Nervous system physiology is the study of the human nervous system. The nervous is composed of two main parts: the central nervous system (CNS) and peripheral nervous system (PNS). The CNS and PNS work together through a system of neurons that extend throughout the body. Nervous system physiology also concerns itself with the disorders of the nervous system that appear due to injury or disease. The combined efforts of nervous system physiologists have led to new treatments for these disorders.
In the Western world, nervous system physiology began in ancient Greece when Aristotle hypothesized that the nerves, a term the Greeks invented, stemmed from the heart. Six hundred years later, the Roman physician Galen made a more accurate conclusion by stating the that brain was the nerves' control center, as all nerves eventually led there. Over the next 1,400 years, many thinkers including Leonardo da Vinci made their contributions to nervous system physiology. Only in the 20th century was medical science able to first discover the inner workings of the nervous system.
As Galen suggested in the second century, the brain is the key to the body's nervous system. It and the spinal cord are part of the CNS. The spinal cord sends sensory information to the processing centers of the brain. The brain's response, usually an instruction for the body to move in some way, is sent to the appropriate muscles. As the CNS is essential to human life, the brain and spinal cord are protected by bone from injury; a protective membrane known as the meninges blocks out some viruses, bacteria and foreign substances.
The peripheral nervous system is all the nerves outside of the brain and spinal cord. One's sense of touch stems from them. Though these nerves are not protected by bone or meninges, they have the ability to partially regenerate and/or heal if damage should occur. In the PNS, sensory neurons relay information to the brain and spinal chord. Motor neurons transmit the brain's instructions to the muscles.
The peripheral nervous system is further split into the somatic and autonomic nervous systems. The somatic nervous system is the groups of neurons that provide muscular control. The autonomic nervous system is the group of neurons that perform the brain's unconscious functions: digestion, heart rate, perspiration, etc.
Besides the study of the function and structure of the nervous system, nervous system physiology also includes disorders of the nervous system. Meningitis, for example, inflames the meninges covering the brain and spinal cord. Spinal cord injuries can cause loss of sensation and paralysis. Researchers studying nervous system disorders and general nervous system physiology have led to more effective treatments for preventing paralysis after spinal trauma. For example, methylprednisolone, if given intravenously within eight hours of injury, has show some success in preventing spinal cord damage.