Nguồn gốc, khóa học, và phân phối các dự ly tâm của các globus pallidus (minh họa trên), và các kết nối của liềm đen (bản vẽ thấp hơn) mà không được thể hiện trong mối quan hệ để pallidum hoặc trong hình 7-22 trang 215 . Lenticularis ANSA (dashed line) vòm xung quanh viên nội bộ | 21Ó Synopsis of Functional Components Tracts Pathways and Systems Pallidal Efferents and Nigral Connections 7-23 The origin course and distribution of efferent projections of the globus pallidus upper illustration and connections of the substantia nigra lower drawing that were not shown in relation to the pallidum or in Figure 7 22 on page 215. The ansa lenticularis dashed line arches around the internal capsule and passes caudally to join in the formation of the thalamic fasciculus. Pallidosubthalamic fibers originate primarily from the lateral pallidal segment but pallidothalamic projections via the ansa lenticularis and lenticular fasciculus arise mainly from its medial segment. The substantia nigra has extensive connections the clinically most important being the dopaminergic ni-grostriatal fibers. The globus pallidus influences motor activity by way of pallidothalamic-thalamocortical-corticospinal and corticonuclear corticobulbar pathways. Neurotransmitters Gamma-aminobutyric acid -containing cells in the globus pallidus give rise to pallidonigral projections which end primarily in the substantia nigra-pars reticulata. Although GABA is also found in some subthalamopallidal axons this latter projection contains many glutaminergic fibers. Dopamine-containing GABA -containing and glycine -containing cells are present in the substantia nigra. Of these dopamine is found in pars compacta neu rons which give rise to nigrostriatal nigroamygdaloid and several other projections GABA in pars reticulata cells which give rise to ni-grocollicular and nigrothalamic fibers and glycine in some local circuit nigral neurons. Glutamate is found in corticonigral fibers and serotonin is associated with raphenigral fibers these latter fibers originate primarily from the nucleus raphe dorsalis. The dopaminergic projections to the frontal cortex shown here as arising only from SNpc originates from this cell group as well as from the immediately adjacent ventral tegmental area. .
