Lecture 15 - Cerebellum Flashcards
1) Where is the cerebellum located and how is it connected to the rest of the brain?
2) What are the three major functions?
1) located dorsal to brainstem and is connected by three pairs of cerebellar peduncles
***receive info from proprioceptors and senses –> steady volitional movement
2) -Coordination of Mov’t = controls timing and pattern of muscle activation during mov’t
- Maintenance of Equilibrium = with vestibular system
- Regulation of Muscle Tone = meodulates spinal cord and brain stem mech involved in postural control
1) What are the 4 main dysfunctions resulting form a lesion in the cerebellum?
2) What clinical sign is not shown?
3) What real-life example did they relate cerebellar damage to?
1) -Ataxia = alters direction and extent of voluntary mov’ts, –> abnormal gait and uncoordinated muscle mov’ts
- Dysmetria = altered arnge of motion (misjudge distance) –> limbs lift too high or not high enough –> can’t touch nose cause misjudge
- Intention Tremor = oscillating motion esp of head during mov’t
- Vestibular signs = nystagmus, head tilt
2) doesn’t show weakness or paralysis of limbs
3) drunkeness
1) What are the three parts that comprise the internal organizatino of Cerebellum and describe them?
1) Cerebellar cortex = surface gray matter –> divided by sulci into folia (small folds)
2) White Matter = internal (very similar to cerebral WM)
3) Cerebellar Nuclei = three pairs deep in WM
- Fastigial (medial)
- Interpositus
Dentate (lateral)
1) Name the thhree lobes of the cerebellum.
2) Describe first lobe and what happens as a result of damage.
3) Describe 2nd lobe and what happens as a result of damage.
4) Describe last lobe and what happens as a result of damage.
1) Rostral lobe, caudal lobe, flocculonodular lobe
2) called spinocerebellum = related to spinal cord and assoc with postural tone
Damage = forelimb hyperextension and hindlimb hip flexion
3) called cerebrocerebellum
Damage = hypotonia (red muscle tone), hypermetria (ataxia - mov’ts overreach) and intenion tremor
4) called vestibulocerebellum = assoc with vestibular system and control of eye mov’t and balance
Damage = dysequilibrium, wide-based gait, nystagmus
1) What is the flocculonodular lobe made up of?
2) Where is it located in relation to other lobes?
3) How can you tell difference btw vestibulocochlear and cerebellar damange?
1) flocculus and nodulus
2) under caudal lobe
nodulus = ventromedial
flocculus = ventral and most lateral lobe on each side of cerebellum
3) additional signs with cerebellar damage in addition to shared vestibular signs –> intention tremor, dysequilibrium and problems walking up stairs
1) Name the three cerebellar peduncles
2) What does the caudal one connect with and what does it contain?
3) What does the middle one connect with and what does it contain?
4) What does the rostral one connect with and what does it contain?
1) caudal, middle and rostral cerebellar peduncles
2) connects cerebellum with Medulla –> contains Afferent AND Efferent fibers
3) connects cerebellum with Pons –> contains ONLY Afferent fibers which come from pontine nuclei (transverse pontine fibers) and ends in cerebellum
4) connects cerebellum with Midbrain –> contains predominantly Efferent fibers (carry axons OUT of cerebellum to other brain regions)
1) What is cerebellar cortex?
2) What three layers comprise it and describe them?
1) surface gray matter
2) -Molecular layer = most superficial –> axons of granule cells (parallel fibers) adn dendritic processes of Purkinje cells
- Purkinje Cell layer = middle layer –> single layer of large neuronal cell bodies (Purkinje cells)
- Granule Cell layer = deepest layer adj to WM –> predominantly small neurons called granule cells
1) What are the 5 cell types and Afferent fibers found in cerebellar cortex?
