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The pars compacta (SNpc) is one of two subdivisions of the substantia nigra of the midbrain (the other being the pars reticulata); it is situated medial to the pars reticulata. It is formed by dopaminergic neurons. [1] It projects to the striatum and portions of the cerebral cortex. [2] It is functionally involved in fine motor control.
Parkinson's disease is characterized by the loss of dopaminergic neurons in the substantia nigra pars compacta. [2] Although the substantia nigra appears as a continuous band in brain sections, anatomical studies have found that it actually consists of two parts with very different connections and functions: the pars compacta (SNpc) and the ...
The substantia nigra is located in the ventral midbrain of each hemisphere. It has two distinct parts, the pars compacta (SNc) and the pars reticulata (SNr). The pars compacta contains dopaminergic neurons from the A9 cell group that forms the nigrostriatal pathway that, by supplying dopamine to the striatum, relays information to the basal ganglia.
The dopaminergic pathways that project from the substantia nigra pars compacta (SNc) and ventral tegmental area (VTA) into the striatum (i.e., the nigrostriatal and mesolimbic pathways, respectively) form one component of a sequence of pathways known as the cortico-basal ganglia-thalamo-cortical loop.
Substantia nigra. Pars compacta; Pars reticulata; Interpeduncular nucleus; Cerebral peduncle. Crus cerebri; Mesencephalic cranial nerve nuclei. Oculomotor nucleus (III) Edinger-Westphal nucleus; Trochlear nucleus (IV) Mesencephalic duct (cerebral aqueduct, aqueduct of Sylvius)
Location of the substantia nigra within the basal ganglia. The substantia nigra is a midbrain gray matter portion of the basal ganglia that has two parts – the pars compacta (SNc) and the pars reticulata (SNr). SNr often works in unison with GPi, and the SNr–GPi complex inhibits the thalamus.
Indirect and direct pathways.Some neuroanatomy is excluded for simplicity.. The two major input structures of the circuit are the striatum and the subthalamic nucleus (STN). The striatum receives inputs from both the cortex and the pars compacta of the substantia nigra (SNc), while the STN only receives cortical inputs.
The pars compacta is the most lateral part of the substantia nigra and sends axons to the superior colliculus. [20] [28] The neurons have high firing rates which make them a fast-spiking pacemaker and they are involved in ocular saccades.