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Neurology lab#6 April 12-4-2011 بسم هللا الرحمن الرحيم The cerebellum █ External structure:Consists of two cerebellar hemisphere united in the midline by the vermis █ Internal structure : Gray mater consisting in▼ {1}cerebllar cortex {2} ceremllar nuclei Dentate nuclei Fastigial nuclei Emboliform nucli Globose nucli ▼White mater █ Cerebellum structurally divided into 1-ant.lobe 2-post.lobe 3-flocculonodular 1 █ note befor:☻ afferen fibers Toward cerebellum which mean the cerebellum receive them ☻Efferent fibber: away from cerebellum which mean cerebellum project them ☻ always any injure in cerebllum lead to ipsilateral effect because tract away and toward Cerebllum walk ipsilateral or make 2crossing so the net is ipsilatral ☻No direct effect of cerebellum on the lower motor neurons thus cerebellum Affect On the body movement via affecting on the origin of the descending tract which terminate at lower motor neurons █Cerebellum functionally divided Into: (1)-vestibulocerebllum: ☻ Floculo-nodular lobe ☻ it receives afferent fibers from vestibular nuclei of vestibular nerve in brain stem and inner ear ☻it project efferent fiber to vestibular nuclei ln brain stem → 2 - vestibulospinal tract → motor neurons of anterior horn ☼☼you notice that vestibular nuclei project and receives fibers from cerebllum ☻Function: involved in eye movements and maintain balance ☼☼as you know vestibulospinal tract in the origion is ipsilatral (2)-spinocerebllum: ☻vermis and intermediate zone ☻it receives afferent fiber{sensory input} via spinocerebellar tracts{ant and post spinocerebllum tracts} - ☻it project efferent fibers from -A- vermis to the fastigial nucleus in cerebllum → vestibular nuclei in brain stem → vestibulospinal tract → motor neurons of anterior horn {fastigial vestibular pathway} -B- vermis to the fastigial nucleus → reticular formation in brain stem → 3 reticulospinal tract → motor neurons of anterior horn{ Fastigeal reticular pathway} -C-intermedeat zone to interposed nuclei{ Globose and emboliform in cerebllum}then to Contralateral red nucleus in brain stem → rubrospinal tract →motor neurons of anterior horn{ Globoseemboliform-rubral pathway} ☼☼You notice that from the interposed nuclei to red nuclei {1crossing}+rubrospinal tract{1crossing}so 2 crossing ☻Function: play an important role in control of muscle tone and coordination of muscle movement on the same side of the body (3)- Cerebrocerebellum ☻latral zone : ☻it receives afferent fibers from the cerebral cortex via a relay in pontine nuclei(corticopontocerebellar pathway)which mean that these 4 fibers come from cortex of cerebrum then relay in nuclei of pons then go to cerbllum ☻ It project efferent fibers to dentate nucleus → contralateral thalamus → primary motor cortex → corticospinal tract → motor neurons of anterior horn ☼☼You notice that from dentate nucleus to contralatral thalamus {1crossing}+corticospinal tract{1crossing}so 2crossing ☼☼other ex about afferent fiber which cerebellum receive them in cerebrocerebellum ◄ corticoreticular cerebellar pathway{from cerebral cortex to reticular information in brain steam then to cerebellum ◄ cortico-olivary cerebellar pathway[from cerebral cortex to olivary then to cerebellum} █ Summary for Cerebellar efferent fibers: 5 Globose-emboliform-rubral pathway☻ Dentothalamic pathway ☻ Fastigial reticular pathway☻ Fastigial vestibular pathway ☻ █ summary for cerebllar afferent fibers: ☻ Afferent fibers from cerebral cortex: corticopontocerebellar pathway ☻Afferent fibers from spinal cord: Anterior and posterior spinocerebellar tracts ☻Afferent fibers from vestibular nerve █ Summary for the function of cerebllum :-Planning & coordinating the activities of muscle groups -Control posture -Balance & coordination -Regulation of muscle tone ☼☼ The cerebellum does not initiate movement, but it contributes to coordination, precision, and accurate timing 6 ☼☼damage to the cerebellum does not cause paralysis, but instead produces disorders in fine movement, equilibrium, posture, and motor learning. Signs & symptoms of cerebellar disease█ 1) Loss of the ability to coordinate muscular movement (Ataxia ) { the main cause is cerebellar injure} 2) the inability to judge on nose test(dysmetria) position of tip of nose and when to stop like finger he can not define the righ 3) the inability to perform rapid alternating movements spination & pronation (adiadochokinesia) 4) movement tremors (intention tremor) 5) staggering, wide based walking {for balance} 6) tendency toward falling 7 7) weak muscles (hypotonia) 8) slurred speech 9) abnormal eye movements (nystagmus) ☼☼Cerebellar injury results in movements that are slow and uncoordinated. Individuals with cerebellar lesions tend to sway and stagger when walking ☼☼A lesion in one cerebellar hemisphere gives rise to signs & symptoms that are limited to the same side of the body ☼☼A lesion in both cerebellar hemisphere gives rise to signs & symptoms that are the patient can not walk or standup{ tendency toward falling } 8 Lower +upper Basal ganglion neurons nurone Cerebellum The main effectors on the body movement Cerebellar ataxia : have the following if there is for ex Left cerebellar tumor -Sways to the right in standing poition - Steady on the right leg - Unsteady on the left leg -ataxic gait 9