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The science and the art of the brain and nervous system.

Glossary of the neuroscience

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# - A

Neurotransmitter at motor neuron synapses, in autonomic ganglia and a variety of central synapses; binds to two types of receptors—ligand-gated ion channels (nicotinic receptors) and G-protein-coupled receptors (muscarinic receptors).

Loss of color vision as a result of damage to extrastriate visual cortex.

The electrical signal conducted along axons (or muscle fibers) by which information is conveyed from one place to another in the nervous system.

The time-dependent opening of ion channels in response to a stimulus, typically membrane depolarization.

The phenomenon of sensory receptor adjustment to different levels of stimulation; critical for allowing sensory systems to operate over a wide dynamic range.

Membrane-bound enzyme that can be activated by G-proteins to catalyze the synthesis of cyclic AMP from ATP.

see cell adhesion molecules.

see epinephrine.

The central part of the adrenal gland that, under visceral motor stimulation, secretes epinephrine and norepinephrine into the bloodstream.

Refers to synaptic transmission mediated by the release of norepinephrine or epinephrine.

The mature form of an animal, usually defined by the ability to reproduce.

An axon that conducts action potentials from the periphery toward the central nervous system.

The inability to name objects.

Neurons in the ventral horn of the spinal cord that innervate skeletal muscle.

Retinal neurons that mediate lateral interactions between bipolar cell terminals and the dendrites of ganglion cells.

Diminished visual acuity as a result of the failure to establish appropriate visual cortical connections in early life.

The pathological inability to remember or establish memories; retrograde amnesia is the inability to recall existing memories, whereas anterograde amnesia is the inability to lay down new memories.

A synthetically produced central nervous system stimulant with cocaine-like effects; drug abuse may lead to dependence.

The juglike swellings at the base of the semicircular canals that contain the hair cells and cupulae (see also cupulae).

A nuclear complex in the temporal lobe that forms part of the limbic system; its major functions concern autonomic, emotional, and sexual behavior.

A condition in which, due to a defect in the gene that codes for the androgen receptor, testosterone cannot act on its target tissues.

A congenital defect of neural tube closure, in which much of the brain fails to develop.

Loss of the sense of smell.

Toward the front; sometimes used as a synonym for rostral, and sometimes as a synonym for ventral.

A small midline fiber tract that lies at the anterior end of the corpus callosum; like the callosum, it serves to connect the two hemispheres.

Region of the hypothalamus containing nuclei that mediate sexual behaviors; not to be confused with region in rodent called the medial preoptic area, which lies anterior to hypothalamus and also contains nuclei that mediate sexual behavior (most notably the sexually dimorphic nucleus).

A movement or influence acting from the neuronal cell body toward the axonal target.

Ascending sensory pathway in the spinal cord and brainstem that carries information about pain and temperature to the thalamus.

Serum harvested from an animal immunized to an agent of interest.

The inability to comprehend and/or produce language as a result of damage to the language areas of the cerebral cortex (or their white matter interconnections).

Cell death resulting from a programmed pattern of gene expression; also known as “programmed cell death.”]]


The inability to infuse language with its normal emotional content.

One of the three coverings of the brain that make up the meninges; lies between the dura mater and the pia mater.

Loss of reflexes.

Defined by exclusion as those neocortical regions that are not involved in primary sensory or motor processing.

In the hippocampus, the enhancement of a weakly activated group of synapses when a nearby group is strongly activated.

One of the three major classes of glial cells found in the central nervous system; important in regulating the ionic milieu of nerve cells and, in some cases, transmitter reuptake.

A cell surface molecule that causes neurons to adhere to radial glial fibers during neuronal migration.

Slow, writhing movements seen primarily in patients with disorders of the basal ganglia.

Membrane pumps that use the hydrolysis of ATP to translocate ions against their electrochemical gradients.

The physical wasting away of a tissue, typically muscle, in response to disuse or other causes.

The selection of a particular sensory stimulus or mental process for further analysis.

Opening of the external ear canal.

Topographic representation of sound source location, as occurs in the inferior colliculus.

The components of the nervous system (peripheral and central) concerned with the regulation of smooth muscle, cardiac muscle, and glands (see also visceral motor system).

The neuronal process that carries the action potential from the nerve cell body to a target.

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The process by which materials are carried from nerve cell bodies to their terminals (anterograde transport), or from nerve cell terminals to the neuronal cell body (retrograde transport).

Sensory receptors in the visceral motor system that respond to changes in blood pressure.

A group of nuclei lying deep in the subcortical white matter of the frontal lobes that organize motor behavior. The caudate and putamen and the globus pallidus are the major components of the basal ganglia; the subthalamic nucleus and substantia nigra are often included.

A thin layer of extracellular matrix material (primarily collagen, laminin, and fibronectin) that surrounds muscle cells and Schwann cells. Also underlies all epithelial sheets.

The membrane that forms the floor of the cochlear duct, on which the cochlear hair cells are located.

Inhibitory interneurons in the cerebellar cortex whose cells bodies are located within the Purkinje cell layer and whose axons make basketlike terminal arbors around Purkinje cell bodies.

Referring to both eyes.

The bioactive amine neurotransmitters; includes the catecholamines (epinephrine, norepinephrine, dopamine), serotonin, and histamine.

Retinal neurons that provide a direct link between photoreceptor terminals and ganglion cell dendrites.

Sexual attraction to members of both the opposite and the same phenotypic sex.

A cell produced when the egg undergoes cleavage.

An early embryo during the stage when the cells are typically arranged to form a hollow sphere.

The region of visual space that falls on the optic disk; due to the lack of photoreceptors in the optic disk, objects that lie completely within the blind spot are not perceived.

A diffusion barrier between the brain vasculature and the substance of the brain formed by tight junctions between capillary endothelial cells.

A swelling specialized for the release of neurotransmitter that occurs along or at the end of an axon.

Pathologically slow movement.

One member of a family of neutrophic factors, the best-known constituent of which is nerve growth factor.

The portion of the brain that lies between the diencephalon and the spinal cord; comprises the midbrain, pons, and medulla.

Difficulty producing speech as a result of damage to Broca’s area in the left frontal lobe.

An area in the left frontal lobe specialized for the production of language.

A region of the hippocampus that shows a robust form of long-term potentiation.

A region of the hippocampus containing the neurons that form the Schaffer collaterals.

A family of calcium-dependent cell adhesion molecules found on the surfaces of growth cones and the cells over which they grow.

The major sulcus on the medial aspect of the occipital lobe; the primary visual cortex lies largely within this sulcus.

A protein activated by cyclic AMP that binds to specific regions of DNA, thereby increasing the transcription rates of nearby genes.

Specific DNA sequences that bind transcription factors activated by cAMP (see also cAMP response element binding protein).

Specialized tissue masses found at the bifurcation of the carotid arteries in humans and other mammals that respond to the chemical composition of the blood (primarily the partial pressure of oxygen and carbon dioxide).

A term referring to molecules containing a catechol ring and an amino group; examples are the neurotransmitters epinephrine, norepinephrine, and dopamine.

The collection of segmental ventral and dorsal roots that extend from the caudal end of the spinal cord to their exit from the spinal canal.

Posterior, or “tailward.

One of the three major components of the basal ganglia (the other two are the globus pallidus and putamen).

A family of molecules on cell surfaces that cause them to stick to one another (see also fibronectin and laminin).

The brain and spinal cord of vertebrates (by analogy, the central nerve cord and ganglia of invertebrates).

Oscillatory spinal cord or brainstem circuits responsible for programmed, rhythmic movements such as locomotion.

A major sulcus on the lateral aspect of the hemispheres that forms the boundary between the frontal and parietal lobes. The anterior bank of the sulcus contains the primary motor cortex; the posterior bank contains the primary sensory cortex.

A pathological inability to make coordinated movements associated with lesions to the cerebellum.

The superficial gray matter of the cerebellum.

The three bilateral pairs of axon tracts (inferior, middle, and superior cerebellar peduncles) that carry information to and from the cerebellum.

Prominent hindbrain structure concerned with motor coordination, posture, and balance. Composed of a three-layered cortex and deep nuclei; attached to the brainstem by the cerebellar peduncles.

