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Ebook King’s applied anatomy of the central nervous system of domestic mammals (2/E): Part 2

Part 2 book “King’s applied anatomy of the central nervous system of domestic mammals” has contents: Extrapyramidal feedback and upper motor neuron disorders, summary of the somatic motor systems, the cerebellum, autonomic components of the central nervous system, the cerebral cortex and thalamus, embryological and comparative neuroanatomy, clinical neurology, imaging techniques for study of the central nervous system general considerations, and other contents. | 14 Extrapyramidal Feedback and Upper Motor Neuron Disorders Feedback of the Extrapyramidal System 14.1 Neuronal Centres of the Feedback Circuits Three major centres are involved in extrapyramidal feedback, namely the olivary nucleus, the cerebellum and the thalamus. 14.1.1 Olivary Nucleus The olivary nucleus is an intermediate station on the pathway from the higher extrapyramidal command centres to the cerebellum (Figure 14.1). It corresponds to the pontine nuclei in the pyramidal feedback circuit (Figure 12.2). The site of the olivary nucleus in the medulla oblongata is shown schematically in Figure 8.3 (see also Figure 22.7). Figure 14.1 Diagram of the feedback circuits of the extrapyramidal system. The motor centres are numbered 1 to 9. The red and black projections are the feedback circuits: the red projections lead to the cerebellum, and the black lines return from the cerebellum. The globus pallidus is the focal point of, and in this diagram represents, the basal nuclei. The globus pallidus has a feedback circuit through the thalamus and cerebral cortex, which enables the basal nuclei to collaborate with the cerebral cortex. n. = nucleus; nn. = nuclei; m.r.c. = motor reticular centre; and r.f. = reticular formation. 14.1.2 Cerebellum Two components of the cerebellum, i.e. the cerebellar cortex and the cerebellar nuclei (such as the dentate nucleus), are involved in extrapyramidal feedback circuits. Note the similarity to the pyramidal feedback circuit (Figure 12.2). 14.1.3 Thalamus The thalamus is the intermediate station between the cerebellum and the cerebral cortex, in those feedback circuits which return to the forebrain. The ventral group of thalamic nuclei controls all thalamic feedback circuits. Strictly, it is the ventrolateral thalamic nucleus, as in the pyramidal feedback circuits (Figure 12.2) (see Section 18.17). 14.2 Feedback Circuits All of the nine motor ‘command centres’ of the extrapyramidal system together with the pyramidal system .