Psychology Vocab

Acetylcholine (ACh): a neurotransmitter that controls muscle contractions

Action potential: the electrical impulse that provides the basis for the conduction of a neural impulse along an axon of a neuron

Afferent neurons: neurons that transmit messages from sensory receptors to the spinal cord and brain; also called sensory neurons

All-or-none principle: the fact that a neuron fires an impulse of the same strength whenever its action potential is triggered

Amygdala: a part of the limbic system that apparently facilitates stereotypical aggressive responses

Aphasia: a disruption in the ability to understand or produce language

Autonomic nervous system (ANS): the division of the peripheral nervous system that regulates glands and activities such as heartbeat, respiration, digestion, and dilation of the pupils

Axon: a long, thin part of a neuron that transmits impulses to other neurons from bulb-shaped structures called axon terminals or terminal buttons

Broca’s aphasia: a language disorder characterized by slow, laborious speech

Central nervous system (CNS): the brain and spinal cord

Cerebellum: a part of the hindbrain involved in muscle coordination and balance

Cerebral cortex: the wrinkled surface area (gray matter) of the cerebrum

Cerebrum: the large mass of the forebrain, which consists of two hemispheres

Chromosome: a microscopic rod- shaped body in the cell nucleus carrying genes that transmit hereditary traits from generation to generation; humans normally have 46 chromosomes

Computerized axial tomography (CAT or CT): a method of brain imaging that passes a narrow X-ray beam through the head and measures the structures that reflect the beams from various angles, enabling a computer to generate a three-dimensional image

Corpus callosum: a thick fiber bundle that connects the hemispheres of the cortex

Dendrites: root-like structures, attached to the cell body of a neuron, that receive impulses, or incoming messages, from other neurons

Depolarize: to reduce the resting potential of a cell membrane from about 70 millivolts toward zero

Dizygotic (DZ) twins: twins that develop from two fertilized ova and who are thus as closely related as brothers and sisters in general; also called fraternal twins

DNA: acronym for deoxyribonucleic acid, the substance that forms the basic material of chromosomes; it takes the form of a double helix and contains the genetic code

Dopamine: a neurotransmitter that affects the ability to perceive pleasure, voluntary movement, and learning and memory; it is involved in Parkinson’s disease and appears to play a role in schizophrenia

Down syndrome: a condition caused by an extra chromosome on the 21st pair and characterized by mental deficiency, a broad face, and slanting eyes

Efferent neurons: neurons that transmit messages from the brain or spinal cord to muscles and glands; also called motor neurons

Electroencephalograph (EEG): a method of detecting brain waves by means of measuring the current between electrodes placed on the scalp

Endocrine system: the body’s system of ductless glands that secrete hormones and release them directly into the bloodstream

Endorphins: inhibitory neurotransmitters that occur naturally in the brain and in the bloodstream and are similar to the narcotic morphine in their functions and effects

Epilepsy: temporary disturbances of brain functions that involve sudden neural discharges

Evolutionary psychology: the branch of psychology that studies the ways in which adaptation and natural selection are connected with mental processes and behavior

Functional MRI (fMRI): a form of MRI that enables researchers to observe the brain in real time by taking repeated scans

Gamma-aminobutyric acid (GABA): an inhibitory neurotransmitter that apparently helps calm anxiety

Gene: a basic unit of heredity, which is found at a specific point on a chromosome

Genetics: the area of biology that focuses on heredity

Genotype: one’s genetic makeup, based on the sequencing of the nucleotides we term A, C, G, and T

Gland: an organ that secretes one or more chemical substances such as hormones, saliva, or milk

Glial cells: cells that remove dead neurons and waste products from the nervous system, nourish and insulate neurons, form myelin, and play a role in neural transmission of messages

Gray matter: the grayish neurons and neural segments that are involved in spinal reflexes

Heredity: the transmission of traits from parent to offspring by means of genes

Hippocampus: a structure of the brain that is involved in memory formation

Hormones: a substance secreted by an endocrine gland that regulates various body functions

Hypothalamus: a bundle of nuclei below the thalamus involved in body temperature, motivation, and emotion