The portion of the ventricular system that connects the third and fourth ventricles.

The superficial gray matter of the cerebral hemispheres.

The major fiber bundles that connect the brainstem to the cerebral hemispheres.

The part of the cerebellar cortex that receives input from the cerebral cortex via axons from the pontine relay nuclei.

A normally clear and cell-free fluid that fills the ventricular system of the central nervous system; produced by the choroid plexus in the third ventricle.

The largest and most rostral part of the brain in humans and other mammals, consisting of the two cerebral hemispheres.

Cellular Feline Osteosarcoma gene product; a transcription factor that binds as a heterodimer, thus activating gene transcription.

Synapses that transmit information via the secretion of chemical signals (neurotransmitters).

The idea that nerve cells bear chemical labels that determine their connectivity.

The movement of a cell up (or down) the gradient of a chemical signal.

The growth of a part of a cell (axon, dendrite, filopodium) up (or down) a chemical gradient.

An experimentally generated embryo (or organ) comprising cells derived from two or more species (or other genetically distinct sources).

Referring to synaptic transmission mediated by acetylcholine.

Jerky, involuntary movements of the face or extremities associated with damage to the basal ganglia.

The combination of jerky, ballistic, and writhing movements that characterizes the late stages of Huntington’s disease.

Specialized epithelium in the ventricular system that produces cerebrospinal fluid.

Nuclear organelle that bears the genes.

Circular band of muscle surrounding the lens; contraction allows the lens to round up during accommodation.

Cortex of the cingulate gyrus that surrounds the corpus callosum; important in emotional and visceral motorbehavior.

Prominent gyrus on the medial aspect of the hemisphere, lying just superior to the corpus callosum; forms a part of the limbic system.

Prominent sulcus on the medial aspect of the hemisphere.

Variations in physiological functions that occur on a daily basis.

Arterial anastomosis on the ventral aspect of the midbrain; connects the posterior and anterior cerebral circulation.

Large, cerebrospinal-fluid-filled spaces that lie within the subarachnoid space.

A taxonomic category subordinate to phylum; comprises animal orders.

Axons that originate in the inferior olive, ascend through the inferior cerebellar peduncle, and make terminalarborizations that invest the dendritic tree of Purkinje cells.

The progeny of a single cell.

The coiled structure within the inner ear where vibrations caused by sound are transduced into neural impulses.

A general term referring to higher order mental processes; the ability of the central nervous system to attend, identify, and act on complex stimuli.

A molecule that causes collapse of growth cones; a member of the semaphorin family of signaling molecules.

The two paired hillocks that characterize the dorsal surface of the midbrain; the superior colliculi concern vision, the inferior colliculi audition.

The struggle among nerve cells, or nerve cell processes, for limited resources essential to survival or growth.

A component of the external ear.

Difficulty producing speech as a result of damage to the connection between Wernicke’s and Broca’s language areas.

The speed at which an action potential is propagated along an axon.

Diminished sense of hearing due reduced ability of sounds to be mechanically transmitted to the inner ear. Common causes include occlusion of the ear canal, perforation of the tympanic membrane, and arthritic degeneration of the middle ear ossicles. Contrast with sensorineural hearing loss.

The three distinct photopigments found in cones; the basis for color vision.

Photoreceptors specialized for high visual acuity and the perception of color.

Genetic deficiency that leads to overproduction of androgens and a resultant masculinization of external genitalia in genotypic females.

The paired movements of the two eyes in the same direction, as occurs in the vestibulo-ocular reflex (see also vergence movements and vestibulo-ocular reflex).

Fellow member of a species.

On the other side.

Neurological condition in which the patient does not acknowledge or attend to the left visual hemifield or the left half of the body. The syndrome typically results from lesions of the right parietal cortex.

The difference, usually expressed in terms of a percentage in luminance, between two territories in the visual field(can also apply to color when specified as spectral contrast).

Innervation of a target cell by axons from more than one neuron.

The transparent surface of the eyeball in front of the lens; the major refractive element in the optical pathway.

Referring to a plane through the brain that runs parallel to the coronal suture (the mediolateral plane). Synonymous with frontal plane.

The large midline fiber bundle that connects the cortices of the two cerebral hemispheres.

General term applied to the caudate and putamen; name derives from the striated appearance of these basal ganglianuclei in sections of fresh material.

The superficial mantle of gray matter covering the cerebral hemispheres and cerebellum, where most of the neurons in the brain are located.

Connections made between cortical areas in the same hemisphere or betweem the two hemispheres via the cerebral commissures (the corpus callosum and the anterior commissure).

Pathway carrying motor information from the primary and secondary motor cortices to the brain stem and spinal cord.

Two or more types of neurotransmitters within a single synapse; may be packaged into separate populations of synaptic vesicles or co-localized within the same synaptic vesicles.

The sensory ganglia associated with the cranial nerves; these correspond to the dorsal root ganglia of the spinal segmental nerves.

Nuclei in the brainstem that contain the neurons related to cranial nerves III–XII.

The 12 pairs of nerves arising from the brainstem that carry sensory information toward (and sometimes motorinformation away from) the central nervous system.

see cAMP response element binding protein.

The hair cell-containing sensory epithelium of the semicircular canals.

A restricted developmental period during which the nervous system is particularly sensitive to the effects of experience.

Sensory relay nuclei that lie in the lower medulla; they contain the second-order sensory neurons that relay mechanosensory information from peripheral receptors in the upper body to the thalamus.

Gelatinous structures in the semicircular canals in which the hair cell bundles are embedded.

Distinct regions of the neocortical mantle identified by differences in cell size, packing density, and laminar arrangement.

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Excessive tone in extensor muscles as a result of damage to descending motor pathways at the level of the brainstem.

Memories available to consciousness that can be expressed by language.

A crossing of fiber tracts in the midline.

The nuclei at the base of the cerebellum that relay information from the cerebellar cortex to the thalamus.

Genes that are synthesized de novo after a cell is stimulated; usually refers to transcriptional activator proteins that are synthesized after preexisting transcription factors are first activated by an inducing stimulus.

A behavioral paradigm used to test cognition and memory.

Slow (<4 Hz) electroencephalographic waves that characterize stage IV (slow-wave) sleep.

A neuronal process arising from the cell body that receives synaptic input.

Removal of the innervation to a target.

A region of the hippocampus; so named because it is shaped like a tooth.

The displacement of a cell’s membrane potential toward a less negative value.

The area of skin supplied by the sensory axons of a single spinal nerve.

Commitment of a developing cell or cell group to a particular fate.

Referring to the majority of mammals (and most color-blind humans), which have only two instead of three cone pigments to mediate color vision.

Portion of the brain that lies just rostral to the midbrain; comprises the thalamus and hypothalamus.

The progressive specialization of developing cells.

A more potent form of testosterone that masculinizes the external genitalia.

Arrangement of inhibitory and excitatory cells in a circuit that generates excitation by the transient inhibition of a tonically active inhibitory neuron.

Movements of the two eyes in opposite directions (see also vergence movements).

Farther away from a point of reference (the opposite of proximal).

The branching of an axon to innervate multiple target cells.

A catecholamine neurotransmitter.

Referring to the back.

Second-order sensory neurons in the lower medulla that relay mechanosensory information from the spinal cord to the thalamus; comprises the cuneate and gracile nuclei.

Major ascending tracts in the spinal cord that carry mechanosensory information from the first-order sensoryneurons in dorsal root ganglia to the dorsal column nuclei; also called the posterior funiculi.

The dorsal portion of the spinal cord gray matter; contains neurons that process sensory information.

The segmental sensory ganglia of the spinal cord; contain the first-order neurons of the dorsal column/medial lemniscus and spinothalamic pathways.

The bundle of axons that runs from the dorsal root ganglia to the dorsal horn of the spinal cord, carrying sensoryinformation from the periphery.

The thick external covering of the brain and spinal cord; one of the three components of the meninges, the other two being the pia mater and arachnoid mater.

A class of endogenous opioid peptides.

Difficulty producing speech as a result of damage to the primary motor centers that govern the muscles of articulation; distinguished from aphasia, which results from cortical damage.

