Snell's Clinical Neuroanatomy

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CHAPTER 7 Cerebellum and Its Connections

Superior cerebellar peduncle

Cerebral peduncle

Middle cerebellar peduncle

Vermis

Optic nerve

Oculomotor nerve

Trochlear nerve

Pons

Trigeminal nerve Vestibulocochlear nerve Abducens nerve

Olive Pyramid

Spinal root of accessory nerve

Inferior cerebellar peduncle

Medulla oblongata

Figure 7-9 Three cerebellar peduncles connecting the cerebellum to the rest of the central nervous system.

inhibitory information from the Purkinje cells. Efferent information from the deep cerebellar nuclei leaves the cerebellum to be distributed to the remainder of the brain and spinal cord. Cerebellar Cortical Neurotransmitters Pharmacologic research has suggested that the excit atory climbing and mossy afferent fibers use glutamate ( γ -aminobutyric acid) as the excitatory transmitter on the dendrites of the Purkinje cells. Further research has indicated that other afferent fibers entering the cortex liberate norepinephrine and serotonin at their endings that possibly modify the action of the glutamate on the Purkinje cells. Cerebellar Peduncles The cerebellum is linked to other parts of the central nervous system by numerous efferent and afferent fibers grouped together on each side into three large bundles, or peduncles (Fig. 7-9). Superior cerebellar peduncles connect the cerebellum to the midbrain, middle cerebel lar peduncles connect the cerebellum to the pons, and inferior cerebellar peduncles connect the cerebellum to the medulla oblongata. CEREBELLAR AFFERENT FIBERS The cerebellum receives major afferent tracts from the cerebral cortex, pons, medulla oblongata, and spi nal cord.

Cerebellar Afferent Fibers from the Cerebral Cortex

The cerebral cortex sends information to the cerebel lum by three pathways: (1) corticopontocerebellar, (2) cerebro-olivocerebellar, and (3) cerebroreticulocer ebellar pathways. Corticopontocerebellar Pathway The corticopontine fibers arise from nerve cells in the frontal, parietal, temporal, and occipital lobes of the cerebral cortex, descend through the corona radiata and internal capsule, and terminate on the pontine nuclei (Fig. 7-10). The pontine nuclei give rise to the transverse fibers of the pons , which cross the midline and enter the opposite cerebellar hemisphere as the middle cerebellar peduncle (see Figs. 5-16 and 5-17). Cerebro-Olivocerebellar Pathway The cortico-olivary fibers arise from nerve cells in the frontal, parietal, temporal, and occipital lobes of the cerebral cortex and descend through the corona radiata and internal capsule to terminate bilaterally on the infe rior olivary nuclei. The inferior olivary nuclei give rise to fibers that cross the midline and enter the opposite cerebellar hemisphere through the inferior cerebellar peduncle. These fibers terminate as the climbing fibers in the cerebellar cortex. Cerebroreticulocerebellar Pathway The corticoreticular fibers arise from nerve cells from many areas of the cerebral cortex, particularly the

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