Brain is divided into central nervous system and peripheral nervous system. All the network and organs related to the central nervous system are located inside the brain whereas the peripheral nervous system is located outside the brain and You do not have access to view this node. Substantia Nigra is a cluster of cells and is an integral part of brainstem. The research on these cells has increased rapidly, once its key role in the occurrence of Parkinson’s disease came to the fore. Even today, although there are lots of medications to check the symptoms of this disorder, no cure has been found by science.
Substantia Nigra is associated with various terms like putamen, caudate, nucleus accumbens, subhtalmic nucleus, basal ganglia and historically as amygdala or claustrum. This basal ganglia or subatantia nigra is a group or cluster of nuclei that are placed deep inside the white matter of the cerebral cortex. Many times though, it is confused as ganglion which is the cell groups located external to Central nervous system. The substantial nigra is pigmented cell group placed in the brainstem and is found to generate dopamine. The ventrolateral tier cells of the substantia nigra are more prominently damaged during the Parkinson’s disease.
The exact location of substantia nigra is in the midbrain and it is located dorsal to cerebral peduncles. The two nuclei of substantia nigra-caudate and putamen combine with cells that are projected towards them to form striatum. These are nigrostriatal type of cells and make use of the neurotransmitter Dopamine.
The substantia nigra is divided in two portions:
Both the SNpc and the SNpr receives message from caudate and putamen. But SNpc sends it back from where it has come while SNpr transmits it to external of susbstantia nigra and contributes in controlling the movements of head and eye. The normal movement is made possible by dopamine which is produced by SNpc and hence it is more prominent of the two. In Parkinson’s disease, the SNpc functioning deteriorates and it is treated by oral dopamine precursor medication.
The substantia nigra is thought to be the lesion site in Parkinson’s disease or paralysis agitans. The common symptoms of this disease are muscular rigidity, resting tremor, bradykinesia or akinesia, unsteady stride or walk and unstable posture. The laterality of the deficits in this disease whether it is on the left or right is not considered. The major pathological result in this disease is that the melanin cells placed in pars compacta belonging to substantia nigra starts degenerating rapidly. The other part of pars compacta is termed as pars reticulate. Melanin content in substantia nigra is the end product of dopamine synthesis. The dopamine component travel through axoplasmic flow and reach the nerve terminals of caudate and putamen nucleus created striatum. From here this component is sent as a transmitter. The absence of this transmitter results in the unsteady abnormality in Parkinson’s disease.