2) Describe type of cell and where they travel
1) Purkinje cells, granule cells, basket cells, climbing fibers and mossy fibers
2) Purkinje cells = ONLY OUTPUT neurons –> utilize GABA as Inhibitory NT –> inhibit neurons in deep cerebellar nuclei
Granule cells = intrinsic cells of cortex –> use glutamate as Excitatory NT –> Excite purkinje cells via parallel fibers
Basket Cells = Inhibitory interneurons –> use GABA –> inhibit purkinje cells
Climbing Fibers = arise from olivary nucleus –> end on purkinje cells –> use glutamate and aspartate as Excitatory NT
Mossy Fibers = enter cerebellum from all other sources (EXCEPT olivary nucleus) –> synapse on granule cells and excite them
1) What are the two major cerebellar inputs (axons entering)?
2) Describe climbing fiber inputs
1) climbing and mossy fiber inputs
2) arise only from olivary nucleus of caudal medulla; Excite purkinje cells (synapse)
3) Name the three mossy fiber inputs. Describe them and their path
3) -Vestibulocerebellar Fibers = come from vestibular N and nuclei –> project on flocculonodular lobe and fastigial nucleus
- helps coordinate head and eye mov’t
- Spinocerebellar Fibers = come from spinal cord (via dorsal and ventral spinocerebellar tracts) –> end in rostral lobe
- makes cerebellum aware of ongoing mov’ts via proprioceptive input from muscle spindles and joint receptors
- Cerebropontocerebellar Fibers = from pyramidal cells in cerebral cortex –> synapse on pontine nuclei –> send axons to contrallateral cerebellar cortex (via pontocerebellar fibers - form middle peduncle)
- alerts cerebellum about anticipated mov’t
1) The cerebellum monitors ongoing mov’ts to do what?
2) Where does it receive input from and via what?
3) How does it adjust for errors in mov’t?
1) to correct errors in mov’t
2) -proprioceptors –> relay info via spinal cord (spinocerebellar tracts)
- semicircular canals and utricle and saccule of inner ear (vestibulospinal fibers) –> provide info related to body or head mov’t
- cerebral cortex (cerebropontocerebellar fibers) and red nucleus –> det what the trajectory related to what ongoing mov’t should be
3) via output pathways
1) Name the 4 major cerebellar outputs. Where do they arise from?
2) Describe path of each and what they influence.
1) arise from neurons in deep cerebellar nuclei
Fastigial nucleus projections (via caudal peduncle)
Interpositus nucleus projections (via rostral peduncle)
Dentate nucleus projections (via rostral peduncle)
2) Fastigial –> vestibular nuclei and reticular formation (via vestibulospinal and reticulospinal tracts)
- influence primarily extensor muscles for maintaining posture and balance
Interpositus –> red nucleus –> rubrospinal tract
-make corrections related to gross mov’ts
Dentate –> thalamus –> output from motor cortex
-make delicate adjustments for fine, skilled mov’ts
1) What are the most important symptoms of cerebellar dysfunctino?>
2) Specific symptoms depend on what?
3) symptoms as a result of lesions occur b/c?
4) Ataxia, dysmetria and intention tremor are the result of what?
5) damage to midline portion vs localized more laterally?
1) motor-related
2) which part of cerebellum is involved and how its disrupted
3) cerebellum’s normal fn is interrupted (damage to input, output or cortex)
4) itnerference with crebellums normal role in coordination of mov’t and in maintenance of equiliubrium and appropriate muscle tone
5) damage to midline = disrupt whole-body mov’t
damage to localized more laterally = disrupt fine mov’ts of paws or limbs
1) What do cerebellar disorders result from?
1) tumors (cerebellar cystic meningioma)
2) viral infections (encephalitis, canine distemper) - may occur in utero
3) heavy metal poisoning (destroys purkinje cells)
4) genetic disorders (cerebellar disease - autorecessive)
5) trauma
1) Why may small lesions produce no or only transient symptoms?
2) Lesions of cerebellar hemispheres result in what?
3) Lesions of cerebellar vermis result in what?
4) Lesions of flocculonodular lobe (vestibule cerebellum) result in what?
1) has a relatively large margin of physiologic safety built into system –> small deficits often compensated for by other parts of brain
2) loss of muscular coordination and jerky puppet-like mov’ts of limbs (dysmetria) on ipsilateral side (same as lesion)
3) trunal tremor and gait ataxia (splayed stance and swaying of body while walking)
4) nystagmus, head tilt, tight circling and falling –> similar to damage of vestibular system
