Neurons - The Basic Units of the Brain

A neuron is a cell that specializes in transmitting information to other cells in the nervous system. They are one of the most basic units of the brain, and a major player in your ability to think.

A typical neuron has a cell body (soma), dendrites, and a long, tail-like extension that conducts signals away from the neuron called an axon. An axon is covered with a substance called myelin sheath to help transmit information faster and more efficiently.

The axon carries information along an electrical path between the soma and the dendrites of neighboring neurons. It sends signals across a gap between the two cells known as a synaptic cleft and into the next neuron by releasing chemicals, called neurotransmitters.

When a signal exceeds a threshold, the neuron generates an electric charge (an action potential) in its axon. This energizes the dendrites, triggering the release of neurotransmitters from axon terminals to cross the synaptic cleft and reach the receptor sites on the dendrites of neighboring neurons. The neurotransmitters then enter the synapse and can trigger signals in neighboring cells to fire, or cause them not to fire.

Different types of neurons have different structures and are adapted for a variety of functions. A specific class of neurons, such as sensory neurons, have specialized dendrites and axons to receive and process information.

Another type of neuron, known as a motor neuron, sends signals to muscles and glands in the body. In some cases, a motor neuron may have no dendrites or an axon.

These neurons are responsible for sending commands to the muscles that move your hands and feet, or glands that secrete hormones. They also control your breathing and heart rate, and help you sense pain.

Neurons are also the basic units of learning, as they help animals remember and learn new things. For example, researchers first noticed that bird brains added neurons at a time when they were learning to sing a song. The scientists who discovered the new neurons thought that these newborn neurons might help birds learn to store and recognize patterns of a song.

The three main classes of neurons are sensory, motor, and interneurons. Sensory neurons receive incoming information and integrate it into a complete picture of what is happening. They can then relay this information to the central nervous system, or CNS.

Interneurons are the most common type of neuron, and they take information from other neurons and then relay it to other cells, muscles, or glands in your body. For example, if you picked up a hot coal, an interneuron would tell the CNS that the item was hot, and then a motor neuron that innervated the muscles of your fingers would tell them to let go.

Scientists are still trying to understand how neurons are formed and how they develop. They know that they start in areas of the body that are rich in super-powered cells, and that neurons live for a long time.