In this text, the standard Latin forms of anatomical names are anglicized wherever this is possible without loss of euphony. Most anatomical terms have Latin origins, and most names related to diseases are derived from Greek words. Many words are defined and explained (without etymology) in the text. If you cannot find a word in this glossary, try the Index. For eponyms (names of people, applied to structures, syndromes, or diseases) consult the CD-ROM that accompanies the printed book.
Eng., English; Fr., French; Ger., German; Gr., Greek; L., Latin; O.E., Old English
Gr. a, without + boule, will. A loss of willpower. (Also spelled aboulia.)
Gr. aden, gland + hypophysis (which see). The part of the pituitary gland derived from the pharyngeal endoderm (Rathke's pouch). Its largest part is the anterior lobe of the pituitary gland.
a, neg. + Gr. diadochos, succeeding + kinesis, movement. Inability to perform rapidly alternating movements. Also called dysdiadochokinesia.
Gr. a, without + geuein, to taste. Loss of the sense of taste.
a, neg. + Gr. gnosis, knowledge. Lack of ability to recognize the significance of sensory stimuli (auditory, visual, tactile, etc., agnosia).
a, neg. + Gr. graphein, to write. Inability to express thoughts in writing owing to a central lesion.
a, neg. + Gr. kinesis, movement. Loss of movement (adjective, akinetic). Often used to mean severe bradykinesia, a feature of advanced Parkinson's disease.
a, neg. + Gr. lexis, word. Loss of the power to grasp the meaning of written or printed words and sentences.
Gr. allos, other + L. cortex, bark. Phylogenetically older cerebral cortex, usually consisting of three layers. Includes paleocortex and archicortex.
Gr. allos, other + dynamis, power or force. A condition in which the nervous system misinterprets a sensory stimulus. The word is usually used when a harmless sensation such as touch is consciously felt as pain, which may be excruciating.
a, neg. + Gr. makros, long + inos, fiber. Amacrine nerve cell of the retina.
Hippocampus, which has an outline in cross section suggestive of a ram's horn. Also known as the cornu Ammonis. Ammon was an Egyptian deity with a ram's head.
Gr. amoibe, change. Relating to a cell that continuously changes its shape and looks like an amoeba.
Gr. aneurysma, dilation or widening. An abnormal widening of an artery. It can compress nearby structures and may burst.
Ger. arrangement, layout (among other meanings). The grouping of cells in an embryo that is the beginning of an anatomical structure (Plural:anlagen).
(also Anopsia). an, neg. + Gr. opsis, vision. Defect of vision.
Gr. anti, against + dromos, racecourse. Of impulses traveling in the opposite direction to what is usual in an axon.
a, neg. + Gr. phasis, speech. Defect of the power of expression by speech or of comprehending spoken or written language.
a, neg. + Gr. prassein, to do. Inability to carry out purposeful movements in the absence of paralysis.
Gr. arachne, spider's web + eidos, resemblance. Meningeal layer that forms the outer boundary of the subarachnoid space.
Gr. arche, beginning + diminutive of cerebrum. Phylogenetically old part of the cerebellum, functioning in the maintenance of equilibrium. Also spelled archeocerebellum.
Gr. arche, beginning + L. cortex, bark. Threelayered cortex included in the limbic system; located mainly in the hippocampus and dentate gyrus of the temporal lobe. Also spelled archeocortex.
Area in the caudal part of the floor of the fourth ventricle.
a, neg. + stereos, solid + gnosis, knowledge. Loss of ability to recognize objects or to appreciate their form by touching or feeling them.
Gr. astron, star + kytos, hollow (cell). Type of neuroglial cell.
a, neg. + Gr. syn, with + ergon, work. Disturbance of the proper association in the contraction of muscles that ensures that the different components of an act follow in proper sequence, at the proper moment, and of the proper degree, so that the act is executed accurately.
a, neg. + Gr. taxis, order. Loss of power of muscle coordination, with irregularity of muscle action.
Gr. athere, porridge. Thickening of the lining of an artery caused by deposition of lipid material.
Gr. athetos, without position or place. Affliction of the nervous system caused by degenerative changes in the corpus striatum and cerebral cortex and characterized by bizarre, writhing movements of the fingers and toes, especially.
Gr. atlao, I sustain. The first cervical vertebra.
a, neg. + Gr. tresis, perforation. Absence of a passage caused by an error in development.
a, neg. + Gr. trophe, nourishment. Diminution of size and functional activity; wasting; emaciation.
Gr. auto, self + im, not + munis, serving. A condition in which antibodies or cells of the immune system attack a part of their own body.
