2.5 Flashcards
Function of the cerebellum
Coordinate movement
Maintain posture, balance, and muscle tone
Learning of motor tasks
Process memory of skilled motor activity
Morphology of the cerebellum
2 hemispheres
Vermis
Sulci
Peduncles
Horizontal fissure
Arbor vitae
Grey matter of the cerebellum
- Cerebellar cortex: just like that of the cerebellar cortex; an outer layer of grey matter
- Deep cerebellar nuclei: collections of grey matter embedded in the white matter of the cerebellum
Layers of grey matter
Three layers contain more neurons than the cerebral cortex
Purkinje cells
Form the middle layer of the cerebellar cortex
Terminate on 2 nuclei:
- deep cerebellar nuclei
- vestibular nuclei (balance)
White matter of the cerebellum
Contains:
- afferent (sensory) and efferent (motor) fibers
- association fibers: local fibers which arise from cerebellar Purkinje cells and project to other areas of the cerebellum
Where do cerebellar nuclei receive afferents from?
Fastigial nucleus
- vestibular system
Interposed nuclei
- spinal cord
Dentate nucleus
- cerebrum and pons
Cerebellar lobes and their connections
Flocculonodular - vestibular system
Anterior - spinal cord
Posterior - cerebral cortex
Superior cerebellar peduncle
Principally carries cerebellar signals to midbrain and thalamus
Pathway: efferent from cerebellar cortex and deep nuclei
Middle cerebellar peduncle
Carries signals from pons to the cerebellum
Pathway: afferent transverse fibers of the pons
Inferior cerebellar peduncle
Connects the cerebellum with the medulla oblongata and spinal cord
Pathway: afferent from spinal cord and brainstem nuclei
Communication of the cerebellum
Afferents, efferents, and intrinsic fibers
Afferents of the cerebellum
Afferents come from:
- vestibular system
- cerebral cortex
- spinal cord
- deep brain structures
These afferents go to the cerebellar cortex and the deep cerebellar nuclei via inferior and middle peduncles.
Efferents of the cerebellum
Efferents come from:
- Purkinje cells (inhibitory)
- deep cerebellar nuclei
Purkinje cells to vestibular nuclei: bilateral
Efferents via the inferior cerebellar peduncles: bilateral posture and balance
Efferents to the superior cerebellar peduncle: decussate to their target areas and contribute to the corticospinal tract.
- damage causes ipsilateral symptoms
Cerebellar connections
Midline: vermal: trunkal muscles
Lateral: hemispheric: limb muscles
The cerebellum processes information from..
the ipsilateral body and contralateral cerebral cortex
Which sensory systems give input to the cerebellum?
The specialized receptors, muscle spindles, and Golgi tendon organs (GTOs), unique to muscles and tendons, respectively, collect and send sensory information about the position and movement of the body’s parts to the cerebellum via the ascending sensory pathways to the cerebellum
What other structures send input to the cerebellum?
Motor cortex - about impending and desired movements
Visual system - helps the cerebellum to aim movement in the desired direction
Auditory system - auditory guidance of movement
Vestibular system - orientation and motion of head, so that it can continuously make corrections to maintain or regain balance
Where does the cerebellum primarily send output?
thalamus
What are the main sources of cerebellar afferents?
The vestibular system (vestibular ganglion and nuclei), which terminates in the vestibulocerebellum.
The spinal cord, which terminates in the spinocerebellum.
The cerebral cortex, mostly via the corticopontocerebellar pathway but also via the corticoreticulocerebellar and cortico-oliveocerebellar pathways, all of thich terminate in the cerebrocerebellum.
What is the name given most afferents? Are they excitatory or inhibitory?
Mossy fibers
They are excitatory and release glutamate
They arise from the vestibular system, spinal cord, and cerebral cortex via the brainstem
A lesion of the cerebellum results in symptoms that appear on the ___ side of the body.
ipsilateral (same)
What is the result of a lesion of the cerebellum?
Abnormal execution of a motor task and not deficits in motor function such as paralysis or paresis
Hypotonia - decreased muscle tone
Ataxia - uncoordinated movement; other parts of the brain may “take over” and compensate for any cerebellar deficits
Flocculonodular syndrome
Characterized by the inability to maintain equilibrium and truncal ataxia, unsteady walking, swaying from side to side, tendency to fall. The individual appears inebriated. May experience nystagmus. Symptoms may be bilateral.
Disorders following a lesion in the vermal and paravermal zones
Results in abnormal stance and gait with feet -positioned far apart, providing a compensatory broad base and unable to walk in tandem
Exhibits titubation (rhythmic tremor) of the trunk or head when sitting or standing, and postural changes of the head, in which the head may be held in a rotated position or tilted towards one side
- The side in which the head is rotated or tilted may not be a reflection of the side of the lesion
Abnormal eye movement such as spontaneous nystagmus, that occurs without stimulation of the vestibular apparatus
Disorders following lesions in the hemispheric zone
Exhibited primarily as ataxia and tremor on the ipsilateral side of the body
Abnormal cerebellar output to the motor cortex via the thalamus, resulting in an abnormal execution of voluntary movement mediated by the corticospinal and corticorubral-rubrospinal tracts
