Short Refresher on Neurons

You are so repulsed by broccoli that you detect its bitter taste buried in a vegetable medley and spit it into your napkin. Backstage, your brain and nervous system carry out actions such as this one through a wave of communication between it's billions of nerve cells or neurons.

Each neuron that makes up the communication line, itself, resembles broccoli. Incoming messages are received in the dendrites, which mirror the branching buds of the veggie. The chemical messages pass down these sprouts into the cell body and then through one main long stalk or axon of the neuron. Finally the signal heads out to connected neurons.

Neurons vary in the amount of information they receive and transmit. Some have an extremely large social circle and receive and transmit thousands of messages. Others have only a few connections.

All messages, however, are passed to connected neurons in the form of chemicals called neurotransmitters. They flow from a message-sending neuron across a gap called a synapse and onto target neurons. The chemicals attach to a slot on the surface of the receiving neuron -- a protein called a receptor site. Many scientists compare the union to a key fitting in a lock. Once attached, different neurotransmitters either trigger "go" signals that allow the message to be passed to the next neuron in the communication line or produce "stop" signals that prevent the message from being forwarded. The signals are in the form of charged particles or ions. A large concentration of positively-charged particles entering a receiving neuron tells it to pass on the message. On the other hand, a large concentration of negatively-charged particles entering the neuron will inhibit it from passing on the message.

The brain keeps tight control of this message delivery system to avoid communication chaos. A single receiving neuron has thousands of receptor sites and may receive many different messages and passwords at once. Each neuron adds up the incoming signals and determines whether or not to pass the information along to other cells. Neuron communication is under intense investigation by researchers because when it goes out of balance ailments ranging from epilepsy to memory disorders can occur.