Glossary

Axon: A long, branching outgrowth of a neuron that carries information, in the form of a nerve impulse, away from the cell body of the neuron. Neurons typically have just one axon, which can be over a foot long. A neuron delivers information to other cells through the axon terminals at the end of its axon.

Circadian Rhythm: A cycle of behavior or physiological change lasting approximately 24 hours.

Dendrite: A branching outgrowth of a neuron that carries information, in the form of a nerve impulse, into the cell body of the neuron. Each nerve usually has many dendrites.

Glutamate: An amino acid neurotransmitter that acts to excite neurons. Glutamate stimulates N-methyl-d-aspartate (NMDA) and alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA). AMPA receptors have been implicated in activities ranging from learning and memory to development and specification of nerve contacts in developing animals. Stimulation of NMDA receptors may promote beneficial changes, whereas overstimulation may be a cause of nerve cell damage or death in neurological trauma and stroke.

Inhibition: A synaptic message that prevents a receiving neuron from firing.

Long-term potentiation (LTP): The molecular system by which the brain transforms short-term memories into long-term memories, resulting in structural and functional changes in neural networks.

Neuron: A nerve cell specialized for the transmission of information and characterized by long, fibrous projections called axons and shorter, branchlike projections called dendrites.

Neuroplasticity: A general term used to describe the adaptive changes in the structure and/or function of nerve cells or groups of nerve cells as a consequence of alterations in patterns of their use and disuse. Neuroplasticity occurs throughout life as well as in response to injuries to the nervous system.

Neurotransmitter: Brain chemicals released by nerve cells at synapses that influence the activity of other cells. Neurotransmitters may excite, inhibit, or otherwise influence the activity of cells.

Post-synaptic neuron: The neuron at the receiving end of a synaptic connection.

Potentiate: To increase the effect of or act synergistically with. See long-term potentiation.

Pre-synaptic neuron: The neuron at a synapse that is sending a neural signal.

Receptor: A molecule on the surface of a cell that recognizes specific chemicals, including neurotransmitters and hormones, and transmits the message into the cell on which the receptor resides.

Synapse: A physical gap between two neurons that functions as the site of information transfer from one neuron to another.

Synaptic cleft: The tiny gap between the sending and receiving neurons at a synapse, across which chemical neurotransmitters diffuse to pass along a neural signal.