Brain Terms

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 neuronıs electrical charge.

Adoption studies
Research studies that assess hereditary influence by examining the resemblance between adopted children and both their biological and their adoptive parents.

Afferent nerve fibers
Axons that carry information inward to the central nervous system from the periphery of the body.

A chemical that mimics the action of a neurotransmitter.

A chemical that opposes the action of a neurotransmitter.

Autonomic nervous system
The system of nerves that connect to the heart, blood vessels, smooth muscles, and glands.

A long, thin fiber that transmits signals away from the neuron cell body to other neurons, or to muscles or glands.

Behavioral genetics
An interdisciplinary field that studies the influence of genetic factors on behavioral traits.

Blood-brain barrier
A semipermeable membrane­like mechanism that stops some chemicals from passing between the bloodstream and the brain.

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.

Cerebral laterality
The degree to which the left or right hemisphere controls various cognitive and behavioral functions.

Cerebrospinal fluid (CSF)
A solution that fills the hollow cavities (ventricles) of the brain and circulates around the brain and spinal cord.

Cerebral laterality
The degree to which the left or right hemisphere controls various cognitive and behavioral functions.

Threadlike strands of DNA (deoxyribonucleic acid) molecules that carry genetic information.

Corpus callosum
he structure that connects the two cerebral hemispheres.

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 fibers
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 theat monitors the electrical activity of the brain over time by means of recording electrodes attached to the surface of the scalp.

Electromyograph (EMG)
A device that records muscular activity and tension.

Endocrine system
A group of glands that secrete chemicals into the bloodstream that help control bodily functioning.

The entire family of internally produced chemicals that resemble opiates in structure and effects.

Excitatory PSP
An electric potential that increases the likelihood that a postsynaptic neuron will fire action potentials.

Family studies
Scientific studies in which researchers assess hereditary influence by examining blood relatives to see how much they resemble each other on a specific trait.

The largest and most complicated region of the brain, encompassing a variety of structures, including the thalamus, hypothalamus, limbic system, and cerebrum.

Fraternal twins
Twins that result when two eggs are fertilized simultaneously by different sperm cells, forming two separate zygotes. Also called Dizygotic twins.

DNA segments that serve as the key functional units in hereditary transmission.

Genetic mapping
The process of determining the location and chemical sequence of specific genes on specific chromosomes.

A personıs genetic makeup.

Cells found throughout the nervous system that provide structural support and insulation for neurons.

A preference for using oneıs right or left hand in most activities.

Heterozygous condition
The situation that occurs when two genes in a specific pair are different.

he 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 specific pair are the same.

The chemical substances released by the endocrine glands.

A structure found near the base of the forebrain that is involved in the regulation of basic biological needs.

Identical twins
Twins that emerge from one zygote that splits for unknown reasons. Also called Monozygotic twins.

Inhibitory PSP
An electric potential that decreases the likelihood that a postsynaptic neuron will fire action potentials.

Neurons that communicate only with other neurons.

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.

The segment of the brain stem that lies between the hindbrain and the forebrain.

Motor neurons
Neurons that carry messages from the nervous system to the muscles that actually move the body.

Myelin sheath
Insulating material, derived from glial cells, that encases some axons of neurons.

Bundles of neuron fibers (axons) that are routed together in the peripheral nervous system.

Chemicals that increase or decrease (modulate) the activity of specific neurotransmitters.

Individual cells in the nervous system that receive, integrate, and transmit information.

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 process.

The ways in which a personıs genotype is manifested in observable characteristics.

Pituitary gland
The ³master gland² 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 influenced 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 influence is masked when paired genes are different (heterozygous).

Resting potential
The stable, negative charge of a neuron when it is inactive.

Sensory neurons
Neurons that receive information from outside the nervous system.

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 fibers that connects the cerebral hemispheres (the corpus callosum) is cut to reduce the severity of epileptic seizures.

Stereotaxic instrument
A device used to implant electrodes at precise locations in the brain.

Sympathetic division
The branch of the autonomic nervous system that mobilizes the bodyıs resources for emergencies.

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.

A structure in the forebrain through which all sensory information (except smell) must pass to get to the cerebral cortex.

Twin studies
A research design in which hereditary influence is assessed by comparing the resemblance of identical twins and fraternal twins with respect to a trait.

A one-celled organism formed by the union of a sperm and an egg.

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