Inaccurate movements due to faulty judgment of distance. Characteristic of cerebellar pathology.

Lack of muscle tone.

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The initial electrical current, measured in voltage clamp experiments, that results from the voltage-dependent entry of a cation such as Na+ or Ca2+; produces the rising phase of the action potential.

The most superficial of the three embryonic germ layers; gives rise to the nervous system and epidermis.

Midbrain nucleus containing the autonomic neurons that constitute the efferent limb of the pupillary light reflex.

An axon that conducts information away from the central nervous system.

Synapses that transmit information via the direct flow of electrical current at gap junctions.

The condition in which no net ionic flux occurs across a membrane because ion concentration gradients and opposing transmembrane potentials are in exact balance.

Capable of generating an electrical current; usually applied to membrane transporters that create electrical currents while translocating ions.

The developing organism before birth or hatching.

Postsynaptic current produced by neurotransmitter release and binding at the motor end plate.

Depolarization of the membrane potential of skeletal muscle fiber, caused by the action of the transmitteracetylcholine at the neuromuscular synapse.

Referring to the release of signaling molecules whose effects are made widespread by distribution in the general circulation.

A budding off of vesicles from the plasma membrane, which allows uptake of materials in the extracellular medium.

The innermost of the three embryonic germ layers.

Peptides in the central nervous system that have the same pharmacological effects as morphine and other derivatives of opium.

The potassium-rich fluid filling both the cochlear duct and the membranous labyrinth; bathes the apical end of the hair cells.

One of a group of neuropeptides that are agonists at opioid receptors, virtually all of which contain the sequence Tyr-Gly-Gly-Phe.

The complex postsynaptic specialization at the site of nerve contact on skeletal muscle fibers.

The term used to indicate the physical basis of a stored memory.

A general term for endogenous opioid peptides.

The epithelial lining of the canal of the spinal cord and the ventricles.

Epithelial cells that line the ventricular system.

The outermost layer of the skin; derived from the embryonic ectoderm.

Referring to influences on development that arise from factors other than genetic instructions.

Catecholamine hormone and neurotransmitter that binds to α- and β-adrenergic G-protein-coupled receptors.

The connective tissue surrounding axon fascicles of a peripheral nerve.

Any continuous layer of cells that covers a surface or lines a cavity.

The membrane potential at which a given ion is in electrochemical equilibrium.

One of the biologically important C18 class of steroid hormones capable of inducing estrous in females.

An organism that contains cells with nuclei.

Neurotransmitter-induced postsynaptic potential change that depolarizes the cell, and hence increases the likelihood of initiating a postsynaptic action potential.

A form of cell secretion resulting from the fusion of the membrane of a storage organelle, such as a synaptic vesicle, with the plasma membrane.

A piece of tissue maintained in culture medium.

A subdivision of the globus pallidus.

A matrix composed of collagen, laminin, and fibronectin that surrounds most cells (see also basal lamina).

Fibers of skeletal muscles; a term that distinguishes ordinary muscle fibers from the specialized intrafusal fibers associated with muscle spindles.

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Neurons in the temporal cortex of rhesus monkeys that respond specifically to faces.

The increased transmitter release produced by an action potential that follows closely upon a preceding action potential.

A taxonomic category subordinate to order; comprises genera.

The aggregation of neuronal processes to form a nerve bundle; also refers to the spontaneous discharge of motorunits after muscle denervation.

A protein that actively sequestors circulating estrogens.

The developing mammalian embryo at relatively late stages when the parts of the body are recognizable.

Spontaneous contractile activity of denervated muscle fibers.

A peptide growth factor, originally defined by its mitogenic effects on fibroblasts; also acts as an inducer during early brain development.

A large cell adhesion molecule that binds integrins.

Slender protoplasmic projection, arising from the growth cone of an axon or a dendrite, that explores the local environment.

A deep cleft in the brain; distinguished from sulci, which are shallower cortical infoldings.

Polysynaptic reflex mediating withdrawal from a painful stimulus.

Region in the ventral portion of the developing spinal cord; important in the guidance and crossing of growing axons.

The name given to the gyral formations of the cerebellum.

The anterior portion of the brain that includes the cerebral hemispheres (includes the telencephalon and diencephalon).

An axon tract, best seen from the medial surface of the divided brain, that interconnects the hypothalamus and hippocampus.

The ventricular space that lies between the pons and the cerebellum.

Area of the retina specialized for high acuity in the center of the macula; contains a high density of cones and few rods.

Capillary and rod-free zone in the center of the fovea.

One of the four lobes of the brain; includes all the cortex that lies anterior to the central sulcus and superior to the lateral fissure.

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A large family of neurotransmitter or hormone receptors, characterized by seven transmembrane domains; the binding of these receptors by agonists leads to the activation of intracellular G-proteins.

Term for two large groups of proteins—the heterotrimeric G-proteins and the small-molecule G-proteins—that can be activated by exchanging bound GDP for GTP.

Class of spinal motor neurons specifically concerned with the regulation of muscle spindle length; these neurons innervate the intrafusal muscle fibers of the spindle.

Collections of hundreds to thousands of neurons found outside the brain and spinal cord along the course of peripheral nerves.

A neuron located in a ganglion.

A specialized intercellular contact formed by channels that directly connect the cytoplasm of two cells.

The early embryo during the period when the three embryonic germ layers are formed; follows the blastula stage.

The cell movements (invagination and spreading) that transform the embryonic blastula into the gastrula.

Self-perception of one’s alignment with the traits associated with being a phenotypic female or male in a given culture.

A hereditary unit located on the chromosomes; genetic information is carried by linear sequences of nucleotides in DNA that code for corresponding sequences of amino acids.

The complete set of an animal’s genes.

The genetic makeup of an individual.

Sexual characterization according to the complement of sex chromosomes; XX is a genotypic female, and XY is a genotypic male.

A taxonomic division that comprises a number of closely related species within a family.

The egg or sperm (or the precursors of these cells).

The three primary layers of the developing embryo from which all adult tissues arise: ectoderm, mesoderm, and endoderm.

The support cells associated with neurons (astrocytes, oligodendrocytes, and microglia in the central nervous system; Schwann cells in peripheral nerves; and satellite cells in ganglia).

One of the three major nuclei that make up the basal ganglia in the cerebral hemispheres; relays information from the caudate and putamen to the thalamus.

Characteristic collections of neuropil in the olfactory bulbs; formed by dendrites of mitral cells and terminals of olfactory receptor cells, as well as processes from local interneurons.

A metabolic cycle of glutamate release and resynthesis involving both neuronal and glial cells.

A G-protein found uniquely in olfactory receptor neurons.

Receptors located in muscle tendons that provide mechanosensory information to the central nervous system about muscle tension.

Sensory nuclei in the lower medulla; these second-order sensory neurons relay mechanosensory information from the lower body to the thalamus.

A systematic variation of the concentration of a molecule (or some other agent) that influences cell behavior.

The layer of the cerebellar cortex where granule cell bodies are found. Also used to refer to cell-rich layers in neocortex and hippocampus.

General term that describes regions of the central nervous system rich in neuronal cell bodies and neuropil; includes the cerebral and cerebellar cortices, the nuclei of the brain, and the central portion of the spinal cord.

The specialized end of a growing axon (or dendrite) that generates the motive force for elongation.

The ridges of the infolded cerebral cortex (the valleys between these ridges are called sulci).

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The sensory cells within the inner ear that transduce mechanical displacement into neural impulses.

The opening at the apex of the cochlea that joins the scala vestibuli and scala tympani.

see primitive pit.

A large group of proteins consisting of three subunits (α, β, and γ) that can be activated by exchanging bound GDP with GTP resulting in the liberation of two signaling molecules—αGTP and the βg-dimer.

Neurons that are relatively remote from peripheral targets.

see rhombencephalon.

A cortical structure in the medial portion of the temporal lobe; in humans, concerned with short-term declarative memory, among many other functions.

A biogenic amine neurotransmitter derived from the amino acid histidine.

A set of master control genes whose expression establishes the early body plan of developing organisms (see also homeotic mutant).

