Cerebellum cerebellum may be absent. The inherited neurological disorders Machado–Joseph disease, ataxia telangiectasia, and Friedreich's ataxia cause progressive neurodegeneration linked to cerebellar loss. Congenital brain malformations outside the cerebellum can, in turn, cause herniation of cerebellar tissue, as seen in some forms of Arnold–Chiari malformation. Other conditions that are closely linked to cerebellar degeneration include the idiopathic progressive neurological disorders multiple system atrophy and Ramsay Hunt syndrome type I, and the autoimmune disorder paraneoplastic cerebellar degeneration, in which tumors elsewhere in the body elicit an autoimmune response that causes neuronal loss in the cerebellum. Cerebellar atrophy can result from an acute
Hypothalamus the median eminence include vasopressin, oxytocin, and neurotensin. In the hypothalamic-neurohypophyseal axis, neurohypophysial hormones are released from the posterior pituitary, which is actually a prolongation of the hypothalamus, into the circulation. It is also known that hypothalamic-pituitary-adrenal axis (HPA) hormones are related to certain skin diseases and skin homeostasis. There is evidence linking hyperactivity of HPA hormones to stress-related skin diseases and skin tumors. The hypothalamus coordinates many hormonal and behavioural circadian rhythms, complex patterns of neuroendocrine outputs, complex homeostatic mechanisms, and important behaviours. The hypothalamus must, therefore, respond to many different signals, some of which generated externally and some