Due to its very complicated structure, the nervous system is involved in almost every function in the body. Examples of the enormous number of functions of the nervous system include the processing and storing of memory which is done in a special structure of the limbic system that is called the hippocampus. In addition, all of our senses are mediated by special nerves that are called cranial nerves. These nerves originate each in a different part of the brain according to the sense that is involved.
These cranial nerves transmit sensory data to different parts of the cerebral cortex where they are processed and interpreted appropriately. Another important function in the body which involves the nervous system is the muscles reflexes in the spinal cord. These reflexes are mediated by motor neurons in the various levels of the spinal cord. The manner of walking or gait is also mediated by the action of the nervous system. Injury to the nervous system at the level of the cerebral cortex or the spinal cord can lead to walking problems or even paralysis in the affected area of the body. Also psychological concepts such as thinking and perception are also processed in the brain in which they are part of the brain.
The nervous system is divided into subdivisions due to its intricate structure. It is divided into central nervous system and a peripheral nervous system. The central nervous system is comprised of the brain and the spinal cord while the peripheral nervous system is comprised of the peripheral nerves, in addition to the cranial nerves which are considered part of the peripheral nervous system although they originate in the brain.
Also the ganglia and the free nerve endings are considered as part of the peripheral nervous system. Functionally speaking, the nervous system is divided into somatic nervous system and autonomic nervous system. The somatic nervous system provides sensory and motor innervation to all parts of the body including the skeletal muscles. This is except for internal organs in the body such as smooth muscles and glands which are supplied with autonomic innervation.
The autonomic nervous system consists of autonomic innervation to organs in the body such as the gastrointestinal system and the abdominal organs such as the liver and the pancreas. The autonomic nervous system is as the name implies autonomic and is not under voluntary action of the body such as occurs with skeletal muscles. The autonomic nervous system is divided into three substructures. These are: The sympathetic nervous system and the parasympathetic nervous system in addition to the enteric nervous system.
The sympathetic nervous system usually has its origin in the upper part of the spinal cord while the parasympathetic nervous system has its origin in nuclei in the brainstem in addition to the sacral part of the spinal cord. The enteric nervous system is a special form of nervous system that is located within the walls of the intestine. This nervous system responds to sympathetic as well as to parasympathetic innervation by making synapses with neurons of both of these divisions of the autonomic nervous system.
The sympathetic nervous system is usually working in a state of tension and anxiety. The parasympathetic nervous system is especially important for the function of the gastrointestinal tract in which neurons of the vagus nerve synapse with neurons of the enteric nervous system in the intestine which then stimulate the peristaltic motion of the intestinal muscles. The sacral part of the spinal cord usually supplies parasympathetic innervation to the urogenital organs, including the rectum and the anal canal of the colon.
The most important disorders of the nervous system which involve the brain are the movement disorders caused by damage to the brain in certain area such as the motor cortex and the basal ganglia. This is in addition to disorders of the cerebellum. An example of such a disorder is seen in the paralysis of the legs in which case it can occur due to either a damage in the motor cortex or due to a damage in the spinal cord in its lumbar region.
Also ataxia or muscle uncoordination can occur in disorders which involve the cerebellum of the brain. In addition, motor disorders can be seen in a neurological disorder which is called amyotrophic lateral sclerosis in which the amino acid glutamate accumulates in the brain causing excitotoxicity that can cause damage to the motor neurons. Also in other diseases which do not have neurological origin such as diabetes mellitus and syphilis there is seen neurological symptoms such as hyporeflexia due to damage in the neurons of the spinal cord.
