Amygdala - Located in the middle of the brain, this almond shaped complex of related nuclei is a critical processor area for the senses. Connected to the hippocampus, it plays a role in emotionally laden memories. It contains a huge number of opiate receptor sites implicated in rage, fear and sexual feelings. It is part of the limbic system.

Axons - These are the long fibers extending from the brain cells (neurons) that carry the output (an electrical nerve impulse) to other neurons. They can be up to a meter long. There is just one axon per neuron, but axons can subdivide to connect with many dendrites.

Basal ganglia - Clusters of nuclei deep within the cerebrum, and the upper parts of the brain stem that play an important part in producing smooth, continuous muscular actions in starting and stopping movements.

Brain stem - Located at the top of the spinal cord, it links the lower brain with the middle of the brain and cerebral hemispheres.

Broca’s area - This is part of the left frontal lobe in the cerebrum. It converts thoughts into sounds (or written words) and sends the message to the motor area. Impulses go first to Wernicke’s area, then to Broca’s area.

Cerebellum - A cauliflower-shaped structure located below the occipital area and next to the brain stem. The word is Latin for "little brain." Traditionally, research linked it to balance, posture, coordination and muscle movements. Newer research has linked it to cognition, novelty and emotions.

Cerebral Cortex - This is the newspaper-sized, 1/4 inch thick, outermost layer of the cerebrum. It is wrinkled, six layers deep, and packed with neurons. Cortex is the Latin word for "bark" or "rind."

Cerebrum - This is the largest part of the brain, composed of the left and right hemisphere. It has frontal, parietal, temporal and occipital lobes.

Corpus callosum - A white-matter bundle of 200-300 million nerve fibers that connect the left and right hemispheres.

Dendrites - These are the strand-like fibers emanating from the neuron. Similar to spider webs or cracks in a wall, they are receptor sites for axons. Each cell usually has many, many dendrites.

Dopamine - A powerful and common neurotransmitter, primarily involved in producing positive moods or feelings. It plays a role in movements, also.

Endorphin - A natural opiate, this neurotransmitter is similar to morphine. It is produced in the pituitary gland. It protects against excessive pain, and is released with ACTH into the brain.

Frontal lobes - One of four main areas of the cerebrum, the upper brain area. It controls voluntary movement, verbal expression, problem solving, willpower and planning.

Hippocampus - Found deep in the temporal lobe, it is crescent-shaped, and strongly involved in learning and memory formation. It is part of the limbic system.

Hypothalamus - Located in the bottom center of the middle brain under the thalamus. Complex thermostat-like structure that influences and regulates appetite, hormone secretion, digestion, sexuality, circulation, emotions and sleep. Part of the limbic system.

Lateralization - Refers to the activity of using one hemisphere more than another. The term "relative lateralization" is more accurate because we are usually using at least some of the left and right hemisphere at the same time.

Limbic system - An older term coined by Paul MacLean in 1952. It describes a group of connected structures in the mid-brain area, which includes the hypothalamus, amygdala, thalamus and  hippocampus.

Neuron - One of two types of brain cells. We have about 100 billion of these. They receive stimulation from their branches, called dendrites. They communicate to other neurons by firing a nerve impulse along an axon.

Neurotransmitters - Our brain’s biochemical messengers. We have more than 50. They act as stimuli or inhibitors to activate or suppress the electrical impulse traveling from the cell body through the axon.

Occipital lobe - Located in the rear of the cerebrum, this lobe processes our vision.

Oxytocin - A peptide also known as the "commitment molcule." It is released during sex and pregnancy and influences "unlearning" and pair bonding.

Parietal lobe - One of the four major areas of the cerebrum. This area deals with reception of sensory information from the body’s opposite side. It also plays a part in reading, writing, language and calculation.

Peptide - A class of hormones made of chains of amino acids. These proteins also serve as information messengers for states, moods and thinking. They travel throughout the body.

Serotonin - A common neurotransmitter, most responsible for inducing relaxation, regulating mood and sleep. Antidepressants (like Prozac) suppress the absorption of serotonin.

Temporal lobes - Located on the side of the cerebrum, it is an area believed to be responsible for the senses, listening, language, learning and memory storage.

Thalamus - Located deep within the middle of the brain, it is a key sensory relay station.

Vasopressin - A stress-related hormone that is partly responsible for aggression.

Wernicke’s area - Refers to the upper back of the temporal lobe. Here the brain converts thoughts into language.