Cerebellum Flashcards
Main cerebellar function
Coordinating movements
Maintaining posture
Procedural memory
Organization of cerebellar gray matter
Molecular layer- lays next to pial surface and has few neurons. Contains basket and stellate cells
Purkinje layer- contains purkinje cells
Granular layer- deep later with granule cells and a few golgi cells
White matter- axons
Purkinje cells
Efferents-Output from cerebellar cortex
Inhibitory to deep cerebellar and vestibular nuclei
Use GABA
Granule cells
Smallest neurons, only excitatory neurons in cerebellum
Use glutamate
Stellate cells
Their axons synapse only with purkinje cells and inhibit them
Start shaped stellate dendrites
Golgi cells
Inhibitory neurons
Use GABA
Large scattered neurons with short axons
Basket cells
Their axons synapse with purkinje cells and inhibit them
Use GABA
Climbing fibers
Cerebellar afferent fibers originating in inferior olive
Myelinated with excitatory influence on purkinje cells
Convey info regarding movement errors to the cerebellum
Mossy fibers
Afferent cerebellar fibers originating from spinal cord, reticular formation, vestibular system and pontine nuclei
Synapse with granulocytes
Convey somatosensory, arousal, equilibrium and cerebral cortex motor info to cerebellum so that we can do the proper movement that we’re intending to do
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 the head and body
Some purkinje fibers leave and go straight to vestibular nuclei and some stop at fastigial nuclei
Spinocerebellum
Functional name for vermis and paravermal region
Somatosensory info, internal feedback from spinal interneurons and sensorimotor cortex
Functions to control ongoing movement via the brainstem descending tracts
-Axial and LE movements, gait and station
Pontocerebellum or neocerebellum or cerebrocerebellum
Located in lateral hemispheres of cerebellum
Input from cerebral cortex (premotor, sensorimotor, and others) via pontine nuclei
Functions in coordination of voluntary movements, planning of movements and timing
Fibers leave via perkinje fibers
Afferents enter the cerebellum via
Cerebellar peduncles
Afferents entering from vestibular system
Vestibular nuclei and cranial nerve VIII via mossy fibers
Enter via inferior cerebellar peduncle (juxtarestiform body)
Afferents entering from spinal cord
Anterior spinocerebellar tract - leg info
Posterior spinocerebellar tract- leg info (keim wants us to pay attention to this one)
Cuneocerebellar tract- arm info (pay attention to this one as well)
All via mossy fibers
Entering via inferior cerebellar peduncle
Afferents entering from cerebral cortex
Cortico-pontocerebellar via mossy fibers
Cortico-olivocerebellar via climbing fibers
Cortico-reticulocerebellar via mossy fibers
Enter from middle cerebellar peduncle
Posterior spinocerebellar tract
Axons carrying unconscious proprioceptive info from lower limb
1st order neurons enter via DRG and ascends in gracile fasciculus- synapse in dorsal nucleus of Clarke (gray matter from C8-L2)
2nd order neurons ascend in dorsolateral funiculus (posterior spinocerebellar tract)
Enter cerebellum via inferior cerebellar peduncle (restiform body)
Cuneocerebellar tract
Axons carrying unconscious proprioceptive info from upper limb
1st order neurons enter via DRG and ascends in cuneate fasciculus- synapses in accessory (lateral) cuneate nucleus in lower medulla
2nd order neurons from accessory cuneate nucleus ascends to cerebellum and enters via the inferior cerebellar peduncle (restiform body)
Superior cerebellar peduncle
Major efferent route from the globose, emboliform and dentate nuclei
Afferent fibers from ventral spinocerebellar tract run here too
Middle cerebellar peduncle
Largest peduncle
Afferent fibers from pontine nuclei relayed to cortex
Inferior cerebellar peduncle
Primarily afferent pathways from spinal cord
Cerebrocerebellum
Precise, coordinated movements of extremities, mainly UE
Fastigial nuclei
Receives info from spinocerebellum and vestibulocerebellum
Sends efferents to pontine and medullary reticular formation which then affects reticulospinal tracts and helps with posture
Also sends efferents to vestibular nuclei which then affects vestibulospinal tracts
Dentate nucleus
Receives info from cerebrocerebellum via purkinje fibers Sends efferents (leaving through superior cerebellar peduncle) to red nucleus (affect rubrospinal tract and flexion of upper limbs) and thalamus
Globose and emboliform nuclei (interposed nuclei)
Receives info from spinocerebellum via perkinje fibers
Sends efferents to red nucleus and thalamus
Also sends fibers to inferior olivary nucleus which then sends fibers back to cerebellum- this system is very important for correcting movement errors
Unilateral lesions of cerebellum
Affects ipsilateral side (because cerebellar fibers cross to opposite cerebral cortex and then corticospinal tracts cross back over to the original side)
Ataxia - common to all lesions of cerebellum
Ataxia is a voluntary, normal strength, jerky and inaccurate movements not associated with hyperstiffnes
Presents as wide gate and guarding- sometimes called drunken sailor gate
Lesion of vestibulocerebellum
Nystagmus
Truncal ataxia- difficulty maintaining sitting and standing balance
Truncal instability (titubation-hips will move back and forth or head moves back and forth like saying no) - cant tandem walk (one foot in front of other)
Results in midline ataxia
Lesions of spinocerebellum
Gait and truncal ataxia- wide base, staggering base
Results in midline ataxia
Midline ataxia
Truncal instability
Titubation
Gate ataxia
Lesion of cerebrocerebellum
Dysarthria- slurred poorly articulated speech
Ataxic gate- staggering ataxic gate with tendency to fall forward side of lesion
Appendicular ataxia
Decomposition of movements
Limb ataxia manifestations:
Dysdiadochokinesia- inability to rapidly alternate movements
Dysmetria- inability to accurately move an intended distance
Action tremor- shaking of the limb during voluntary movement
Appendicular ataxia
Cerebrocerebellar problems
Ataxia of speech
Hypotonia
Decomposition of movement
Dysmetria- inability to move intended distances
Dysdiadochokinesia-difficulty performing rapidly alternating movements
Cerebellar ataxia vs sensory ataxia
Cerebellar ataxia:
Positive rombergs test
Unable to stand with feet together eyes open or closed
Normal vibratory sense, proprioception and ankle reflexes
Sensory ataxia:
Can stand with feet together with eyes open, but not closed (Romberg test)
Abnormal vibratory sense, proprioception and ankle reflexes
Exam of vestibulocerebellum and spinocerebellum
Station
Walking
Tandem gait
Exam of cerebrocerebellum
Rapid alternating movements Finger to nose Toe to finger Heel to shin Rebound and check reflex Speech
