Substantia nigra

Substantia nigra (after Samuel Thomas Soemmerring also Soemmerring ganglion ) refers to a portion of the brain. It is a core complex in the area of the midbrain ( mesencephalon ), which is characterized by a high intracellular content of iron and melanin dark (Latin niger / gra / grum, black ' ) colored.

Anatomy

The substantia nigra is located in the midbrain dorsal to the cerebral peduncle. A distinction is morphologically a dark pars compacta ( SNc ) with densely packed, melanin-containing neurons and a reddish pars reticulata ( SNr ), notice of which nerve cells by a particularly high iron content.

The substantia nigra nerve fibers extend feeding ( afferent ) from the motor cortex and the premotor cortex, which are known as Fibrae corticonigrales. Moreover, there is afferents from the caudate nucleus and the putamen, the Fibrae called strionigrales.

The lead-out nerve fibers ( efferent ) draw on the Fibrae nigrostriatal to the striatum ( caudate nucleus and putamen together = ) and the thalamus. Histochemically, various neurotransmitters detected in the neurons of the substantia nigra. In the pars compacta impress a particularly high dopamine content.

Physiology

The substantia nigra is divided into various circuits of the extrapyramidal system and is in this way with the cerebral cortex, striatum, subthalamic nucleus, thalamus and other brain structures associated. About their dopaminergic neurons are mediated signals, which are particularly strong in the planning and the beginning of a movement ( " starter function ").

Pathophysiology

A failure of the dopaminergic system leads to a loss of inhibition of other components of the circuit and thus the symptoms of Parkinson's disease. In contrast, a failure of the subthalamic nucleus or the external portions of the globe leads pallidus to a relative overactivity of the neurons of the substantia nigra and thus to diseases such as Huntington's disease ( pallidum ) or the Hemiballism ( subthalamic nucleus ).