A mutation that transforms one part of the body into another (e.g., insect antennae into legs). Affects homeobox genes.

Technically, referring to structures in different species that share the same evolutionary history; more generally, referring to structures or organs that have the same general anatomy and perform the same function.

Sexual attraction to an individual of the same phenotypic sex.

Retinal neurons that mediate lateral interactions between photoreceptor terminals and the dendrites of bipolar cells.

A plant enzyme widely used to stain nerve cells (after injection into a neuron, it generates a visible precipitate by one of several histochemical reactions).

An autosomal dominant genetic disorder in which a single gene mutation results in personality changes, progressive loss of the control of voluntary movement, and eventually death. Primary target is the basal ganglia.

Enlarged cranium as a result of increased cerebrospinal fluid pressure (typically due to a mechanical outflow blockage).

Increased perception of pain.

Excessive movement.

The displacement of a cell’s membrane potential toward a more negative value.

A paucity of movement.

A collection of small but critical nuclei in the diencephalon that lies just inferior to the thalamus; governs reproductive, homeostatic, and circadian functions.

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A rapid and permanent form of learning that occurs in response to early experience.

The time-dependent closing of ion channels in response to a stimulus, such as membrane depolarization.

Chemical signals originating from one set of cells that influence the differentiation of other cells.

The ability of a cell or tissue to influence the fate of nearby cells or tissues during development by chemical signals.

Paired hillocks on the dorsal surface of the midbrain; concerned with auditory processing.

Prominent nucleus in the medulla; a major source of input to the cerebellum.

The connection between the hypothalamus and the pituitary gland; also known as the pituitary stalk.

Neurotransmitter-induced postsynaptic potential change that tends to decrease the likelihood of a postsynaptic action potential.

Establish synaptic contact with a target.

Referring to all the synaptic contacts of a target.

The innervation of a target cell by a particular axon; more loosely, the innervation of a target.

The developmental process by which the number of axons innervating some classes of target cells is diminished.

A developmental influence that dictates the fate of a cell rather than simply permitting differentiation to occur.

The portion of the cerebral cortex that is buried within the depths of the lateral fissure.

Proteins that possess hydrophobic domains that are inserted into membranes.

The summation of excitatory and inhibitory synaptic conductance changes by postsynaptic cells.

A family of receptor molecules found on growth cones that bind to cell adhesion molecules such as laminin and fibronection.

Tremor that occurs while performing a voluntary motor act. Characteristic of cerebellar pathology.

Mechanosensory pathway in the brainstem that runs from the dorsal column nuclei to form the medial lemniscus.

Large white matter tract that lies between the diencephalon and the basal ganglia; contains, among others, sensoryaxons that run from the thalamus to the cortex and motor axons that run from the cortex to the brainstem and spinal cord.

Technically, a neuron in the pathway between primary sensory and primary effector neurons; more generally, a neuron that branches locally to innervate other neurons.

Four cell groups located slightly lateral to the third ventricle in the anterior hypothalamus of primates; thought to play a role in sexual behavior.

Specialized muscle fibers found in muscle spindles.

An animal without a backbone (includes about 97% of extant animals).

Referring to any biological process studied outside of the organism (literally, “in glass”).

Referring to any biological process studied in an intact living organism (literally “in life”).

Integral membrane proteins possessing pores that allow certain ions to diffuse across cell membranes, thereby conferring selective ionic permeability.

Membrane transporters that translocate one or more ions against their concentration gradient by using the electrochemical gradient of other ions as an energy source.

Receptors in which the ligand binding site is an integral part of the receptor molecule.

see transporters.

On the same side of the body.

Circular pigmented membrane behind the cornea; perforated by the pupil.

Insufficient blood supply.

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A true ciliary structure which, along with the stereocilia, comprises the hair bundle of vestibular and fetal cochlear hair cells in mammals (it is not present in the adult mammalian cochlear hair cell).

An amnesic syndrome seen in chronic alcoholics.


Referring to the internal ear; comprises the cochlea, vestibular apparatus, and the bony canals in which these structures are housed.

The leading edge of a motile cell or growth cone, which is rich in actin filaments.

Cell layers that characterize the neocortex, hippocampus, and cerebellar cortex. The gray matter of the spinal cordis also arranged in laminae.

A large cell adhesion molecule that binds integrins.

The delayed electrical current, measured in voltage clamp experiments, that results from the voltage-dependent efflux of a cation such as K+. Produces the repolarizing phase of the action potential.

The lateral regions of spinal cord white matter that convey motor information from the brain to the spinal cord.

The cleft on the lateral surface of the brain that separates the temporal and frontal lobes.

A nucleus in the thalamus that receives the axonal projections of retinal ganglion cells in the primary visual pathway.

The projection from the olfactory bulbs to higher olfactory centers.

A thalamic nucleus that receives its major input from sensory and association cortices and projects in turn to association cortices, particularly in the parietal and temporal lobes.

The auditory brainstem structure that processes interaural intensity differences and, in humans, mediates sound localization for stimuli greater than 3 kHz.

The acquisition of novel behavior through experience.

Transparent structure in the eye whose thickening or flattening in response to visceral motor control allows light rays to be focused on the retina.

The quality of associating a symbol (e.g., a word) with a particular object, emotion, or idea.

Dictionary. Sometimes used to indicate region of brain that stores the meanings of words.

Term for a large group of neurotransmitter receptors that combine receptor and ion channel functions into a single molecule.

The limb rudiment of vertebrate embryos.

Cortex that lies superior to the corpus callosum on the medial aspect of the cerebral hemispheres; forms the cortical component of the limbic system.

Term that refers to those cortical and subcortical structures concerned with the emotions; the most prominent components are the cingulate gyrus, the hippocampus, and the amygdala.

The four major divisions of the cerebral cortex (frontal, parietal, occipital, and temporal).

General term referring to neurons whose activity mediates interactions between sensory systems and motorsystems; interneuron is often used as a synonym.

A small brainstem nucleus with widespread adrenergic cortical and descending connections; important in the governance of sleep and waking.

Lasting days, weeks, months, or longer.

A persistent weakening of synapses based on recent patterns of activity.

Memories that last days, weeks, months, years, or a lifetime.

A persistent strengthening of synapses based on recent patterns of activity.

Spinal motor neuron; directly innervates muscle (also referred to as α or primary motor neuron).

Signs and symptoms arising from damage to α motor neurons; these include paralysis or paresis, muscle atrophy, areflexia, and fibrillations.

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Visible with the naked eye.

Ionic currents flowing through large numbers of ion channels distributed over a substantial area of membrane.

The central region of the retina that contains the fovea (the term derives from the yellowish appearance of this region in ophthalmoscopic examination); also, the sensory epithelia of the otolith organs.

A component of the primary visual pathway specialized for the perception of motion; so named because of the relatively large cells involved.

An animal the embyros of which develop in a uterus and the young of which begin to suckle at birth (technically, a member of the class Mammalia).

Small prominences on the ventral surface of the diencephalon; functionally, part of the caudal hypothalamus.

The ordered projection of axons from one region of the nervous system to another, by which the organization of the body (or some function) is reflected in the organization of the nervous system.

Receptors specialized to sense mechanical forces.

Located nearer to the midsagittal plane of an animal (the opposite of lateral).

A thalamic nucleus that receives its major input from sensory and association cortices and projects in turn to association cortices, particularly in the frontal lobe.

The major thalamic relay for auditory information.

Axon tract in the brainstem that carries mechanosensory information from the dorsal column nuclei to the thalamus.

Axon tract that carries excitatory projections from the abducens nucleus to the contralateral oculomotor nucleus; important in coordinating conjugate eye movements.

The auditory brainstem structure that processes interaural time differences and serves to compute the horizontal location of a sound source.

The principal projection neuron of the caudate and putamen.

The caudal portion of the brainstem, extending from the pons to the spinal cord.

Longitudinal bulges on the ventral aspect of the medulla that signify the corticospinal tracts at this level of the neuraxis.

Encapsulated cutaneous mechanosensory receptors specialized for the detection of fine touch and pressure.

