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Physical
Central Nervous System
The central nervous system is the brain and spinal cord, the part of the nervous system that gathers information and coordinates the whole body.
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The idea
The central nervous system (CNS) is the part of the nervous system made up mainly of the brain and the spinal cord. The retina, the light-sensing layer at the back of the eye, is technically part of it as well. It is called central because the brain gathers incoming information and coordinates the activity of every part of the body.
The brain is usually located in the head, near the organs for vision, hearing and smell. It receives information from the senses, processes it through thought and reasoning, and coordinates muscle activity and the release of hormones. In the human brain, each neuron is connected through synapses to several thousand other neurons, and the prefrontal cortex, which controls planning and self-control, is especially well developed.
The spinal cord is a long, thin tube of nervous tissue that runs from the lower brainstem down inside the backbone, which protects it. It carries nerve signals from the brain's motor areas out to the body and carries sensory signals back to the brain. It also coordinates many reflexes by itself, and its circuits control rhythmic movements such as walking. In adults it is around 45 centimeters long in men and around 43 centimeters long in women.
Check yourself
Question 1 of 2
Which part of the eye is technically part of the central nervous system?
Composition
what it's made of
- Brain — The organ in the head that processes sensory information and coordinates muscles and hormones.
- Spinal cord — The tube of nervous tissue inside the backbone that carries signals between the brain and the body.
- Retina — The light-sensing layer of the eye, technically part of the CNS.
- Neurons and synapses — Nerve cells and the junctions that connect each one to many others.
- Reflex arcs — Circuits in the spinal cord that can control reflexes without the brain.
Connection
how it relates
Under Nervous System
Change
how and why it evolves
- Past
- Central nervous systems evolved in many animal groups, but only arthropods, cephalopods and vertebrates developed a true brain. Simpler precursor structures exist in animals such as gastropods and lancelets. The first real progress toward a modern understanding of nerves came when Luigi Galvani found that a shock of static electricity applied to a dead frog's nerve could make its leg contract. Until the 1950s, it was generally believed that the brain essentially shuts off during sleep, but its activity actually continues in very different patterns.
- Now
- Scientists now understand how individual brain cells work in considerable detail, but how large groups of them cooperate is still unsolved.
- Next
- Models that treat the brain as a biological computer will likely keep guiding research, even though the brain works very differently from a digital computer.