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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)

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-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)

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Reciprocal connections control eye movements and body equilibrium while standing ormoving

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 andpremotor 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 arent coordinated; ipsilateral

2) dysdiadechkinesia: difficulty with rapid alternating movements; ipsilateral

3) Titubation: cant 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 isnt 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

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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 involvemento 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:

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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

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-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 Basal Ganglia

Input from spinal cord

Direct

None (input is cortical and

thalamic)

Output to spinal cord No direct output No direct output

Connections with brainstem Brainstem connections Less: SNc/SNr

Cortical connections Indirect via pons Direct cortical

Thalamic projections Yes Yes

Output Excitatory Inhibitory (through indirect)Disinhibitory (through direct)

*via thalamus

Function Coordinate movement execution;compare intention with actual

Planning and execution of complexmotor strategies; amplitude,

velocity, and strength of movement

Lesions Ipsilateral symptoms Contralateral of bilateral symptoms

Symptoms of lesions Intentional tremor, ataxia, impaired

balance

Resting tremor, hypokinesia

(Parkinsons)/hyperkinesias

(Huntingtons)