Medical brain notes 24

  Section through the medulla at the level of the pyramidal decussation          Some features to be seen at this level have been reviewed. The pyramids and their decussation, the nucleus gracilis, the nucleus cuneatus, the spinal nucleus of the trigeminal nerve, the central grey matter, the central canal, and the uppermost part of the ventral grey column have been identified (Fig. 6.4). Now note the following additional features (Fig. 11.1).          The ventral grey column is separated from the central grey matter by decussating pyramidal fibres. The neurons in it give origin to the uppermost rootlets of the first cervical nerve, and to some fibres in the spinal root of the accessory nerve. The area between the ventral grey column and the spinal nucleus of the trigeminal nerve is occupied by the lower part of the reticular formation.             T...

  The Pons       Transverse sections through the lower and upper parts of the pons are illustrated in Figs. 11.5 and 11.7. Some features common to both these levels have been already considered (Fig. 6.7). The subdivision of the pons into dorsal and ventral parts and its relationship to the superior, middle and inferior cerebellar peduncles has been noted.         We have seen that the  ventral part of the pons  contains:  (a)  the pontine nuclei,  (b)  vertically running corticospinal and corticopontine fibres, and  (c)  transversely running fibres arising in the pontine nuclei and projecting to the opposite half of the cerebellum through the middle cerebellar peduncle.         The  pontine nuclei  (or  nuclei pontis ) receive corticopontine fibres from the frontal, temporal, parietal and occipital lobes of the cerebrum. Their effere...

  The Midbrain          Some features of the internal structure of the midbrain have been considered (Fig. 6.9). The subdivision of the midbrain into the tectum, the tegmentum, the substantia nigra, and the crus cerebri (or basis pedunculi) has been noted. The superior and inferior colliculi, the red nucleus and the reticular formation have been identified. Transverse sections through the midbrain         A transverse section through the midbrain at the level of the inferior colliculus is shown in Fig. 11.8 and a section at the level of the superior colliculus in Fig. 11.9. We will first consider those features that are common to both these levels.         The  crus cerebri  (or  basis pedunculi ) consists of fibres descending from the cerebral cortex. Its medial one-sixth is occupied by corticopontine fibres descending from the frontal lobe; and the lateral ...