The reciprocal of membrane resistance. Changes in membrane conductance result from, and are used to describe, the opening or closing of ion channels.

The external covering of the brain; includes the pia, arachnoid, and dura mater.

Encapsulated cutaneous mechanosensory receptors specialized for the detection of fine touch and pressure.

see midbrain.

The middle of the three germ layers; gives rise to muscle, connective tissue, skeleton, and other structures.

Light levels at which both the rod and cone systems are active.

Refers to receptors that are indirectly activated by the action of neurotransmitters or other extracellular signals, typically through the aegis of G-protein activation.

That part of the optic radiation that runs in the caudal portion of the temporal lobe.

One of the three main types of central nervous system glia; concerned primarily with repairing damage following neural injury.

Ionic currents flowing through single ion channels.

The most rostral portion of the brainstem; identified by the superior and inferior colliculi on its dorsal surface, and the cerebral penduncles on its ventral aspect.

Large white matter tract that carries axons from the pontine relay nuclei to the cerebellar cortex.

Small, spontaneous depolarization of the membrane potential of skeletal muscle cells, caused by the release of a single quantum of acetylcholine.

The major output neurons of the olfactory bulb.

Having to do with memory.

A category of function. For example, vision, hearing, and touch are different sensory modalities.

The layer of the cerebellar cortex containing the apical dendrites of Purkinje cells, parallel fibers from granule cells, a few local circuit neurons, and the synapses between these elements.

An antibody molecule raised from a clone of transformed lymphocytes.

A plant alkaloid that gives opium its analgesic properties.

A molecule that influences morphogenesis.

The generation of animal form.

The study of the form and structure of organisms; or, more commonly, the form and structure of an animal or animal part.

Pertaining to movement.

The region of the cerebral cortex lying anterior to the central sulcus concerned with motor behavior; includes the primary motor cortex in the precentral gyrus and associated cortical areas in the frontal lobe.

By usage, a nerve cell that innervates skeletal muscle. Also called primary or α motor neuron.

The collection of motor neurons that innervates a single muscle.

A broad term used to describe all the central and peripheral structures that support motor behavior.

A motor neuron and the skeletal muscle fibers it innervates; more loosely, the collection of skeletal muscle fibers innervated by a single motor neuron.

Term referring the mucus membranes lining the nose, mouth, gut, and other epithelial surfaces.

A group of G-protein-coupled acetylcholine receptors activated by the plant alkaloid muscarine.

Highly specialized sensory organ found in most skeletal muscles; provides mechanosensory information about muscle length.

The normal, ongoing tension in a muscle; measured by resistance of a muscle to passive stretching.

The multilaminated wrapping around many axons formed by oligodendrocytes or Schwann cells.

Process by which glial cells wrap axons to form multiple layers of glial cell membrane that increase axonal conduction velocity.

A fundamental spinal reflex that is generated by the motor response to afferent sensory information arising from muscle spindles.

The part of each somite that contributes to the development of skeletal muscles.

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A type of ATPase transporter in the plasma membrane of most cells that is responsible for accumulating intracellular K+ and extruding intracellular Na+.

Referring to the region of the visual field of each eye in the direction of the nose.

Reflexive response induced by changing binocular fixation to a closer target; includes convergence, accommodation, and pupillary constriction.

The six-layered cortex that forms the surface of most of the cerebral hemispheres.

A mathematical relationship that predicts the equilibrium potential across a membrane that is permeable to only one ion.

A collection of peripheral axons that are bundled together and travel a common route.

A neurotrophic protein required for survival and differentiation of sympathetic ganglion cells and certain sensoryneurons. Preeminent member of the neurotrophin family of growth factors.

A family of diffusible molecules that act as attractive or repulsive cues to guide growing axons.

Molecule that helps bind axons together and is widely distributed in the developing nervous system. Structurally related to immunoglobin.

A group of progenitor cells that forms along the dorsum of the neural tube and gives rise to peripheral neurons and glia (among other derivatives).

The thickened region of the dorsal ectoderm of a neurula that gives rise to the neural tube.

The primordium of the brain and spinal cord; derived from the neural ectoderm.

A neuronal branch (usually used when the process in question could be either an axon or a dendrite, such as the branches of isolated nerve cells in tissue culture).

A dividing cell, the progeny of which develop into neurons.

The development of the nervous system.

see glia.

A group of antipsychotic agents that cause indifference to stimuli by blocking brain dopamine receptors.

A segment of the rhombencephalon (synonym for rhombomere).

The synapse made by a motor axon on a skeletal muscle fiber.

Cell specialized for the conduction and transmission of electrical signals in the nervous system.

The spatial arrangement of neuronal branches.

A cell adhesion molecule, structurally related to immunoglobin molecules, that promotes adhesive interactions between neurons and glia.

A general term describing a large number of peptides that function as neurotransmitters or neurohormones.

The dense tangle of axonal and dendritic branches, and the synapses between them, that lies between neuronal cell bodies in the gray matter of the brain and spinal cord.

Substance released by synaptic terminals for the purpose of transmitting information from one nerve cell to another.

A general term for molecules that promote the growth and survival of neurons.

The idea that developing neurons compete for a limited supply of trophic factors secreted by their targets.

A family of trophic factor molecules that promote the growth and survival of several different classes of neurons.

The early vertebrate embryo during the stage when the neural tube forms from the neural plate; follows the gastrulastage.

The process by which the neural plate folds to form the neural tube.

Cutaneous and subcutaneous receptors (usually free nerve endings) specialized for the detection of harmful (noxious) stimuli.

Periodic gaps in the myelination of axons where action potentials are generated.

Collectively, those phases of sleep characterized by the absence of rapid eye movements.

Catecholamine hormone and neurotransmitter that binds to α- and β-adrenergic receptors, both of which are G-protein-coupled receptors.

A transient, cylindrical structure of mesodermal cells underlying the neural plate (and later the neural tube) in vertebrate embryos. Source of important inductive signals for spinal cord.

Collection of nerve cells in the brain that are anatomically discrete, and which typically serve a particular function.

Region of the dorsal horn of the spinal cord that receives information from nociceptors.

Literally, a nodding movement. Refers to repetitive movements of the eyes normally elicited by large-scale movements of the visual field (optokinetic nystagmus). Nystagmus in the absence of appropriate stimuli usually indicates brainstem or cerebellar pathology.


The posterior lobe of the cerebral hemisphere; primarily devoted to vision.

The segregated termination patterns of thalamic inputs representing the two eyes in primary visual cortex of some mammalian species.

Molecules capable of eliciting responses from receptors in the olfactory mucosa.

Olfactory relay station that receives axons from cranial nerve I and transmits this information via the olfactory tract to higher centers.

Pseudostratified epithelium that contains olfactory receptor cells, supporting cells, and mucus-secreting glands.

Bipolar neurons in olfactory epithelium that contain receptors for odorants.

see lateral olfactory tract.

One of three classes of central neuroglial cells; their major function is to elaborate myelin.

The developmental history of an individual animal; also used as a synonym for development.

Sexually dimorphic nucleus in the human spinal cord that innervates striated perineal muscles mediating contraction of the bladder in males, and vaginal constriction in females.

Any natural or synthetic drug that has pharmacological actions similar to those of morphine.

Proteins in photoreceptors that absorb light (in humans, rhodopsin and the three specialized cone opsins).

The junction of the two optic nerves on the ventral aspect of the diencephalon, where axons from the nasal parts of each retina cross the midline.

see optic vesicle.

The region of the retina where the axons of retinal ganglion cells exit to form the optic nerve.

The nerve (cranial nerve II) containing the axons of retinal ganglion cells; extends from the eye to the optic chiasm.

Portion of the internal capsule that comprises the axons of lateral geniculate neurons that carry visual information to the striate cortex.

The first central station in the visual pathway of many vertebrates (analogous to the superior colliculus in mammals).

The axons of retinal ganglion cells after they have passed through the region of the optic chiasm en route to the lateral geniculate nucleus of the thalamus.

The evagination of the forebrain vesicle that generates the retina and induces lens formation in the overlying ectoderm.

Movements of the eyes that compensate for head movements; the stimulus for optokinetic movements is large-scale motion of the visual field.

