This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Neuroanatomy, Head and Neck, Subject name: Anatomy
[{'content': 'All are true about Substantia nigra except:- \nSelect and explain. \nA. Pars compacta is rich in melanin, B. Pallor of substantia nigra indicates Parkinsonism, C. Afferents are derived from caudate nucleus, D. Efferent fibers are rich in GABA', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Substantia nigra is the pigmented sheet of nerve cells between the tegmentum and crus cerebri of mid brain It extends from the cranial border of Pons to sub thalamic region. It consists of dorsal pigmented and compact pa known as pars compacta (cell rich zone) and ventral less pigmented reticular pa known as pars reticularis (cell poor zone). Neurons of pars compacta are rich in melanin and those of pars reticularis are rich in iron. Afferents:- From the caudate nucleus and putamen as Strio-nigral fibers. These fibers convey Gama Amino Butyric Acid (GABA) to pars reticularis and exe inhibition in neuro transmission. Efferents:- They are Nigro-striate fibers from pars compacta to caudate nucleus and putamen. They are rich in dopamine which on reaching the neurons of striatum inhibits the excitation of later and prevent tremor and other involuntary acts.', 'role': 'assistant'}]