| autonomic nervous system (ANS) | The part of the nervous system that governs the smooth muscles, the heart muscle, the glands, and the viscera and controls their functions, including physiological responses to emotion. It has two divisions, the sympathetic and parasympathetic.
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| behavior genetics | A subfield of psychology concerned with determining the extent to which behavior, including abnormal behavior, is influenced by genetics.
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| central nervous system (CNS) | The part of the nervous system made up of the brain and spinal cord.
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| cerebral cortex | Outermost part of the brain.
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| chromosomes | Threadlike structures in all the cells of the body that carry genes in a linear order.
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| computerized tomography (CT) | A technique for mapping brain structure in which X rays are passed through cross sections of the brain, measuring the density of the tissue in each section.
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| concordant | Refers to sharing the same disorder.
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| corpus callosum | A band of nerve fibers connecting the two hemispheres of the brain.
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| diathesis | A genetic predisposition toward an abnormal or diseased condition.
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| diathesis-stress model | The belief that certain genes or gene combinations may lead to a diathesis, or predisposition, toward a disorder and that, if this is combined with certain kinds of environmental stress, abnormal behavior will result. In schizophrenia research, this approach holds that a predisposition to schizophrenia is inherited but that the disorder must be triggered by environmental stresses.
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| dizygotic (DZ) twins | Twins who develop from two eggs fertilized by two different sperm; they have 50 percent of their genes in common.
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| down-regulation | Process where postsynaptic receptors decrease in number or become less sensitive to the neurotransmitter in response to too much neurotransmitter being released into the synapse.
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| endocrine system | The system of endocrine, or ductless, glands—such as the hypothalamus and the pituitary—that is closely integrated with the central nervous system and is responsible for the production of hormones.
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| event-related potentials | An EEG that measures changes in brain activity as a consequence of specific sensory, cognitive, or motor stimuli.
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| frontal lobe | Largest and anterior division of each cerebral hemisphere. Involved in motor function, language, memory, impulse control, and many other functions.
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| functional MRI (fMRI) | Variation of MRI that measures the magnetic action of blood oxygen and thus produces images of brain metabolism.
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| genes | The units of heredity on a chromosome that carry the instructions, inherited from the parents at conception, about the proteins that the body should produce. The proteins, in turn, determine the hereditary characteristics of the person—height, hair and eye color, and so on.
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| genetic marker | A gene with a known location on the human chromosome set; provides a clue to the location of a gene controlling a disorder.
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| genotype | The unique combination of genes that represents one's biological inheritance from one's parents.
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| genotype-environment correlation | The tendency for individuals' genetic predispositions for a trait or disorder to be associated with environmental experiences that also influence the trait or disorder.
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| hormones | Chemical messengers that are released directly into the bloodstream by the endocrine gland and that affect sexual functioning, physical growth and development, and emotional responses.
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| knockouts | Genes that are deleted to learn what they do—through observation of what the deletion does to behavior.
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| lateralization | The differences in structure and function between the right and the left hemispheres of the brain.
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| magnetic resonance imaging (MRI) | The use of magnetic fields to produce a highly precise picture of the brain.
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| mind-body problem | The issue of the relationship between the psychic and somatic aspects of human functioning.
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| monozygotic (MZ) twins | Twins who develop from the same fertilized egg and have exactly the same genotype.
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| nervous system | The vast electrochemical conducting network that extends from the brain through the rest of the body and carries information, in the form of electrical impulses, from the brain to the rest of the body and back to the brain.
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| neurons | The cells of the nervous system, which connect motor and receptor cells and transmit information throughout the body.
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| neuroscience perspective | A theory of abnormal behavior that concentrates on the physical aspects of a disorder in an effort to understand its characteristics.
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| neurotransmitter | One of a group of chemicals that facilitate the transmission of electrical impulses between nerve endings in the brain.
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| occipital lobe | Posterior lobe of each cerebral hemisphere; contains the visual center.
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| parasympathetic division | The division of the autonomic nervous system that decreases physical arousal and is usually dominant under less emotional conditions. It regulates breathing, heart rate, blood pressure, stomach and intestinal activity, and elimination. Cf.sympathetic division.
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| parietal lobe | Middle division of each cerebral hemisphere; involved in sensation, perception, and integrating sensory input.
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| peripheral nervous system | The network of nerve fibers that leads from the central nervous system to all parts of the body and carries out the commands of the CNS. It has two branches: the somatic nervous system and the autonomic nervous system.
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| phenotype | The unique combination of observable characteristics that results from the combination of a person's genotype with the environment.
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| polygenic | Refers to traits that are the products of the interaction of many genes.
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| positron emission tomography (PET) | A means of examining the brain. The patient is injected with a radioactively labeled sugar solution, and the path of the radioactive particles through the brain is traced.
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| postsynaptic receptors | Special proteins on the surface of neurons that bind with neurotransmitters squirted into the synapse from the dendrites of adjoining neurons. Molecules in the neurotransmitter fit into the receptor like a key into a lock.
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| psychopharmacology | Study of the drug treatment of psychological disorders.
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| psychosurgery | Surgery aimed at reducing abnormal behavior in the absence of any signs of organic brain pathology.
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| single photon emission computer tomography | Technique of brain imaging used to measure blood flow and glucose metabolism in the brain.
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| somatic nervous system | The part of the peripheral nervous system that senses and acts on the external world, relaying to the brain information picked up by the sense organs and transmitting the brain's messages to the skeletal muscles, which move the body.
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| sympathetic division | The division of the autonomic nervous system which becomes dominant in times of stress and which heightens the body's arousal, causing blood pressure, heart rate, perspiration, and adrenaline to increase, pupils to dilate, and salivation and digestive functions to diminish. Cf.parasympathetic division.
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| synapse | The gap between two neurons across which nerve impulses pass.
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| temporal lobe | Large lobe of each cerebral hemisphere that is located in front of the occipital lobe and contains the sensory center associated with hearing. Also involved in organization of sensory input.
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| up-regulation | Process where postsynaptic receptors increase in number or become more sensitive when presynaptic neurons are not releasing enough neurotransmitter to carry the impulse.
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