Lecture 18 Flashcards
Identify inputs to the cerebellum
-pontocerebellar fibers
-Spinocerebellar pathways: Dorsal spinocerebellar tract, cuneocerebellar tract
-vestibular inputs
Describe pontocerebellar fiber inputs to cerebellum
-copy of descending motor commands sent from:
-cortical motor area to pontine nuclei (cortico-pontine fibers)
-Then axons from pontine nuclei (pontocerebellar fibers- at pons level) cross the midline and enter the cerebellum through middle cerebellar peduncles
-copy sent from cortex to contralateral cerebellum
Describe spinocerebellar inputs to cerebellum
-cerebellum receives info from ipsilateral side of body
-afferent copy (feedback) from sensory receptors carried from:
-two tracts: cuneocerebellar tract and dorsal cerebellar tract
-similar to PCML pathways- info from sensory receptors through through SC to caudal medulla- cross midline to contal thalamus and cortex
-nucleus dorsalis of clark= nucleus gracilis
-external cuneate nucleus= cuneate nucleus
Describe cuneo-cerebellar and dorsal spinal-cerebellar tracts
-cuneocerebllar tract carrying info from arms and upper trunk, corollary of cunetus facisculus
-dorsal spinal cerebellar tract corollary of fascicus gracilis from leg and lower body
-Like primatry sensory neuron pathways that synapse on second order sensory neurons of nucleus cutanatus or nucleus gracilis, branches of sensory info from primary sensory neurons of spino-cerebellar pathways synapse on second order sensory neurons
-Cuneocerebellar pathways- synapses on external cuneate nucleus, lateral to cuneate nucleus in caudal medulla. Some of fibers coming up through fasiculus cunateus coming to nucleus cuneatus and from there to contra thalamus/somatosensory cortex. Have some branches once at caudal medulla that go to external cuneate nucleus (copy). From there ascend through rest of the brainstem and enter into cerebellum - spinal equivent of nucelus cunateus of PCML . Axons then enter ipsi cerebellum via inferior cerebellar peduncle
-Some fibers going to nucleus gracilis in caudal medulla via fasciculus gracilis cross midline to contralatral thalamus/cortex, and other fibers for dorsal spinal cerebellar tract go to nucleus dorsalis of clark (found in intermediate zone of spinal cord spanning multiple segments)- spinal equivent of nucleus gracilis for PCML pathway. Axons out to lateral column of white matter of spinal cord and traverse through SC and brainstem and into ipsi cerebellum via inferior cerebellar peduncle.
Describe how vestibular info comes into the cerebellum (3rd input to cerebellum)
- vestibular info coming in through 2 different pathways:
- primary vestibular sensory neurons (info from hair cells of semicircular canals and otiliths via vestibulo-cochlear nerve) go to vestibular nuclei, also have branches that go directly into cerebellum on ipsilateral side. Received direct vestibular information from periphery on ipsi side
- Vestibular nuceli in pons and medulla have pathways that also project to cerebellum
- Both pathways go into cerebellum on ipsilateral side via inferior cerebellar peduncle (speciofically subsection called juxarestiform body)
Describe dentate nucleus outputs from the cerebellum
-From lateral region/hemisphere axons into deep cerebellar nuclei via dendate nuclei, processes info further- cell bodies out of cerebellum via superior cerebellar peduncle, cross in midbrain, carried to contralateral thalamus and synapse on thalamic nuclei and project to regions of the cortex
-other pathways synapse on contralateral red nucleus- feedback back to region of cerebellum for motor learning
-function of lateral region- motor planning/learning to higher level areas such as pre motor cortex, supplementary motor area, primary motor cortex, parietal cortex
Describe interposed nuclei outputs from cerebellum
-From intermediate region- projects to interposed nuclei
-first output- axons out of cerebellum via superior cerebellar peduncle, cross at midbrain to thalamus and cortex on contralateral side, specifically pre motor cortex, SMA, motor cortex- influences distal limbs via lateral corticospinal tracts (ipsi)
-Other pathways from interposed nucleus to red nucleus, cross midline to nucelus on contra side- influences arms (ipsi) via RST
-Responsible for online corrdination of movement (updating), correction of movements of LCST and RST
Describe outputs from fastigial and vestibular nuclei from cerebellum
-vermis region projects to fastigial nuclei, from fastigial nuclei exit superior cerebellar peduncle cross at midbrain to contra thalamus to motor region of cortex for neck/trunk muscles (axial muscles)- influences bilateral muscles via anterior corticospinal tract
-fastigial nuclei also project to other brainstem nuclei includuing vestibular nuclei and reticular formation (bilaterally)- influences balance/tone, coordinates activity of vestibulospinal tracts, control vestibular reflexes and reticular reflexes
-projections from inferior vermis and flocculonodular lobe to vestibular nuclei (ipsi), axons directly to vestibular nuclei on ipsilateral side, strong reciprical connections and interactions with vestibular system and cerebellum- influences balance and eye movement
Describe somatotopic organisation of
-Found in vermis and intermediate zone, little in lateral zone (responsible for learningf/planning than coordination)
-Have two somatotopic organisations, one in anterior lobe and one in post
-in anterior lobe- flipped upside down, head inferior, arms and legs superior, body, trunk and neck found in vermis (midline),
arms and legs in intermediate zone
-post lobe, upright, head superior, arms and legs inferior, in this zone somatotopic organisation only found in intermediate zone not vermis
Describe functions of lateral hemishphere
motor planning and learning, for extremities
Describe functions of intermediate hemisphere
-distal limb coordination, arms/hands, legs/feet
Describe functions of vermis and flocculonodular lobe
-proximal limb and trunk coordination (trunk and neck)
-balance and vestibulo-oculo reflexes
Describe cerebellum role as a comparator
-receives:
1.Copy of efferent information= corollary dischange, reecives copy of motro commands
2.Receives ascending information= external feedback from sensory systems, ongoing ascending info (prop, touch, vest info)
-Compares intended goal of movement to the actual motor response and projects back to motor areas for corrections
Describe the double crossover
-LCST right cortecx influences left spinal cord, muscle on contra side, copy sent to contra cerebellum
-cerebellum recives sensory info on ipsi side to contra thalamus/cortex
-symptoms on same side of lesion, cerebellum assessing movements on ipsi side
