GLOSSARY

 

Acetylcholine

A neurotransmitter molecule released at the neuromuscular junction and certain brain synapses

AMPA receptor

A fast-acting non-NMDA glutamate receptor made up of multiple subunits

Amygdala

A small, almond-shaped structure in the medial temporal lobes, involved in the processing of fear and other emotions

Astrocyte

A star-shaped glial cell found in the brain and spinal cord, which supports neurons in various ways and regulates neurochemical transmission. Astrocytes are the most abundant cell type in the brain

Axon

One of two types of nerve fiber, along which nervous impulses are propagated to the nerve terminal (cf. dendrite)

Cell body

The part of the neuron from which the axon and dendrites emerge, containing the nucleus and apparatus for synthesizing proteins

Central nervous system

One of two major subdivisions of the nervous system, consisting of the brain and spinal cord (cf. peripheral nervous system)

Cerebellum

The “little brain,” which plays critical roles in movement, coordination, and motor skill learning, and may also contribute to cognitive functions

Cerebral cortex

The prominent outer region of the brain, which is subdivided into the frontal, temporal, parietal, and occipital lobes

Corpus callosum

The “hard body,” an enormous bundle of nerve fibers connecting the left and right hemispheres of the brain to each other

Dendrite

One of two types of nerve fiber, at which neurons receive chemical signals from other cells (cf. axon)

Dendritic spine

A tiny protruberance on a dendrite that forms the postsynaptic membrane at most excitatory synapses in the brain

DNA

Deoxyribonucleic acid, a double-stranded molecule inside the cell nucleus that carries genetic information

Dopamine

A neurotransmitter, synthesized mostly in the midbrain, that is involved in movement, reward and motivation, and numerous other functions

Electroencephalography (EEG)

A neuroimaging technique that uses scalp electrodes to measure brain waves

Ganglion (pl. ganglia)

A cluster of nerve cells that perform a similar function

Glial cells

A collective term for the various nonneuronal cell types in the nervous system, such as astrocytes, microglia, and oligodendrocytes, that provide nutritional and structural support for neurons and also make vital contributions to information processing

Glutamate

An amino acid that acts as an excitatory neurochemical transmitter through its actions on AMPA, NMDA, and kainate receptors

Gray matter

One of two types of nervous tissue, consisting mostly of nerve cell bodies, which has a dark appearance under the microscope (cf. white matter)

Hippocampus

A region of the medial temporal lobe critical for memory formation

Long-term potentiation (LTP)

A process by which synaptic connections are strengthened, widely thought to be the neural basis of learning and memory

Mesolimbic pathway

The brain’s “reward pathway,” consisting of dopamine-producing neurons in the ventral tegmentum, which project axonal fibers to the nucleus accumbens

Microglia

A type of glial cell that act as the brain’s resident immune cells, clearing away damaged tissues and pathogens, and pruning unwanted synapses

Midbrain

A small but major subdivision of the brain, located in the brain stem, that controls numerous functions, such as eye movements and visual and auditory reflexes, and contains several discrete regions that synthesize dopamine

Myelin

A fatty tissue synthesized by oligodendrocytes that wraps itself around axon fibers and facilitates their propagation of nervous impulses

Nerve terminal

The end of an axon, at which neurotransmitters are released from synaptic vesicles

Nervous impulse

An electrical signal produced by nerve cells, consisting of a reversal of the voltage across the nerve cell membrane, initiated near the cell body and propagated along the axon to the nerve terminal

Neurochemical transmission

The process by which nerve cells communicate with each other, involving the release of neurotransmitter molecules from synaptic vesicles lying beneath the presynaptic membrane, their diffusion across the synapse, and their binding to receptors embedded in the postsynaptic membrane

Neuromuscular junction

The synapse between nerve and muscle, at which motor neurons release acetylcholine

Neuron

A type of brain cell specialized to produce nervous impulses and release neurotransmitters. The human brain contains hundreds, or perhaps thousands, of different types of neurons, most of which have three basic components: a cell body, a single axon fiber, and multiple branched dendrites

Neurotransmitter

A small chemical messenger that nerve cells use to send signals to one another. The brain produces more than one hundred such chemicals, including acetylcholine, dopamine, and serotonin

NMDA receptor

A fast-acting glutamate receptor made up of multiple subunits, which is critical for long-term potentiation (LTP)

Nucleus

A membrane-bound organelle containing genetic instructions stored in the form of DNA molecules

Nucleus accumbens

Part of the brain’s reward system, which assigns value to stimuli according to the amount of dopamine they release

Oligodendrocyte

A type of glial cell, found in the brain and spinal cord, that produces myelin (cf. Schwann cell)

Peripheral nervous system

One of two major subdivisions of the nervous system, consisting of the ganglia and peripheral nerves lying outside the brain and spinal cord (cf. central nervous system)

Postsynaptic membrane

A component of the synapse, containing receptors for neurotransmitter molecules released from the presynaptic membrane

Presynaptic membrane

A component of the synapse, from which neurotransmitter molecules are released

Pruning

The process by which unwanted synapses are eliminated, performed by microglia

Schwann cell

The myelin-forming glial cells of the peripheral nervous system

Serotonin

A monoamine neurotransmitter, synthesized from the amino acid tryptophan, with multiple functions, including the regulation of appetite and mood

Substantia nigra

The “black substance,” a small midbrain nucleus that synthesizes most of the brain’s dopamine

Synapse

The minuscule junction between two nerve cells, measuring just forty billionths of a meter wide, at which neurochemical transmission takes place

Synaptic vesicle

A membrane-bound spherical structure found in nerve terminals, which stores neurotransmitter molecules and releases them into the synaptic cleft in response to a nervous impulse

Transcranial magnetic stimulation

A form of noninvasive brain stimulation that uses magnetic fields to modulate activity in a specified part of the brain

Ventral tegmentum

A region of the midbrain containing neurons that produce the neurotransmitter dopamine, which makes up part of the brain’s reward pathway

White matter

One of two types of tissue in the nervous system, consisting of myelinated nerve fibers and glial cells, which appears white under the microscope