Repeated reflexive responses of the eyes to ongoing large-scale movements of the visual scene.

Division of the prefrontal cortex that lies above the orbits in the most rostral and ventral extension of the sagittalfissure; important in emotional processing and rational decision-making.

A taxonomic category subordinate to class; comprises animal families.

A property of many neurons in visual cortex in which they respond to edges presented over a narrow range of orientations.

An inability to fixate visual targets while the head is moving as a result of vestibular damage.

The bones of the middle ear]]


The calcium carbonate crystals that rest on the otolithic membrane overlying the hair cells of the sacculus and utricle.

The gelatinous membrane on which the otoconia lie and in which the tips of the hair bundles are embedded.

Dense calcific structures (literally “ear stones”); important in generating the vestibular signals pertinent to balance.

Portion of photoreceptors made up of membranous disks that contain the photopigment responsible for initiating phototransduction.

Site where the middle ear ossicles transfer vibrational energy to the cochlea.

The peak, positive-going phase of an action potential, caused by high membrane permeability to a cation such as Na+ or Ca2+.

A 9-amino-acid neuropeptide that is both a putative neurotransmitter and a neurohormone.


Encapsulated mechanosensory receptor specialized for the detection of high-frequency vibrations.

System of interconnected brain structures (mainly cingulate gyrus, hippocampus, and hypothalamus) in the medialaspect of the telencephalon and diencephalon described by James Papez. Participates in emotional processing, short-term declarative memory, and autonomic functions.

Term referring to the secretion of hormone-like agents whose effects are mediated locally rather than by the general circulation.

The bifurcated axons of cerebellar granule cells that synapse on dendritic spines of Purkinje cells.

Complete loss of voluntary motor control.

Neurons in the reticular formation of the pons that coordinate the actions of motor neurons in the abducens and oculomotor nuclei to generate horizontal movements of the eyes; also known as the “horizontal gaze center.”]]

parasympathetic nervous system]]

A division of the visceral motor system in which the effectors are cholinergic ganglion cells located near target organs.

Partial loss of voluntary motor control; weakness.

The lobe of the brain that lies between the frontal lobe anteriorly, and the occipital lobe posteriorly.

A neurodegenerative disease of the substantia nigra that results in a characteristic tremor at rest and a general paucity of movement.

Referring to the component of the primary visual pathway specialized for the detection of detail and color; so named because of the relatively small cells involved.

Current flow across neuronal membranes that does not entail the action potential mechanism.

An extraordinarily sensitive voltage clamp method that permits the measurement of ionic currents flowing through individual ion channels.

Region of brainstem gray matter that contains, among others, nuclei associated with the modulation of pain perception.

The potassium-poor fluid that bathes the basal end of the cochlear hair cells.

The connective tissue that surrounds a nerve fascicle in a peripheral nerve.

All nerves and neurons that lie outside the brain and spinal cord.

An influence during development that permits differentiation to occur but does not specifically instruct cell fate.

Transient firing of action potentials in response to a prolonged stimulus; the opposite of tonic.

The visible (or otherwise discernible) characteristics of an animal that arise during development.

The visible body characteristics associated with sexual behaviors.

G-protein-activated enzyme that hydrolizes membrane phospholipids at the inner leaflet of the plasma membrane to release fatty acids such as arachadonic acid.

G-protein-activated enzyme that hydrolizes membrane phospholipids at the inner leaflet of the plasma membrane to release a diacylglycerol and an inositol phosphate such as inositol trisphosphate (IP3).

Vision at high light levels that is mediated entirely by cones.

The evolutionary history of a species or other taxonomic category.

A major division of the plant or animal kingdom that includes classes having a common ancestry.

The innermost of the three layers of the meninges, which is closely applied to the surface of the brain.

Pigmented coat underlying the retina important in the normal turnover of photopigment in rods and cones.

Midline neural structure lying on the dorsal surface of the midbrain; important in the control of circadian rhythms(and, incidentally, considered by Descartes to be the seat of the soul).

A component of the external ear.

Endocrine structure comprising an anterior lobe made up of many different types of hormone-secreting cells, and a posterior lobe that secretes neuropeptides produced by neurons in the hypothalamus.

An inert substance that when administered may, because of the circumstances, have physiological effects.

Region on the superior surface of the temporal lobe posterior to Heschl’s gyrus; notable because it is larger in the left hemisphere in about two-thirds of humans.

Term that refers to structural or functional changes in the nervous system.

Referring to a continually graded organization along one of the major axes of an animal.

Responding to more than one sensory modality.

A state in which neurons or muscle fibers receive synaptic inputs from multiple, rather than single, axons.

One of the three components of the brainstem, lying between the midbrain rostrally and the medulla caudally.

Characteristic encephalographic waves that signal the onset of rapid eye movement sleep.

Collections of neurons in the pons that receive input from the cerebral cortex and send their axons across the midline to the cerebellar cortex via the middle cerebellar peduncle.

A structural feature of membrane ion channels that allows ions to diffuse through the channel.

An extracellular domain of amino acids, found in certain ion channels, that lines the channel pore and allows only certain ions to pass.

The gyrus that lies just posterior to the central sulcus; contains the primary somatic sensory cortex.

Toward the back; sometimes used as a synonym for caudal or dorsal.

Referring to axons that link visceral motor neurons in autonomic ganglia to their targets.

The current produced in a postsynaptic neuron by the binding of neurotransmitter released from a presynapticneuron.

Referring to the component of a synapse specialized for transmitter reception; downstream at a synapse.

The potential change produced in a postsynaptic neuron by the binding of neurotransmitter released from a presynaptic neuron.

An enhancement of synaptic transmission resulting from high-frequency trains of action potentials.

The gyrus that lies just anterior to the central sulcus; contains the primary motor cortex.

Cortical regions in the frontal lobe that are anterior to the primary and association motor cortices; thought to be involved in planning complex cognitive behaviors and in the expression of personality and appropriate social behavior.

Referring to neurons and axons that link visceral motor neurons in spinal cord and brainstem to autonomic ganglia.

Motor association areas in the frontal lobe anterior to primary motor cortex; thought to be involved in planning or programming of voluntary movements.

The first protein translation products synthesized in a cell. These polypeptides are usually much larger than the final, mature peptide, and often contain signal sequences that target the peptide to the lumen of the endoplasmic reticulum.

Referring to the component of a synapse specialized for transmitter release; upstream at a synapse.

A group of nuclei located at the junction of the thalamus and the midbrain; these nuclei are important in the pupillary light reflex, relaying information from the retina to the Edinger-Westphal nucleus.

Sympathetic ganglia that lie anterior to the spinal column (distinct from the sympathetic chain ganglia).

The major cortical target of the neurons in the medial geniculate nucleus.

A major source of descending projections to motor neurons in the the spinal cord and cranial nerve nuclei; located in the precentral gyrus (Brodmann’s area 4) and essential for the voluntary control of movement.

A neuron that directly links muscles, glands, and sense organs to the central nervous system.

Any one of several cortical areas receiving the thalamic input for a particular sensory modality.

see striate cortex.

Pathway from the retina via the lateral genticulate nucleus of the thalamus to the primary visual cortex; carries the information that allows conscious visual perception.

An order of mammals that includes lemurs, tarsiers, marmosets, monkeys, apes, and humans (technically, a member of this order).

A phenomenon in which the memory of an initial exposure is expressed unconsciously by improved performance at a later time.

The thickened anterior end of the primitive streak; an important source of inductive signals during early development.

Axial thickening in the ectoderm of the gastrulas of reptiles, birds, and mammals; the mesoderm forms by the ingression of cells at this site.

Unconscious memories such as motor skills and associations.

Aphasia that derives from cortical damage to those centers concerned with the motor aspects of speech.

DNA sequence (usually within 35 nucleotides upstream of the start site of transcription) to which the RNA polymerase and its associated factors bind to initiate transcription.

Partially processed forms of proteins containing peptide sequences that play a role in the correct folding of the final protein.

Sensory receptors (usually limited to mechanosensory receptors) that sense the internal forces acting on the body; muscle spindles and Golgi tendon organs are the preeminent examples.

