Neurophysiology is a branch of physiology and neuroscience concerned with the functions of the nervous system and their mechanisms. The term neurophysiology originates from the Greek word νεῦρον ("nerve") and physiology (which is, in turn, derived from the Greek φύσις, meaning "nature", and -λογία, meaning "knowledge"). Neurophysiology has applications in the prevention, diagnosis, and treatment of many neurological and psychiatric diseases. Neurophysiological techniques are also used by clinical neurophysiologists to diagnose and monitor patients with neurological diseases. The field involves all levels of nervous system function, from molecules and cells to systems and whole organisms. Areas of study include:
The electrochemical properties of neurons Function and regulation of proteins in neurons and glia Metabolic reactions relevant to neural function Cell signalling in the nervous system Neurotransmission and synaptic plasticity Neural circuitry at microscopic and macroscopic levels The impact of neural functions on cognition and behaviour Pathophysiology of neurological and psychiatric disorders Experimental neurophysiologists use many techniques to study neural function. Electrophysiological techniques like electroencephalography (EEG), single cell recording, and extracellular recording of local field potentials are especially common. Multi-electrode arrays on semiconductor chips can perform in vitro extracellular recording and in vitro intracellular recording at scale. Magnetoencephalography is sometimes used in place of EEG. Immunohistochemistry, cell staining, in situ hybridisation, calcium imaging, and transmission electron microscopy are used to study cellular activity in the nervous system. Genetic engineering techniques may be used to study the impact of specific genes on neural functions. Pharmacological methods are used investigate the function of specific receptors in neurons and glia. Optogenetics and chemogenetics allow specific activation of neurons to study their functions. Functional magnetic resonance imaging and positron emission tomography can be used to measure metabolic changes in the brain. Finally, behavioural analysis is used to understand interactions between physiology and behaviour. Contemporary neurophysiology experiments often use multiple techniques together to develop a more complete understanding of their research areas.
History
Antiquity
Neurophysiology has been a subject of study since as early as 4,000 B.C. In the early B.C. years, most studies were of different natural sedatives like alcohol and poppy plants. In 1700 B.C., the Edwin Smith surgical papyrus was written. This papyrus was crucial in understanding how the ancient Egyptians understood the nervous system. This papyrus looked at different case studies about injuries to different parts of the body, most notably the head. The knowledge presents a rational and scientific approach to medicine in ancient Egypt. Beginning around 460 B.C., Hippocrates began to study epilepsy, and theorized that it had its origins in the brain. Hippocrates also theorized that the brain was involved in sensation, and that it was where intelligence was derived from. Hippocrates, as well as most ancient Greeks, believed that relaxation and a stress free environment was crucial in helping treat neurological disorders, that "healthy Mediterranean diet and daily moderate physical activity can prevent disease". In 280 B.C., Erasistratus of Chios theorized that there were divisions in vestibular processing in the brain, as well as deducing from observation that sensation was located there. In 177 C.E. Galen theorized that human thought occurred in the brain, as opposed to the heart as Aristotle had theorized. The optic chiasm, which is crucial to the visual system, was discovered around 100 C.E. by Marinus.
Middle ages Abū Bakr al-Rāzī (864 or 865–925 or 935 C.E.), also known by his Latin name Rhazes, a Persian physician, philosopher, and alchemist, wrote a book for al-Mansur (Kitāb al-Manṣūrī) of 26 sections on body structures, including nerves, muscles, and organs such as the eyes and heart. It was translated into Latin by Gerard of Cremona around 1180. c. 1000, Al-Zahrawi, living in Iberia, began to write about different surgical treatments for neurological disorders. He described a surgical procedure for treating such a neurological disease as migraine (in particular, ligation of the temporal artery for migraine), in his thirty-volume medical encyclopedia, the Kitab al-Tasrif manuscript, completed in the year 1000. Al-Zahrawi was first to discover the root cause of paralysis. In Persia, Avicenna (Ibn-Sina) presented detailed knowledge about skull fractures and their surgical treatments. In 1216, the first anatomy textbook in Europe, which included a description of the brain, was written by Mondino de Luzzi. In 1402, St Mary of Bethlehem Hospital (later known as Bedlam in Britain) was the first hospital used exclusively for the mentally ill.
16th century In 1504, Leonardo da Vinci continued his study of the human body with a wax cast of the human ventricle system. In 1536, Nicolo Massa described the effects of different diseases, such as syphilis on the nervous system. He also noticed that the ventricular cavities were filled with cerebrospinal fluid. In 1542, the term physiology was used for the first time by a French physician named Jean Fernel, to explain bodily function in relation to the brain.
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