the cerebellum Flashcards
what are the main functions of the cerebellum?
the production of coordinated movement, maintaining balance, equilibrium and posture, coordinating appropriate time, force and duration of muscle contraction or synergy, may store instructions for patterns of movements and may have linguistic and cognitive functions
how does the cerebellum act?
ipsilaterally
where is the cerebellum?
it is found under the occipital lobes of the cerebral hemispheres
what attaches the cerebellum to the brainstem?
three pairs of cerebellar peduncles
what can be seen from a)dorsal/superior b)anterior / ventral and c) inferior views of cerebellum?
a) vermis, posterior and anterior lobes
b) nodule, flocculus and the tonsils
c) tonsils
what are the subdivisions of the cerebellum?
the vestibulo/archicerebellum
the spino/paleocerebellum
the cerebro/neocerebellum
what comprises the neocerebellum?
the lateral parts of the hemispheres
what comprises the vestibulocerebellum?
the flocculonodular lobe and part of the vermis
what comprises the spinocerebellum?
the rest of the vermis and the adjacent region of the hemispheres
what is significant about the cerebellar homunculus?
it matches up to the function of the specific subdivisions
what is the role of the spino?
coordinate muscles of posture and locomotion
what is the function of cerebro?
coordinate movements of distal limbs, particularly fine, skilled and targeted movements of the hands, also involved in cognitive, linguistic and learning
what is the role of the vestibulo?
coordinating muscles involved in balance and constancy of visual fields and receiving input from the vestibular apparatus of the inner ear
regulates balance and eye movements
what is the the basis of the vestibulo
it receives ipsilateral information from balance - associated with the vestibular apparatus and nuclei and adjust muscles and eye movements in response to vestibular stimuli
where does the cerebellum receive information from and send it to?
it receives information from the vestibulocerebellar afferents from the vestibular nuclei of the same side - this is through the ICP
also through the ICP it will send information back to the vestibular nuclei through cerebellovestibular efferents
how does the vestibulo regulate eye movements?
via the vestibulospinal tract - coordinates actions of muscles that maintain equilibrium,
via the medial longitudinal fasciculus
coordinates the actions of the eye movement - this will also descend with the VST and has a similar role
where is the vestibular nucleus?
it is in the open medulla
where does information go after the vestibular nucleus?
to LMNs via the vestibulospinal tract or the neck LMNs or to III, IV, VI nerve via medial longitudinal fasciculus
cervical or lumbar cord
what vestibular nuclei are there?
the lateral and the medial in the pons level / rostral medulla
what is the function of the spinocerebellum and the basis of this?
it regulates the body and limb movements
it receives unconscious proprioception from the golgi organs and muscle spindle about the length of the muscle, level of tension and the speed of movement and adjust the muscle tone and execution of movement
which peduncles does proprioception and other sensory information travel into the cerebellum through?
the ICP - spinocerebellar tract
what is the cerebrocerebellar for?
controlling fine and targeted movements such as in the hands and also for cognitive, learning and linguistic functions
how does the cerebrocerebellar work?
it receives information on intended movements that are in progress from the cerebral cortex using the cerebropontine fibres and the olivocerebellar fibres and then ensures a smooth and orderly sequence of muscle contractions with intended precision, direction and force which is particularly important for upper limb activities
what are the connections for the cerebrocerebellum?
input from the motor cortex via the contralateral inferior olivary nucleus through the ICP (olivocerebellar afferents) and through contralateral the pontine nucleus through the MCP (pontocerebellar afferents) to the lateral hemispheres to the cerebellum
where is the entry to the spinal cord for spinocerebellar?
enters through the dorsal horn after synapsing in the dorsal root ganglion
what system is the spinocerebellum part of ?
the somatosensory
what are the afferents and efferents for the spinocerebellum?
afferents - spinocerebellar via ICP
efferents - cerebellothalamic and cerebellorubral via SCP
what is the influence of the spinocerebellum?
influences descending pathways to control muscle tone and execution of movement via the rubrospinal and corticospinal tracts
where do the efferents if the cerebrocerebellar travel?
they travel via the SCP decussation via cerebellothalamic efferents to contralateral thalamus and then to the motor cortex
what is the influence of the cerebrocerebellum?
influences descending pathways to ensure that the intended movements are precise
corticospinal tracts, corticorubral/rubrospinal or corticoreticular/reticulospinal tracts
what are the sizes of fibres entering the dorsal root?
medial divisions are large fibres and lateral are small fibres
what are the two descending pathways involved in movement?
reticulospinal - voluntary movement, consciousness and breathing
rubrospinal - controlling muscle tone
what nuclei are involved in the reticulo and rubrospinal pathways?
reticulo - reticular formation in brainstem which is the pons and the medulla
rubro - red nucleus in the midbrain
what is the result of cerebellar damage?
there are predictable movements depending on the subdivision that is damaged but this will commonly be ataxia (no order) or incoordination - person can still move but in disordered manner
what is the nucleus of the reticular formation in the medulla?
the nucleus reticularis gigantocellularis
what is truncal ataxia?
it is the inability to stand or sit without falling over due to a midline lesion affecting the vestibulocerebellum and most commonly due to medulloblastoma
describe medulloblastomas?
they most commonly occur in children in the roof of the fourth ventricle - they expand rapidly with signs of raised ICP (headache, vomiting, papilloedema and drowsiness). The tumour attacks the pathway from the vermis to the vestibular node meaning malfunction of the lateral vestibular nucleus and tract. Movements of the eye are also inaccurate. Treat with radiotherapy - very sensitive.
what is gait ataxia?
it is when the lower limbs are affected most resulting in a wide based gait and staggering. It is due to a lesion in the spinocerebellum and is most common in chronic alcoholics due to degeneration of the cerebellar neurons in paravermal areas. There is pronounced shrinkages of the cortex in the anterior lobe. Head tremor and sensory ataxia are usually present.
what is the result of lesions in the cerebrocerebellum?
incoordination of voluntary movements particularly in the upper limb - many causes that can be degenerative, trauma or vascular. The patients present with tremor of intent, adiadochokinesia, dysarthria and past point or dysmetria
adiadochokinesia?
inability to perform rapid alternating movements
dysmetria?
cannot coordinate movements - overshoot or under
dysarthria?
slow or slurred speech
impaired phonation or articulation
