Neuroscience is the study of the brain and nervous system in both health and disease. It is a multidisciplinary branch of biology that combines physiology, anatomy, molecular biology, developmental biology, cytology and psychology and is directed at understanding the fundamental properties of neurons and neural circuits. The central nervous system (CNS) and peripheral nervous system (PNS) work together to coordinate basic functions such as moving and breathing, as well as higher order functions such as thought, speech and emotion. In many species the nervous system is the most complex organ system in the body, with most complexity residing in the brain. The human brain contains around one hundred billion neurons - cells specialized for communication with other neurons and other cell types – with one hundred trillion synapses connecting them to each other in vast and complex networks.
Neurological diseases can be classified according to their etiology. They can be caused by genetic mutations, development abnormalities, degeneration, trauma, malignancy and infection. Pharmacological interventions for many neurological diseases, especially the degenerative conditions, are limited to alleviation of symptoms. The understanding of the nervous system is a major challenge for biological science and prevention and better treatment of neurological disorders a key goal of medical research.