CEREBELLUM Functions Maintenance of balance and posture Coordination

CEREBELLUM Functions: Maintenance of balance and posture Coordination of voluntary movements Motor learning Cognitive functions

CEREBELLUM Anatomical division

CEREBELLUM Developmental division q archicerebellum § vestibulocerebellum q paleoocerebellum § spinocerebellum q neocerebellum § cerebro- (ponto-) cerebellum

CEREBELLUM Functional division q VC § flocculonodular lobe § vestibular ncll. q SC - median zone § vermis § ncl. fastigii q SC - paramedian zone § intermediate cortex § ncll. emboliformis et globosus q CC - lateral zone § cortex cerebellar hemispheres § ncl. dentatus

Rubro – olivary tract

CEREBELLAR CORTEX

Connections of the vestibulocerebellum Vestibular ncll. Vestibulospinal tracts Pontine ncll. Vestibulocerebellar tract Flocculonodular lobe (vestibulocerebellum) Spinal motor neurons LGB + Sup. Col. Vestibular apparatus Ø vestibular reflexes Ø postural maintanence

Connections of the spinocerebellum – median zone Ncl. thor. (S-C) Vestibulospinal tracts Spinocerebellar tracts Bulbocerebellar tract Cuneocerebellar tract FR GN + CN Vestibular ncll. Ncl. fast. Reticulosp. tracts Vermis (spinocerebellum) Spinal motor neurons Ant. corticoospinal tract MC Th. VL Ø control of medial descending (motor) system

Connections of the spinocerebellum – paramedian zone GN + CN Ncll. emb. + glob. Ncl. thor. (S-C) RN Rubrosp. tract Spinocerebellar tracts Bulbocerebellar tract Cuneocerebellar tract Intermediate zone (spinocerebellum) MC Lat. corticoospinal tract Th. VL Spinal motor neurons Ø control of lateral descending (motor) system

Connections of the cerebro(ponto)cerebellum – lateral zone Th. VL Pontocerebellar tract Pontine ncll. Ncl. dentatus Lateral zone (pontocerebellum) Lat. corticoospinal tract Corticopontine tract Motor cortex Ø planning and timing of movements Ø cognitive functions Spinal motor neurons

Somatotopic organization Projection of both spinocerebellar pathways and motor cortex q ipsilateral anterior lobe q bilateral paramedian (intermediate) zone

BASAL GANGLIA Striatum (neostriatum) – ncl. caudatus (D) - putamen (D) - ncl. accumbens (V) Pallidum (paleostriatum) – globus pallidus ext. s. Substantia nigra – pars reticularis - pars compacta Ncl. subthalamicus int. s.

Ncl caudatus + putamen = dorsal striatum Globus pallidus C = dorsal pallidum Substantia innominata: Pu GP VP VS VS = ventr. striatum Ncl. accumbens septi VP = ventral pallidum Ncl. basalis Meynerti

Basal ganglia afferents: q cortex q substantia nigra – pars compacta q intralaminar ncll. of thalamus (CM)

Basal ganglia efferents: q GPi q SN – pars reticularis Ø Th. VA/VL Ø Th. CM (ansa lenticularis + fasciculus lenticularis → fasciculus thalamicus)

Basal ganglia intrinsic connections: q q q Striatopallidal p. Striatonigral p. GPe → STN → GP, SNr. Nigrostriatal p.

Motor loop

SPINAL REFLEXES q type of afferents § somatic spinal reflexes § visceral spinal reflexes q type of somatosensor § proprioceptive reflexes § exteroceptive reflexes q number of involved spinal segments § monosegmental spinal reflexes § polysegmental spinal reflexes q number of synapses § monosynaptic reflexes § disynaptic reflexes § polysynaptic reflexes

Myotatic reflex Withdrawal reflex

Myotatic (stretch) reflex

Reflex loop of Golgi tendon organ (inverse myotatic reflex) Ib

Flexor (withdrawal) reflex

Renshaw cells

Gamma loop

EYE MOVEMENTS q Fovea centralis – area of most acute vision q Coordination of 12 oculomotor muscles q Eye movements § conjugated – both eyes in same direction § vergent - during motion of object to and from us Ø convergent Ø divergent

Four basic types of eye movements q Saccades q Smooth pursuit movements q Vergence movements q Vestibulo-ocular movements

Saccadic eye movements q horizontal gaze center - PPRF q vertical gaze center – RF of the midbrain Ø superior colliculi – information from FEF, retina, auditory, and tactile i.

Smooth pursuit movements q elicited by a moving visual target that the eyes follow voluntarily or under direction q the moving visual target is required to initiate this eye movement

Vestibulo-ocular movements q stabilize the eyes relative to the external world, thus compensating for head movements

Vergence movements

Illustrations were copied from: Neuroscience Online, the Open-Access Neuroscience Electronic Textbook Department of Neurobiology and Anatomy University of Texas Medical School at Houston