How It Works
Your nervous system
A breakdown of the specialised cells in your body which connect you with the outside world
Like any organisation, your success depends upon communication between your individual members. In a sense you actually are this communication, since it is the magic that makes you a single, clever creature. Your built-in communications network, known as the nervous system, perceives the outside world, keeps all body parts working in harmony and forms the thoughts and memories that make you unique.
The nervous system comprises hundreds of billions of specialised cells called neurons. A typical neuron consists of a compact cell body, protruding filaments called dendrites and a long single fibre called an axon. The axon can transmit signals to other neurons and to muscle cells, while the dendrite can receive signals from other neurons and sensory cells. A neuron’s axon may extend across the brain or body and branch off hundreds of times.
When something excites a neuron, the cell body will send an electrical charge down the length of an axon, triggering axon terminals to release chemicals called neurotransmitters. These neurotransmitters can travel to receptors on dendrites of an adjoining neuron across a small gap called a synapse. Depending on the type of neurotransmitter and receptor, the signal will either excite the adjoining neuron to fire an electrical charge down its own axon, or the signal may inhibit the neuron from firing. The complex connections and signal patterns among the hundreds of billions of neurons in your brain form thoughts, memories and other mental activities.
Axons that extend out from your brain and spinal column into your body can release neurotransmitters to trigger muscle movement and organ activity. This is how your brain controls your body. Neurons also carry signals from the body back to the brain. You perceive sights, sounds, smells and taste when sensory cells in your eyes, mouth, nose and ears excite nearby neurons. The neurons send an electrical signal up to the brain, which then interprets them. Sensory neurons near your skin and other parts of the body fire an electric signal in response to pressure, which your brain perceives as the sense of touch.