The part of the brain that includes the diencephalon and telencephalon (derived from the embryonic forebrainvesicle).

The emotional tone or quality of speech.

The inability to recognize faces; usually associated with lesions to the right inferior temporal cortex.

Molecule consisting of a core protein to which one or more long, linear carbohydrate chains (glycosaminoglycans) are attached.

Closer to a point of reference (the opposite of distal).

Referring to drugs that alter behavior, mood, and perception.

A thalamic nucleus that receives its major input from sensory and association cortices and projects in turn to association cortices, particularly in the parietal lobe.

The perforation in the iris that allows light to enter the eye.

The decrease in the diameter of the pupil that follows stimulation of the retina.

The large principal projection neuron of the cerebellar cortex that has as its defining characteristic an elaborate apical dendrite.

One of the three major nuclei that make up the basal ganglia.

White matter tract that lies on the ventral surface of the medulla and contains axons descending from motor cortexto the spinal cord.

Component of cerebral cortex in the temporal lobe pertinent to olfaction; so named because of its pearlike shape.

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Glial cells that contact both the luminal and pial surfaces of the neural tube, providing a substrate for neuronal migration.

Branch; typically applied to the white and gray communicating rami that carry visceral motor axons to the segmental nerves.

A collection of serotonergic nuclei in the brainstem tegmentum; important in the governance of sleep and waking.

Phase of sleep characterized by low-voltage, high-frequency electroencephalographic activity accompanied by rapid eye movements.

Region of a receptor surface (e.g., the body surface or the retina) that causes a sensory nerve cell (or axon) to respond.

A molecule specialized to bind any one of a large number of chemical signals, preeminently neurotransmitters.

A neuron specialized for the transduction of energy in the environment into electrical signals.

The membrane potential change elicited in receptor neurons during sensory transduction.

Enzyme that converts testosterone to dihydrotestosterone.

A stereotyped (involuntary) motor response elicited by a defined stimulus.

The brief period after the generation of an action potential during which a second action potential is difficult or impossible to elicit.

Change in the anatomical arrangement of neural connections.

An antihypertensive drug that is no longer used due to side effects such as behavioral depression.

The inside-negative electrical potential that is normally recorded across all cell membranes.

Region in the brainstem tegmentum that, when stimulated, causes arousal; involved in modulating sleep and wakefulness.

A network of neurons and axons that occupies the core of the brainstem, giving it a reticulated appearance in myelin-stained material; major functions include control of respiration and heart rate, posture, and state of consciousness.

Laminated neural component of the eye that contains the photoreceptors (rods and cones) and the initial processing machinery for the primary (and other) visual pathways.

A derivative of vitamin A that acts as an inducer during early brain development.

The pathway between ganglion cells in the retina and the optic tectum of vertebrates.

A movement or influence acting from the axon terminal toward the cell body.

The membrane potential of a post-synaptic neuron (or other target cell) at which the action of a given neurotransmitter causes no net current flow.

The photopigment found in rods.

The part of the brain that includes the pons, cerebellum, and medulla (derived from the embryonic hindbrainvesicle).

Segment of the developing rhombencephalon.

The initial, depolarizing, phase of an action potential, caused by the regenerative, voltage-dependent influx of a cation such as Na+ or Ca2+.

Photoreceptors specialized for operating at low light levels.

Anterior, or “headward.

Neurons in the midbrain reticular formation that coordinate the actions of neurons in the oculomotor nuclei to generate vertical movements of the eye; also known as the “vertical gaze center.

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Ballistic, conjugate eye movements that change the point of foveal fixation.

The otolith organ that detects linear accelerations and head tilts in the vertical plane.

Referring to the anterior-posterior plane of an animal.

Mechanism of action potential propagation in myelinated axons; so named because action potentials “jump” from one node of Ranvier to the next due to generation of action potentials only at these sites.

The ganglion containing the bipolar cells that innervate the semicircular canals and otolith organs.

The axons of cells in the CA3 region of hippocampus that form synapses in the CA1 region.

Neuroglial cells in the peripheral nervous system that elaborate myelin (named after the nineteenth-century anatomist and physiologist Theodor Schwann).

The external connective tissue coat of the eyeball.

A defect in the visual field as a result of pathological changes in some component of the primary visual pathway.

Referring to vision in dim light, where the rods are the operative receptors.

Projection neurons in a sensory pathway that lie between the primary receptor neurons and the third-order neurons.

One of a series of more or less similar anterior-posterior units that make up segmental animals.

The anterior-posterior division of animals into roughly similar repeating units.

A family of diffusible, growth-inhibiting molecules (see also collapsin).

The vestibular end organs within the inner ear that sense rotational accelerations of the head.

Increased sensitivity to stimuli in an area surrounding an injury. Also, a generalized aversive response to an otherwise benign stimulus when it is paired with a noxious stimulus.

Diminished sense of hearing due to damage of the inner ear or its related central auditory structures. Contrast with conductive hearing loss.

Pertaining to sensation.

Difficulty in communicating with language that derives from cortical damage to those areas concerned with the comprehension of speech.

see dorsal root ganglia.

Term sometimes used to describe all the components of the central and peripheral nervous system concerned with sensation.

Process by which energy in the environment is converted into electrical signals by sensory receptors.

A biogenic amine neurotransmitter derived from the amino acid tryptophan.

Having two different forms depending on genotypic or phenotypic sex.

Memories that last from seconds to minutes.

A classical method for visualizing neurons and their processes by impregnation with silver salts (the best-known technique is the Golgi stain, developed by the Italian anatomist Camillo Golgi in the late nineteenth century).

The orderly recruitment of motor neurons by size to generate increasing amounts of muscle tension.

Bursts of electroencephalographic activity, at a frequency about 10–14 Hz and lasting a few seconds; spindles characterize the initial descent into non-REM sleep.

Referring to the non-peptide neurotransmitters such as acetylcholine, the amino acids glutamate, aspartate, GABA, and glycine, as well as the biogenic amines.

Slow, tracking movements of the eyes designed to keep a moving object aligned with the fovea.

The cell body.

Referring to the cells of an animal other than its germ cells.

That region of the cerebral cortex concerned with processing sensory information from the body surface, subcutaneous tissues, muscles, and joints; located primarily in the posterior bank of the central sulcus and on the postcentral gyrus.

Components of the nervous system involved in processing sensory information about the mechanical forces active on both the body surface and on deeper structures such as muscles and joints.

Cortical or subcortical arrangements of sensory pathways that reflect the organization of the body.

Segmentally arranged masses of mesoderm that lie alongside the neural tube and give rise to skeletal muscle, vertebrae, and dermis.

A taxonomic category subordinate to genus; members of a species are defined by extensive similarities, including the ability to interbreed.

Term applied to neural connections that entail specific choices between neurons and their targets.

A congenital defect in which the neural tube fails to close at its posterior end.

The portion of the central nervous system that extends from the lower end of the brainstem (the medulla) to the cauda equina.

see dorsal root ganglia.

Sexually dimorphic collection of neurons in the lumbar region of the rodent spinal cord that innervate striated perineal muscles.

The initial flaccid paralysis that accompanies damage to descending motor pathways.

Brainstem tract carrying fibers from the trigeminal nerve to the spinal nucleus of the trigeminal complex (which serves as the relay for painful stimulation of the face).

Region of the cerebellar cortex that receives input from the spinal cord, particularly Clarke’s column in the thoracic spinal cord.

see anterolateral pathway.

Ascending white matter tract carrying information about pain and temperature from the spinal cord to the VP nuclear complex in the thalamus; also referred to as the anterolateral tract.

Individuals who have had the cerebral commissures divided in the midline to control epileptic seizures.

Cases of a disease that apparently occur at random in a population; contrasts with familial or inherited.

Undifferentiated cells from which other cells, including neurons, can be derived.

The actin-rich processes that, along with the kinocilium, form the hair bundle extending from the apical surface of the hair cell; site of mechanotransduction.

The perception of depth that results from the fact that the two eyes view the world from slightly different angles.

Developmental misalignment of the two eyes; may lead to binocular vision being compromised.

