Cerebellum Flashcards
What are the functions of the cerebellum?
Coordinating movements, maintaining posture, motor learning, and procedural memory
What is the molecular layer of the cerebellum?
Lies next to pial surface and has a few neurons; cell bodies of basket cells and stellate cells are there
What is the purkinje layer of the cerebellum?
Contains purkinje cell bodies
What is the granular layer of the cerebellum?
Deepest layer; contains granule cells and a few golgi cells
What is the white matter of the cerebellum?
Axons of neurons
What are purkinje cells?
Output cells from cerebellar cortex; inhibit the cerebellar nuclei and the vestibular nuclei; neurotransmitter is GABA; highly differentiated with many dendrites
What are granule cells?
Smallest neurons; only excitatory neurons; neurotransmitter is glutamate
What are stellate cells?
Their axons synapse only with purkinje cells and inhibit them; star-shaped dendrites
What are golgi cells?
Inhibitory neurons; neurotransmitter is GABA; large scattered neurons with short axons
What are basket cells?
Their axons synapse with purkinje cells and inhibit them; neurotransmitter is GABA
What are the types of afferent fibers in the cerebellum?
Climbing and mossy fibers
What are climbing fibers?
From inferior olive; myelinated with excitatory influence on purkinje cells; convey info regarding movement errors to the cerebellum
What are mossy fibers?
From spinal cord, reticular formation, vestibular system, and pontine nuclei; synapse with granulocytes; convey somatosensory, arousal, equilibrium, and cerebral cortex motor info to cerebellum
What are the functional divisions of the cerebellum?
Archicerebellum/vestibulocerebellum, paleocerebellum/spinocerebellum, and neocerebellum/pontocerebellum
What is the vestibulocerebellum?
Functional name for flocculonodular lobe; receives info directly from vestibular receptors; sends output to the vestibular nuclei; also receives info from visual areas; functions to influence eye movements and postural muscles of head and body
What is the spinocerebellum?
Functional name for vermis and paraventral region; somatosensory info, internal feedback from spinal interneurons and sensorimotor cortex; functions to control ongoing movement via the brainstem descending tracts; axial and lower extremity movements as well as gait and station
What is the pontocerebellum?
Input from cerebral cortex (premotor, sensorimotor, and others) via pontine nuclei; functions in coordination of voluntary movements, planning of movements, and timing (mainly upper extremity)
What are the afferent pathways entering the cerebellum?
Vestibular system (vestibular nuclei, cranial nerve VIII), anterior/posterior spinocerebellar tract, cuneocerebellar tract, cortico-pontocerebellar, cortico-olivocerebellar, and cortico-reticulocerebellar tracts
What axons are in the posterior spinocerebellar tract?
Axons carrying unconscious proprioception from lower limb
What axons are in the cuneocerebellar tract?
Axons carrying unconscious proprioception from upper limb
Describe the superior cerebellar peduncle
Major efferent route from the globose, emboliform, and dentate nuceli; afferent fibers from ventral spinocerebellar tract run here too
Describe the middle cerebellar peduncle
Largest peduncle; afferent fibers from pontine nuclei relayed to cortex
Describe the inferior cerebellar peduncle
Primarily afferent pathways from spinal cord
What nuclei are considered deep nuclei?
Fastigial, globose, emboliform, and dentate
Describe ataxia as it relates to the cerebellum
Common to all lesions of cerebellum; voluntary, normal strength, jerky, and inaccurate movements not associated with hyperstiffness
Unilateral lesions in the cerebellum affect the _________ side
Ipsilateral
What do lesions of the vestibulocerebellum (connections between vestibular system and flocculonodular lobe) cause?
Nystagmus, truncal ataxia (difficulty maintaining sitting and standing balance), and truncal instability (titubation, can’t tandem walk)
What do lesions in the spinocerebellum cause?
This is where connections between the cutaneous and proprioceptive information coming from the spinal cord to the vermis and paravermis regions; causes gait and truncal ataxia (wide base, staggering base)
What are midline ataxias? Give examples
Ataxic syndromes caused by vestibulocerebellar and spinocerebellar disease; truncal instability and equilibratory (gait) ataxias
What is truncal instability (titubation)?
Tremor of the trunk in an anterior-posterior plane at 3-4 Hz
What is equilibratory (gait) ataxia?
Wide based, irregular steps with lateral veering
What do lesions of the cerebrocerebellum cause?
Dysarthria (slurred, poorly articulated speech), ataxic gait, decomposition of movements
How do limb ataxias manifest?
Dysdiadochokinesia, dysmetria, and action tremors
What is dysdiadochokinesia?
Inability to rapidly alternate movements
What is dysmetria?
Inability to accurately move an intended distance
What is an action tremor?
Shaking of the limb during voluntary movement
What do you find in someone with appendicular ataxia?
Hypotonia, decompositon of movement, dysmetria (inability to accurately move an intended distance), and dysdiadochokinesia
Compare and contrast cerebellar ataxia and sensory ataxia
Cerebellar: romberg test positive, unable to stand with feet together with or without eyes open, normal vibratory sense, proprioception and ankle reflexes
Sensory: can stand with feet together with eyes open, but not closed (positive romberg test) but abnormal vibratory sense, proprioception, and ankle reflexes
What exams/observations should you make when examining the vestibulocerebellum and spinocerebellum?
Station, walking, tandem gait
What exams/observations should you make when examining the cerebrocerebellum?
Rapid alternating movements, finger-to-nose, toe-to-finger, heel-to-shin, rebound and check reflex, and speech
