The midbrain also called mesencephalon is a portion of the central nervous system associated with vision, hearing, motor control, sleep/wake, arousal, and temperature regulation.
The midbrain is located between the two developmental regions of the brain know as the forebrain and hindbrain.Within the midbrain is the reticular formation,Which is part of the tegmentum,a region of the brainstem that influences motor functions.The midbrain also contains the cerebrellum,and a large pigmented nucleus called the substantia nigra.The substantia nigra consists of two parts,the pars reticulata and the pars compacta.Cell of the pars compacta contain the dark pigment melanin;which are structures of the basal ganglia and are involved in mediating movement and coordination.These two strutures,in addition to the globus pallidus,from the striatum.By inhibiting the action of neurons in the caudate nucleus and the putamen, the dopaminergic cell of the pars compacta influence the neuronal output of the neurotransmitter GABA (gamma-aminobutyric acid).The neurons in turn project to the cell of the pars reticulata,which,by projecting fibres to the thalamus,are part of the output system of the corpus striatum.