Cerebellum Flashcards
Function of the Cerebellum
- coordinates movement by influencing timing and force of contractions of voluntary muscles
- involved in motor planning and motor learning
- adjusts posture
- Plays a role in eye movements, balance, locomotion, learning
Compares actual motor output w/ intended movement (from frontal lobe) and then adjusts as necessary
What does the cerebellum not do
- is not primary in sensory function
- with damage one can still feel
- is not primary in motor function
- with damage one is not paralyzed or weak
Integration in the cerebellum
once information arrives at the cerebellum
- sent to the cerebellar cortex
- cerebellar cortex sends input to deep cerebellar nuclei
- information sent back out to affect CNS and periphery
- information coming to the cerebellum includes that coming from the cerebral cortex
Inputs to the cerebellum
- Cerebral cortex => pontine nuclei on contralateral side
- vestibular system ispilaterally
- spinal cord ipsilaterally
- proprioceptors (to SC) ipsilaterally
Outputs from the cerebellum
- brainstem
- spinal cord
- cerebral cortex
- red nucleus (midbrain)
- thalamus
cerebral output is vital for normal movement
projections to thalamus are motor these outputs then project to motor areas of cerebral cortex
What is the rule of three in the cerebellum
- three lobes
- three vertical sections
- three layers of the cerebullar cortex
- three functional movement divisions
- three pairs of deep nuceli
- three pairs of peduncles
What are the three lobes of the cerebellum
- anterior
- posterior
- flocculonodular lobe
anterior lobe
- superiorly
- seperated from posterior lobe by primary fissue
Posterior lobe
- inferior
- cerebellar tonsils
- clinically = increased intracranial pressure can force tonsils into foramen magnum
- therefore compressing vital brainstem structures that regulate breathing and cardiovascular activty
flocculonodular lobe
- tucked under posterior lobe
3 vertical sections of the cerebellum
- midline vermis: medial
- intermediate zone of paravermis
- lateral hemisphere
Vertical section
midline vermis:
- medial
- posture and trunk ataxia
- eye movement abnormalities
- accompanies by vertigo nausea and vomitin
when lesion occurs
vertical sections
intermediate zone of paravermis
- proprioceptive sensory information to correct movement error
vertical sections
lateral hemisphere
- limb control ataxia
What are the functional movement divisions
- Vestibulocerebeullum: regulates equilibrium, balance and eye movement
- Spinocerebellum: coordinates gross limb movement
- Cerebrocerebellum: coordinates precise, distal voluntary movement
3 layers of the cerebellar cortex
- outer neurons: inhibitory
- purkinje cell bodies: inhibitory damage = disinhibition of movement
- inner: interneurons, mossy fibers, climbing fibers
Mossy fibers
- input fibers
- originate in spinal cord and brainstem
- convey somatosensory arousal, equilibrium and cerebral cortex information to cerebellum
- stimulate release of cortical motor pathways
Climbing fibers
- input fibers
- from inferior olivary nucleus in medulla
- conveys information reguarding movement error to cerebellum,
- active in learning new movement (excitatory)
3 pairs of deep cerebellar nuclei
- main influence on other motor centers
- receive excitatory input from mossy and climbing fibers
- receive inhibitory input from purkinje cells
- Types medial to lateral: Fastigial, interposed (globose and emboliform), and dentate
- each vertical section projects to specific cerebellar nuceli or vestibular nuceli
Fastigal nuclei
- part of vestiularcerebellum (regulates equilibrium
- ex: reaching to a high shlef; provides anticipatory contraction of the LE and back muscles to prevent balacne loss
- sends information to vestibular nuclei
- important for balance and eye movement
Interposed nuclei
- part of spinocerebellum - coordinates gross limb movement
- sends information to reticular formation red nucleus and thalamus
- motor learning/planning and limb movements
Dentate nucleus
- part of cerebrocerebellum - coordinates distal limb movements
- sends information to motor and premotor cortex
- motor planning and locomotion
Cerebellar peduncles
carry information between cerebellum and brainstem
- inferior cerebellar peduncle: from medulla (afferenet and efferent)
- middle cerebellar peduncle: from pons (afferent only)
- superior cerebellar peduncle: from midbrain, efferent only
Integration of motor and sensory information
- cerebellum gets input and sends information from contralateral cortex and ispilateral body
- cerebellar stroke: unilateral lesions affect SAME side of body
- coordination of voluntary movement via influence on corticospinal and cotricobranstem tracts
Causes of cerebellar damage
- cerebral vascular accident
- multiple sclerosis
- tumor
- trauma
- degnerative disease
- alcoholism (anterior lobe)
Cerebellar damage
- impacts voluntary coordinated movement
- rate
- range
- force
Common signs of cerebellar damage
- ataxia
- dysmetria: inability to accurately move intended distance
- dysdiadochokinesia: inability to rapidly alternate movements
- hypotonia
- intention tremor
- postural instability and gait disturbance
- dysarthria
effects of cerebellar damage
on locomotion
- increased postural sway
- excessive or diminished responses to pertubrations
- abnormal oscillations of the trunk
- gait ataxia
- decomposition of movement: maintaining a fixed position of one joint while other is moving decreased smoothness
effects of damage
to vestibulocerebellum on locomation
- head tilt
- horizontal nystagmus: eye “twitiches” horizontally
- circling away from and falling toward side of lesion
- gait ataxia
effects of damage to posterior vermis on
locomotion
- common cause: tumor in fourth ventricle
- gait ataxia without limb ataxia - marked deficit in tandem gait
- may be able to reach, kick, and perform unilateral stance
effects of damage to anterior lobe
on locomotion
- common cause: atrophy due to alcoholism
- begins in anterior vermis and intermediate portions of anterior lobe
- gait ataxia
- unable to preform unilateral stance
- ataxia with heel-to-shin test
- deficits in reaching and speech as disease progresses posteriorly
Cerebellum and medial lesions vs lateral
- somatotrophic representation
- medial lesions: dizziness and eye movemetns
- lateral = limbs
Pathology of anterior lobe
- multiple sclerosis
- friedreich’s ataxia: hereditary spinal ataxia
cerebellar disorders
- paraneoplastic syndrome: somthing that looks like cerebellum in nature but there is actually a dormit cancer that could develop – often lung cancer
- arnold chiari malformation
