| A | B |
|---|
| Absolute refractory period | The minimum length of time after an action potential during which another action potential cannot begin. |
| Action potential | A brief change in a neuron's electrical charge. |
| Adaptation | An inherited characteristic that increased in a population (through natural selection) because it helped solve a problem of survival or reproduction during the time it emerged. |
| Adoption studies | Research studies that assess hereditary inuence by examining the resemblance between adopted children and both their biological and their adoptive parents. |
| Afferent nerve bers | Axons that carry information inward to the central nervous system from the periphery of the body. |
| Agonist | A chemical that mimics the action of a neurotransmitter. |
| Antagonist | A chemical that opposes the action of a neurotransmitter. |
| Autonomic nervous system (ANS) | The system of nerves that connect to the heart, blood vessels, smooth muscles, and glands. |
| Axon | A long, thin ber that transmits signals away from the neuron cell body to other neurons, or to muscles or glands. |
| Central nervous system (CNS) | The brain and the spinal cord. |
| Cerebral cortex | The convoluted outer layer of the cerebrum. |
| Cerebral hemispheres | The right and left halves of the cerebrum. |
| Cerebrospinal uid (CSF) | A solution that lls the hollow cavities (ventricles) of the brain and circulates around the brain and spinal cord. |
| Chromosomes | Threadlike strands of DNA (deoxyribonucleic acid) molecules that carry genetic information. |
| Corpus callosum | he structure that connects the two cerebral hemispheres. |
| Critical period | A limited time span in the development of an organism when it is optimal for certain capacities to emerge because the organism is especially responsive to certain experiences. |
| Dendrites | Branchlike parts of a neuron that are specialized to receive information. |
| Dominant gene | A gene that is expressed when paired genes are heterozygous (different). |
| Efferent nerve bers | Axons that carry information outward from the central nervous system to the periphery of the body. |
| Electrical stimulation of the brain (ESB) | Sending a weak electric current into a brain structure to stimulate (activate) it. |
| Electroencephalograph (EEG) | A device that monitors the electrical activity of the brain over time by means of recording electrodes attached to the surface of the scalp. |
| Endocrine system | A group of glands that secrete chemicals into the bloodstream that help control bodily functioning. |
| Endorphins | The entire family of internally produced chemicals that resemble opiates in structure and effects. |
| Family studies | Scientic studies in which researchers assess hereditary inuence by examining blood relatives to see how much they resemble each other on a specic trait. |
| Fitness | The reproductive success (number of descendants) of an individual organism relative to the average reproductive success of the population. |
| Forebrain | The largest and most complicated region of the brain, encompassing a variety of structures, including the thalamus, hypothalamus, limbic system, and cerebrum. |
| Fraternal (dizygotic) twins | Twins that result when two eggs are fertilized simultaneously by different sperm cells, forming two separate zygotes. Also called Dizygotic twins. |
| Genes | DNA segments that serve as the key functional units in hereditary transmission. |
| Genetic mapping | The process of determining the location and chemical sequence of specic genes on specic chromosomes. |
| Genotype | A person's genetic makeup. |
| Glia | Cells found throughout the nervous system that provide various types of support for neurons. |
| Heterozygous condition | The situation that occurs when two genes in a specic pair are different. |
| Hindbrain | The part of the brain that includes the cerebellum and two structures found in the lower part of the brainstem: the medulla and the pons. |
| Homozygous condition | The situation that occurs when two genes in a specic pair are the same. |
| Hormones | The chemical substances released by the endocrine glands. |
| Identical (monozygotic) twins | Twins that emerge from one zygote that splits for unknown reasons. Also called Monozygotic twins. |
| Inclusive fitness | The sum of an individual's own reproductive success plus the effects the organism has on the reproductive success of related others. |
| Lesioning | Destroying a piece of the brain. |
| Limbic system | A densely connected network of structures roughly located along the border between the cerebral cortex and deeper subcortical areas. |
| Midbrain | The segment of the brain stem that lies between the hindbrain and the forebrain. |
| Mirror neurons | Neurons that are activated by performing an action or by seeing another monkey or person perform the same action. |
| Myelin sheath | nsulating material, derived from glial cells, that encases some axons of neurons. |
| Natural selection | Principle stating that heritable characteristics that provide a survival reproductive advantage are more likely than alternative characteristics to be passed on to subsequent generations and thus come to be selected over time. |
| Nerves | Bundles of neuron bers (axons) that are routed together in the peripheral nervous system. |
| Neurogenesis | The formation of new neurons in the brain. |
| Neurons | Individual cells in the nervous system that receive, integrate, and transmit information. |
| Neurotransmitters | Chemicals that transmit information from one neuron to another. |
| Parasympathetic division | The branch of the autonomic nervous system that generally conserves bodily resources. |
| Perceptual asymmetries | Left-right imbalances between the cerebral hemispheres in the speed of visual or auditory processing. |
| Peripheral nervous system | All those nerves that lie outside the brain and spinal cord. |
| Phenotype | The ways in which a person's genotype is manifested in observable characteristics. |
| Pituitary gland | The master gland of the endocrine system; it releases a great variety of hormones that fan out through the body, stimulating actions in the other endocrine glands. |
| Polygenic traits | Characteristics that are inuenced by more than one pair of genes. |
| Postsynaptic potential (PSP) | A voltage change at the receptor site on a postsynaptic cell membrane. |
| Recessive gene | A gene whose inuence is masked when paired genes are different (heterozygous). |
| Resting potential | The stable, negative charge of a neuron when it is inactive |
| Reuptake | A process in which neurotransmitters are sponged up from the synaptic cleft by the presynaptic membrane. |
| Soma | The cell body of a neuron; it contains the nucleus and much of the chemical machinery common to most cells. |
| Somatic nervous system | The system of nerves that connect to voluntary skeletal muscles and to sensory receptors. |
| Split-brain surgery | A procedure in which the bundle of bers that connects the cerebral hemispheres (the corpus callosum) is cut to reduce the severity of epileptic seizures. |
| Sympathetic division | The branch of the autonomic nervous system that mobilizes the body's resources for emergencies. |
| Synapse | A junction where information is transmitted from one neuron to the next. |
| Synaptic cleft | A microscopic gap between the terminal button of a neuron and the cell membrane of another neuron. |
| Terminal buttons | Small knobs at the end of axons that secrete chemicals called neurotransmitters. |
| Testosterone | A male sex hormone produced by the testes; women secrete smaller amounts of testosterone from the adrenal cortex and ovary. |
| Transcranial magnetic stimulation (TMS) | A new technique that permits scientists to temporarily enhance or depress activity in a specific area of the brain. |
| Twin studies | A research design in which hereditary inuence is assessed by comparing the resemblance of identical twins and fraternal twins with respect to a trait. |
