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| Neuroscience | The study of the nervous system, especially the brain |
| Neuron | Highly specialized cell that communicates information in electrical and chemical form; a nerve cell |
| Glial Cell | Support cells that assist neurons by providing structural support, nutrition, and removal of cell wastes; manufacture myelin |
| Afferent Neuron | Sensory Neuron, conveys information to the brain from specialized receptor cells in sense organs and internal organs |
| Efferent Neuron | Motor Neuron, Type of neuron that signals muscles to relax or contract |
| Interneuron | Type of neuron that communicates information from one neuron to the next |
| Soma | Cell Body, The part of a neuron that contains the nucleus |
| Dendrites | Multiple short fibers that extend from the neuron's cell body and receive information from other neurons or from sensory receptor cells |
| Axon | The long, fluid-filled tube that carries a neuron's messages to other body areas |
| Myelin Sheath | A white, fatty covering wrapped around the axons of some neurons that increases their communication speed |
| Action Potential | A brief electrical impulse by which information is transmitted along the axon of a neuron |
| Stimulus Threshold | The minimum level of stimulation required to activate a particular neuron |
| Resting Potential | State in which a neuron is prepared to activate and communicate its message if it receives sufficient stimulation |
| All-or-None Law | The principle that either a neuron is sufficiently stimulated and an action potential occurs or a neuron is not sufficiently stimulated and an action potential does not occur |
| Synapse | The point of communication between two neurons |
| Synaptic Gap | The tiny space between the axon terminal of one neuron and the dendrite of an adjoining neuron |
| Axon Terminals | Branches at the end of the axon that contain tiny pouches, or sacs, called synaptic vesicles |
| Neurotransmitters | Chemical messengers manufactured by a neuron |
| Reuptake | The process by which neurotransmitter molecules detach from a postsynaptic neuron and are reabsorbed by a presynaptic neuron so they can be recycled and used again |
| Acetylcholine | Neurotransmitter that causes muscle contraction and is involved in memory function |
| Dopamine | Neurotransmitter involved in the regulation of bodily movement, thought processes, and rewarding sensations |
| Serotonin | Neurotransmitter involved in sleep and emotions |
| Norepinephrine | Neurotransmitter involved in learning and memory; also a hormone manufactured by adrenal glands |
| GABA | Gamma-Aminobutyric Acid, Neurotransmitter that usually communicates an inhibitory message |
| Endorphins | Neurotransmitters that regulate pain perceptions |
| Nervous System | The primary internal communication network of the body; divided into the central nervous system and the peripheral nervous system |
| Central Nervous System | Division of the nervous system that consists of the brain and spinal cord |
| Spinal Reflexes | Simple, automatic behaviors that are processed in the spinal cord |
| Peripheral Nervous System | Division of the nervous system that includes all the nerves lying outside the central nervous system |
| Somatic Nervous System | Subdivision of the peripheral nervous system that communicates sensory information to the central nervous system and carries motor messages from the central nervous system to the muscles |
| Autonomic Nervous System | Subdivision of the peripheral nervous system that regulates involuntary functions |
| Sympathetic Nervous System | Branch of the autonomic nervous system that produces rapid physical arousal in response to perceived emergencies or threats |
| Parasympathetic Nervous System | Branch of the autonomic nervous system that maintains normal bodily functions and conserves the body's physical resources |
| Endocrine System | System of glands located throughout the body that secrete hormones into the bloodstream |
| Hormones | Chemical messengers secreted into the bloodstream by endocrine glands |
| Pineal Gland | Produces melatonin, which helps regulates sleep-wake cycles |
| Thyroid Gland | Controls body metabolism rate |
| Pancreas | Regulates blood sugar and insulin levels; involved in hunger |
| Ovaries | Secrete estrogen and progesterone, which regulate female sexual development and reproduction and influence sexual behavior |
| Testes | Secrete testosterone, which regulates male sexual development and reproduction and influences sexual behavior |
| Pituitary Gland | Endocrine gland attached to the base of the brain that secretes hormones that affect the function of other glands as well as hormones that act directly on physical processes |
| Adrenal Glands | Pair of endocrine glands that are involved in the human stress response |
| Gonads | The endocrine glands that secrete hormones that regulate sexual characteristics and reproductive processes; ovaries in females and testes in males |
| Phrenology | A discredited pseudoscientific theory of the brain that claimed that personality characteristics, moral character, and intelligence could be determined by examining the bumps on a person's skull |
| Neurogenesis | The development of new neurons |