Instinct: a stereotyped pattern of behavior that is triggered by a particular stimulus and nearly identical among members of a species, even when they are reared in isolation

Limbic system: a group of structures involved in memory, motivation, and emotion that forms a fringe along the inner edge of the cerebrum

Magnetic resonance imaging (MRI): an imaging method that places a person in a magnetic field and uses radio waves to cause the brain to emit signals that reveal shifts in the flow of blood, which, when the brain is being scanned, indicate brain activity

Medulla: an oblong area of the hindbrain involved in regulation of heartbeat, blood pressure, movement, and respiration

Monozygotic (MZ) twins: twins that develop from a single fertilized ovum that divides in two early in prenatal development; MZ twins thus share the same genetic code; also called identical twins

Motor cortex: the section of cortex that lies in the frontal lobe, just across the central fissure from the sensory cortex; neural impulses in the motor cortex are linked to muscular responses throughout the body

Mutation: a sudden variation in an inheritable characteristic, as distinguished from a variation that results from generations of gradual selection

Myelin: a fatty substance that encases and insulates axons, facilitating transmission of neural impulses

Natural selection: the concept that holds that adaptive genetic variations among members of a species enable individuals with those variations to survive and reproduce

Nature: the inborn, innate character of an organism

Nerves: a bundle of axons from many neurons

Neural impulses: the electrochemical discharge of a nerve cell or neuron

Neuron: a specialized cell of the nervous system that receives and transmits messages

Neurotransmitters: chemical substances involved in the transmission of neural impulses from one neuron to another

Norepinephrine: a neurotransmitter whose action is similar to that of the hormone epinephrine and that may play a role in depression

Nurture: the sum total of the environmental factors that affect an organism from conception onward

Parasympathetic division: the branch of the ANS that is most active during processes (such as digestion) that restore the body’s reserves of energy

Peripheral nervous system: the part of the nervous system consisting of the somatic nervous system and the autonomic nervous system

Phenotype: one’s actual development and appearance, as based on one’s genotype and environmental influences

Pituitary gland: the gland that secretes growth hormone, prolactin, antidiuretic hormone, and other hormones

Polarize: to ready a neuron for firing by creating an internal negative charge in relation to the body fluid outside the cell membrane

Polygenic: referring to traits that are influenced by combinations of genes

Pons: a structure of the hindbrain involved in respiration, attention, and sleep and arousal

Positron emission tomography (PET): a method of brain imaging that injects a radioactive tracer into the bloodstream and assesses activity of parts of the brain according to the amount of glucose they metabolize

Receptor site: a location on a dendrite of a receiving neuron tailored to receive a neurotransmitter

Refractory period: a phase following firing during which a neuron is less sensitive to messages from other neurons and will not fire

Resting potential: the electrical potential across the neural membrane when it is not responding to other neurons

Reticular formation: a part of the brain involved in attention, sleep, and arousal

Serotonin: a neurotransmitter involved in emotional arousal and sleep; deficiencies of serotonin have been linked to eating disorders, alcoholism, depression, aggression, and insomnia

Sex chromosomes: the 23rd pair of chromosomes, whose genetic material determines the sex of the individual

Somatic nervous system: the division of the peripheral nervous system that connects the central nervous system with sensory receptors, skeletal muscles, and the surface of the body

Somatosensory cortex: the section of cortex in which sensory stimulation is projected; it lies just behind the central fissure in the parietal lobe

Spinal cord: a column of nerves within the spine that transmits messages from sensory receptors to the brain and from the brain to muscles and glands throughout the body

Spinal reflex: a simple, unlearned response to a stimulus that may involve only two neurons

Sympathetic division: the branch of the ANS that is most active during emotional responses, such as fear and anxiety, that spend the body’s reserves of energy

Synapse: a junction between the axon terminals of one neuron and the dendrites or cell body of another neuron

Thalamus: an area near the center of the brain involved in the relay of sensory information to the cortex and in the functions of sleep and attention

Wernicke’s aphasia: a language disorder characterized by difficulty comprehending the meaning of spoken language

White matter: axon bundles that carry messages to and from the brain