Specialized epithelium lining the cochlear duct that maintains the high potassium concentration of the endolymph.

Primary visual cortex in the occipital lobe (also called Brodmann’s area 17). So named because the prominence of layer IV in myelin-stained sections gives this region a striped appearance.

see corpus striatum.

A line found in both the sacculus and utricle that divides the hair cells into two populations with opposing hair bundle polarities.

The cerebrospinal fluid—filled space over the surface of the brain that lies between the arachnoid and the pia.

An 11-amino acid neuropeptide; the first neuropeptide to be characterized.

Nucleus at the base of the midbrain that receives input from a number of cortical and subcortical structures. The dopaminergic cells of the substantia nigra send their output to the caudate/putamen, while the GABAergic cells send their output to the thalamus.

A nucleus in the ventral diencephalon that receives input from the caudate/putamen and participates in the modulation of motor behavior.

The infoldings of the cerebral hemisphere that form the valleys between the gyral ridges.

The addition in space and time of sequential synaptic potentials to generate a larger than normal post-synaptic response.

Laminated structure that forms part of the roof of the midbrain; plays an important role in orienting movements of the head and eyes.

Hypothalamic nucleus lying just above the optic chiasm that receives direct input from the retina; involved in light entrainment of circadian rhythms.

see lateral fissure.

A division of the visceral motor system in vertebrates comprising, for the most part, adrenergic ganglion cells located relatively far from the related end organs.

Specialized apposition between a neuron and its target cell for transmission of information by release and reception of a chemical transmitter agent.

The space that separates pre- and postsynaptic neurons at chemical synapses.

A short-term decrease in synaptic strength resulting from the depletion of synaptic vesicles at active synapses.

A sequence of budding and fusion reactions that occurs within presynaptic terminals to maintain the supply of synaptic vesicles.

Spherical, membrane-bound organelles in presynaptic terminals that store neurotransmitters.

A group of cells in protoplasmic continuity.

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The object of innervation, which can be either non-neuronal targets, such as muscles, glands, and sense organs, or other neurons.

Onion-shaped structures in the mouth and pharynx that contain taste cells.

The fibrous sheet overlying the apical surface of the cochlear hair cells; produces a shearing motion of the stereocilia when the basilar membrane is displaced.

A general term referring to the dorsal region of the brainstem (tectum means “roof”).

A general term that refers to the central gray matter of the brainstem.

The part of the brain derived from the anterior part of the embryonic forebrain vesicle; includes the cerebral hemispheres.

Referring to the region of the visual field of each eye in the direction of the temple.

The hemispheric lobe that lies inferior to the lateral fissure.

A presynaptic (axonal) ending.

A quaternary ammonium compound that selectively blocks voltage-sensitive K+ channels; eliminates the delayed K+ current measured in voltage clamp experiments.

An alkaloid neurotoxin, produced by certain puffer fish, tropical frogs, and salamanders, that selectively blocks voltage-sensitive Na+ channels; eliminates the initial Na+ current measured in voltage clamp experiments.

A collection of nuclei that forms the major component of the diencephalon. Although its functions are many, a primary role of the thalamus is to relay sensory information from lower centers to the cerebral cortex.

Receptors specialized to transduce changes in temperature.

The level of membrane potential at which an action potential is generated.

A specialized junction between epithelial cells that seals them together, preventing most molecules from passing across the cell sheet.

The filamentous structures that link the tips of adjacent stereocilia; thought to mediate the gating of the hair cell’s transduction channels.

Sustained activity in response to an ongoing stimulus; the opposite of phasic.

the topographic mapping of frequency across the surface of a structure, which originates in the cochlea and is preserved in ascending auditory structures, including the auditory cortex.

A general term applied to proteins that regulate transcription, including basal transcription factors that interact with the RNA polymerase to initiate transcription, as well as those that bind elsewhere to stimulate or repress transcription.

Proteins that bind DNA and activate the transcription of DNA.

G-protein involved in the phototransduction cascade.

see sensory transduction.

A class of peptide growth factors that acts as an inducer during early development.

Gender identification with the opposite phenotypic sex.

see neurotransmitter.

Cell membrane molecules that consume energy to move ions up their concentration gradients, thus restoring and/or maintaining normal concentration gradients across cell membranes.

Referring to the presence of three different cone types in the human retina, which generate the initial steps in color vision by differentially absorbing long, medium, and short wavelength light.

A class of antidepressant drugs named for their three-ringed molecular structure; thought to act by blocking the reuptake of biogenic amines.

The sensory ganglion associated with the trigeminal nerve (cranial nerve V).

The receptors for the neurotrophin family of growth factors.

The ability of one tissue or cell to support another; usually applied to long-term interactions between pre- and postsynaptic cells.

A molecule that mediates trophic interactions.

Referring to the long-term interdependence of nerve cells and their targets.

see trophic factor.

An influence of one cell or tissue on the direction of movement (or outgrowth) of another.

Molecules that influence the direction of growth or movement.

Orientation of growth in response to an external stimulus.

Referring to a common physiological test in which the receptive field properties of neurons are gauged against a varying stimulus such that maximum sensitivity or maximum responsiveness can be defined by the peak of the tuning curve.

The eardrum.

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The final, hyperpolarizing phase of an action potential, typically caused by the voltage-dependent efflux of a cation such as K+.

A neuron that gives rise to a descending projection that controls the activity of lower motor neurons in the brainstem and spinal cord.

Signs and symptoms that result from damage to descending motor systems; these include paralysis, spasticity, and a positive Babinski sign.

The otolith organ that senses linear accelerations and head tilts in the horizontal plane.

A 9-amino-acid neuropeptide that acts as a neurotransmitter, as well as a neurohormone.

Referring to the belly; the opposite of dorsal.

The ventral portion of the spinal cord gray matter; contains the primary motor neurons.

Group of thalamic nuclei that receives the somatic sensory projections from the dorsal column nuclei and the trigeminal nuclear complex.

Component of the ventral posterior complex of thalamic nuclei that receives brainstem projections carrying somatic sensory information from the body (excluding the face).

Component of the ventral posterior complex of thalamic nuclei that receives brainstem projections related to somatic sensory information from the face.

The collection of nerve fibers containing motor axons that exit ventrally from the spinal cord and contribute the motor component of each segmental spinal nerve.

The fluid-filled spaces in the vertebrate brain that represent the lumen of the embryonic neural tube.

The sheet of cells closest to the ventricles in the developing neural tube.

Disjunctive movements of the eyes (convergence or divergence) that align the fovea of each eye with targets located at different distances from the observer.

An animal with a backbone (technically, a member of the subphylum Vertebrata).

Literally, a small sac. Used to refer to the organelles that store and release transmitter at nerve endings. Also used to refer to any of the three dilations of the anterior end of the neural tube that give rise to the three major subdivisions of the brain.

The part of the cerebellar cortex that receives direct input from the vestibular nuclei or vestibular nerve.

Involuntary movement of the eyes in response to displacement of the head. This reflex allows retinal images to remain stable while the head is moved.

Referring to the internal organs of the body cavity.

The component of the motor system (also known as the autonomic nervous system) that motivates and governs visceral motor behavior.

Synonymous with autonomic nervous system.

The area in the external world normally seen by one or both eyes (referred to, respectively, as the monocular and visual binocular fields).

A reagent that stains cells when they are alive.

A method that uses electronic feedback to control the membrane potential of a cell, simultaneously measuring transmembrane currents that result from the opening and closing of ion channels.

Term used to describe ion channels whose opening and closing is sensitive to membrane potential.

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The process by which the distal portion of a damaged axon segment degenerates; named after Augustus Waller, a nineteenth-century physician and neuroanatomist.

Difficulty comprehending speech as a result of damage to Wernicke’s language area.

Region of cortex in the superior and posterior region of the left temporal lobe that helps mediate language comprehension. Named after the nineteenth-century neurologist, Carl Wernicke.

A general term that refers to large axon tracts in the brain and spinal cord; the phrase derives from the fact that axonal tracts have a whitish cast when viewed in the freshly cut material.

Memories held briefly in mind that enable a particular task to be accomplished (e.g., efficiently searching a room for a lost object).

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