral cortex  pontine nuclei  middle peduncle (brachium pontis)  cerebrocerebellum (lateral) o 5) Monoaminergic fibers: from brainstem   •

raphe nuclei  5HT (serotonin) locus cerelus  NE (noradrenergic)

4 Major Efferents: all exit via superior cerebellar peduncle o 1) flocculonodular vestibular nuclei o 2) vermis: ongoing movement control  Vermis  (-)  fastigial nuclei  (+)  brainstem medial descending tracts proximal limb and axial  Vermis  (-)  fastigial nuclei  (+) motor nuclei of thalamus  motor and premotor cortex o 3) Int. Zone: ongoing movement control of distal limbs  Interposed nuclei  red nuclei  lateral descending tracts  distal limb  Interposed nuclei  thalamus  motor and premotor cortex  corticospinal tract distal limb o 4) Lateral Zone: Initiation, planning, timing of voluntary movements  Crosses 2 times so you get ipsilateral loss with lesion  Dentorubrspinothalamic tract: • Dentate corticopontine tract  lateral zone • Dentate corticospinal tract  spinal cord • Dentate red nucleus  thalamus  motor/premotor cortex

8. Symptoms of cerebellar dysfunction: • 1) appendicular ataxia: agonist and antagonist aren’t coordinated; ipsilateral • 2) dysdiadechkinesia: difficulty with rapid alternating movements; ipsilateral • 3) Titubation: can’t maintain upright posture (trunk muscles); lesion to vermis/floculonodular • 4) Gait Imbalance: leg ataxia and impaired VOR suppression • 5) Impaired VOR suppression: eyes following moving objects will be jerky; vermis isn’t allowing proper VOR suppression • 6) Scanning Dysanthmia: clipped words; hesitation between syllables • 7) decreased muscle tone, decreased reflexes: because cerebellar input via deep nuclei is primarily excitatory

9. What are some potential causes of cerebellar disorders? • Ischemic stroke/hemorrhagic stroke • Tumor • Infection • Atrophy: etOH, affects legs >>> arms (medial cerebellum) 10. What are the components of the basal ganglia? • Striatum: GABA o Caudate nucleus: cognitive function, less motor involvement o Putamen: motor function • Globus Pallidus: GABA o GPe, GPi • STN (Subthalamic Nucleus): Glu • Substantia Nigra o SNc- pars compacta: dorsal and dopaminergic (DA) o SNr- pars reticulata: ventral (GABA) • Nucleus acumbens: connects caudate to putamen (DA) • GPi and SNr are final output of basal ganglia • Corpus striatum: putamen, caudate, GP • Lentiform 11. Describe the direct and indirect pathways of the basal ganglia:

12. What are the general functions of the basal ganglia? • Regulate movement • Influence descending motor tracts • Control eye movements • Memory orientation in space • Contributes to cognition (caudate) MD and prefrontal cortex • Limbic function • Final Test Question: All of the following control eye movement except.... 13. What are some symptoms of basal ganglia dysfunction? • NT problem • Abnormal motor/movements: releasing motor cortex from inhibition • Resting tremor: pill rolling (Parkinsons) • Athetosis: striated lesion • Hemiballismus: STN lesion; contralateral • Dystonia: abnormal posture • Bradykinesia: slow movements 14. Describe the lesion and its associated symptoms in the following basal ganglia disorders: -Huntington disease • Bilateral atrophy of caudate due to increased CAG repeats on chromosome 4 • Autosomal dominant • Hyperkinesias from lesion to indirect pathway • Chorea, athetosis (excess movement) • Memory loss, cognitive dysfunction, psych disturbance -Parkinsons disease • Direct pathway lesion: lose DA neurons at SNc • Bradykinesia • Hypophonic voice • Mask-like facial expression • Tardive dyskinesia: from L-Dopa treatment; involuntary face and tongue movement -hemiballismus • Indirect path lesion; excess movement

-stereotactic surgery • 1) Pallidotomy: lesion of GPi in indirect pathway, trying to induce hyperkinesias to correct for bradykinesia and rigidity o Most dramatic effect; contralateral • 2) Thalamatomy: lesion thalamus in direct pathway, stops movement induction; use: treat severe tremor • 3) Deep brain stimulation: inhibit STN with high frequency stimulation; use to treat bradykinesia and rigidity (inhibit indirect pathway) o Has contralateral effects 15. Cerebellum Output to spinal cord

Direct No direct output

Basal Ganglia None (input is cortical and thalamic) No direct output

Connections with brainstem

Brainstem connections

Less: SNc/SNr

Cortical connections

Indirect via pons

Direct cortical

Thalamic projections

Yes

Yes

Output

Excitatory

Function

Coordinate movement execution; compare intention with actual

Lesions

Ipsilateral symptoms

Inhibitory (through indirect) Disinhibitory (through direct) *via thalamus Planning and execution of complex motor strategies; amplitude, velocity, and strength of movement Contralateral of bilateral symptoms

Symptoms of lesions

Intentional tremor, ataxia, impaired balance

Input from spinal cord

Resting tremor, hypokinesia (Parkinsons)/hyperkinesias (Huntingtons)