In Depth: Nervous System
The nervous system consists of the brain, spinal cord, and nerves. This is the way the body communicates with the brain and vice versa.
The nervous system is divided into two key parts:
- Central nervous system (CNS): the primary control center for the body, composed of the brain and spinal cord.
- Peripheral nervous system (PNS): a network of nerves that connects the rest of the body to the CNS.
The two systems collaborate to collect information from inside and outside the body. The systems collect and process information and then dispatch instructions to the rest of the body.
The brain is the processing destination for information gathered by the rest of the nervous system. Once data arrives, the brain sorts and files it before sending out any necessary commands. These instructions cause the body to react, like when you instinctively pull your hand away from a hot stove.
Information conveyed through the nervous system moves along networks of cells called neurons. These neurons can only send information one way. Those transmitting to the brain are sensory neurons; those that transmit from the brain are known as motor neurons.
Although the brain is the control center, its job would not be possible without the spinal cord, which is the major conduit for information traveling between brain and body.
The brain is divided into many different sections, including the cerebrum and brain stem. These parts handle pieces of the brain’s overall workload, including storing and retrieving memory and making body movements smooth.
The CNS is composed of two types of tissue, called white matter and gray matter. Gray matter contains cell bodies, dendrites (branches of a nerve cell), and synapses (the gaps between cells). White matter is made of axons, the threadlike parts of nerve cells that transmit signals from one cell to the next. Nerve signals are created and processed in gray matter. White matter’s main function is to transmit these signals.
Peripheral system nerves branch from either the brain stem or the spinal cord. Each nerve is connected to a particular area of the torso or limbs and is responsible for communication to and from those regions.
The PNS can also be divided into smaller pieces: the somatic and autonomic systems. The somatic involves parts of the body a person can command at will, such as moving your arm, walking, and more. The autonomic helps run involuntary functions such as pumping blood, breathing, and digestion.
The nervous system can suffer from a number of afflictions, including cancer. Other problems include multiple sclerosis, in which damaged nerves prevent signals from traveling along them, or meningitis, which causes an inflammation of the membranes surrounding the brain and spinal cord.