The two main parts
The nervous system is the body's control and communication network. It is divided into the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS is made of the brain and the spinal cord, which process information and make decisions. The PNS is the network of nerves that link the CNS to every part of the body, carrying messages in and out. Together these parts let you sense your surroundings and control your muscles.
Key idea
The nervous system carries messages as tiny electrical signals called impulses. Neurons pass these impulses quickly so the body can react in a fraction of a second.
Neurons, the building blocks
A neuron is a nerve cell built to carry impulses. It has a cell body, thin branches called dendrites that receive impulses, and a long fibre called an axon that sends impulses onward. Many axons are wrapped in a fatty myelin sheath that insulates the fibre and speeds up the impulse. Three types work together: sensory neurons carry impulses from receptors to the CNS, relay neurons connect neurons inside the CNS, and motor neurons carry impulses to effectors such as muscles. Where two neurons meet there is a tiny gap called a synapse.
Jobs of the brain regions
The cerebrum controls thinking, memory and voluntary movement. The cerebellum keeps the body balanced and coordinates muscles. The medulla oblongata controls automatic actions such as heartbeat and breathing.
Remember
- CNS = brain + spinal cord.
- Dendrite receives, axon sends.
- Myelin insulates and speeds the impulse.