Glossary

action potential	An electric nerve impulse that travels through a neuron when it is set off by a "trigger," changing the neuron's charge from negative to positive



all-or-none law	The rule that neurons are either on or off



association areas	One of the major areas of the brain; the site of the higher mental processes such as thought, language, memory, and speech



autonomic division	The part of the nervous system that controls involuntary movement (the actions of the heart, glands, lungs, and other organs)autonomic_division (200.0K)



axon	The part of the neuron that carries messages destined for other neuronsaxon (102.0K)



behavioral genetics	The study of the effects of heredity on behavior



biofeedback	A procedure in which a person learns to control through conscious thought internal physiological processes such as blood pressure, heart and respiration rate, skin temperature, sweating, and constriction of particular muscles



central core	The "old brain," which controls such basic functions as eating and sleeping and is common to all vertebrates



central nervous system (CNS)	The system that includes the brain and spinal cord



cerebellum	The part of the brain that controls bodily balancecerebellum (93.0K)



cerebral cortex	The "new brain," responsible for the most sophisticated information processing in the brain; contains the lobescerebral_cortex (184.0K)



dendrites	A cluster of fibers at one end of a neuron that receive messages from other neurons



endocrine system	A chemical communication network that sends messages throughout the nervous system via the bloodstreamendocrine_system (139.0K)



evolutionary psychology	The branch of psychology that seeks to identify behavior patterns that result from our genetic inheritance from our ancestors



excitatory message	A chemical message that makes it more likely that a receiving neuron will fire and an action potential will travel down its axons



hemispheres	The two symmetrical left and right halves of the brain; each controls the side of the body opposite to it



hormones	Chemicals that circulate through the blood and affect the functioning or growth of other parts of the bodyhormones (141.0K)



hypothalamus	A tiny part of the brain, located below the thalamus of the brain, that maintains homeostasis and produces and regulates vital, basic behavior such as eating, drinking, and sexual behaviorhypothalamus (254.0K)



inhibitory message	A chemical message that prevents a receiving neuron from firing



interneurons	Neurons that connect sensory and motor neurons, carrying messages between the two



lateralization	The dominance of one hemisphere of the brain in specific functionslateralization (111.0K)



limbic system	The part of the brain located outside the "new brain" that controls eating, aggression, and reproduction



lobes	The four major sections of the cerebral cortex: frontal, parietal, temporal, and occipital



motor area	The part of the cortex that is largely responsible for the voluntary movement of particular parts of the body



motor (efferent) neurons	Neurons that communicate information from the nervous system to muscles and glands of the body



myelin sheath	Specialized cells of fat and protein that wrap themselves around the axon, providing a protective coatingmyelin_sheath (180.0K)



neurons	Nerve cells, the basic elements of the nervous systemneurons (95.0K)



neurotransmitters	Chemicals that carry messages across the synapse to the dendrite (and sometimes the cell body) of a receiver neuronneurotransmitters (176.0K)



parasympathetic division	The part of the autonomic division of the nervous system that acts to calm the body after the emergency situation is resolvedparasympathetic_division (186.0K)



peripheral nervous system	The part of the nervous system that includes the autonomic and somatic subdivisions; made up of long axons and dendrites, it branches out from the spinal cord and brain and reaches the extremities of the body.peripheral_nervous_system (285.0K)



pituitary gland	The "master gland," the major component of the endocrine system, which secretes hormones that control growth



reflexes	Unlearned, involuntary responses that occur automatically in the presence of certain stimuli



resting state	The state in which there is a negative electrical charge of about -70 millivolts within the neuron



reticular formation	The part of the brain from the medulla through the pons made up of groups of nerve cells that can immediately activate other parts of the brain to produce general bodily arousalreticular_formation (238.0K)



reuptake	The reabsorption of neurotransmitters by a terminal button



sensory area	The site in the brain of the tissue that corresponds to each of the senses, with the degree of sensitivity relating to the amount of tissue



sensory (afferent) neurons	Neurons that transmit information from the perimeter of the body to the central nervous system



somatic division	The part of the nervous system that specializes in the control of voluntary movements and the communication of information to and from the sense organs



spinal cord	A bundle of nerves that leaves the brain and runs down the length of the back and is the main means for transmitting messages between the brain and the body



split-brain patient	A person who suffers from independent functioning of the two halves of the brain, as a result of which the sides of the body work in disharmony



sympathetic division	The part of the autonomic division of the nervous system that acts to prepare the body in stressful emergency situations, engaging all the organism's resources to respond to a threat



synapse	The space between two neurons where the axon of a sending neuron communicates with the dendrites of a receiving neuron using chemical messages



terminal buttons	Small bulges at the end of axons that send messages to other neurons



thalamus	The part of the brain located in the middle of the central core that acts primarily as a busy relay station, mostly for information concerning the senses

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