Gr. autos, self + nomos, law. Autonomic system; the efferent or motor innervation of viscera.
Gr. autos, self + L. radius, ray + Gr. graphein, to write. Technique that uses a photographic emulsion to detect the location of radioactive isotopes in tissue sections. Also called radioautography.
Gr. axon, axis + lemma, husk. Plasma membrane of an axon.
Gr. axon, axis. Efferent process of a neuron that conducts impulses to other neurons or to muscle fibers (striated and smooth) and gland cells.
Region of the nerve cell body from which the axon arises; it contains no Nissl material.
Changes in the cell body of a neuron after damage to its axon.
Gr. axon, axis + plasm, anything formed or molded. Cytoplasm of the axon.
Gr. baros, weight + receptor, receiver. Sensory nerve terminal that is stimulated by changes in pressure, as in the carotid sinus and aortic arch.
Ventral part of the cerebral peduncle of the midbrain on each side, separated from the dorsal part by the substantia nigra. Also called the crus cerebri.
Gr. brady, slow + kinesis, movement. Abnormal slowness of movements; one of the three major abnormalities resulting from Parkinson's disease.
In the mature human brain, denotes the medulla, pons, and midbrain. In descriptions of the embryonic brain, the diencephalon is included as well.
Referred at one time to the medulla oblongata, but in the context of “corticobulbar tract,” refers to the brain stem, in which motor nuclei of cranial nerves are located.
Part of the corpus striatum, so named because it has a long extension or tail.
A protein molecule in a cell membrane that allows the passage of a particular ion, such as sodium, calcium, potassium or chloride, into or out of the cell, following
a concentration gradient. Channels typically are gated, meaning that they open and close in response to neurotransmitters or local changes in membrane potential.
Using acetylcholine as a neurotransmitter.
Gr. chorde, cord + tome, a cutting. Division of the spinothalamic and spinoreticular tracts for intractable pain (tractotomy). Also spelled cordotomy.
Gr. chorion, a delicate membrane + eidos, form. Choroid or vascular coat of the eye; choroid plexuses in the ventricles of the brain. Also spelled chorioid.
Gr. chroma, color + lysis, dissolution. Dispersal of the Nissl material of neurons after axon section or in viral infections of the nervous system.
Small regions composed of atypical brain tissue in the walls of the third (see Ch. 11) and fourth (see Ch. 9) ventricles. These structures lack a blood-brain barrier and have chemoreceptor or neurosecretory functions.
Gr. kline, bed + oides, shape. The anterior and posterior clinoid processes are four bony points at the corners of the diaphragma sellae (q.v.), named from a fancied resemblance to a four-poster bed.
Persistent shortening, as in a muscle paralyzed for a long time.
Gr. korone or L. corona, a crown. The coronal suture traverses the top of the head, separating the frontal bone from the parietal bones. A coronal section is one cut in or parallel to the plane of the coronal suture; these planes are sometimes called frontal.
Gr. kytos, a hollow vessel + solution. Soluble portion of the cytoplasm, excluding all membranous and particulate components.
Gr. dendrites, related to a tree. Process of a nerve cell on which axons of other neurons terminate. Sometimes also used for the peripheral process of a primary sensory neuron, although this has the histological and physiological properties of an axon.
Loss of innervation due to transection of axons or death of the somata of the innervating neurons.
Gr. diabetes, a syphon. Disease with excessive production of urine. In diabetes mellitus (L. mellitus, sweet), the urine contains sugar, whereas in diabetes insipidus (L. in, not + sapor, flavor), the urine is watery and quite tasteless.
Gr. dia, across + phragma, wall + L. sellae, of a saddle. The membrane of dura mater that covers the sella turcica and is pierced by the pituitary stalk.
Gr. dia, through + enkephalos, brain. Part of the cerebrum, consisting of the thalamus, epithalamus, subthalamus, and hypothalamus; the more caudal and medial part of the prosencephalon of the developing embryo.
Gr. diploos, double + ops, eye. Double vision.
From dorsal and flexor. Movement at the ankle that raises the toes and depresses the heel.
Gr. dys, difficult or disordered + kinesis, movement. Abnormality of motor function characterized by involuntary, purposeless movements.
Gr. dys, difficult or disordered + metron, measure. Disturbance of the power to control the range of movement in muscle action.
Gr. ektos, outside + derma, skin. Most dorsal layer of cells of the early embryo, which gives rise to the epidermis, neural tube, neural crest, etc.
Gr. oidema, swelling. Abnormal accumulation of fluid in a tissue.
Gr. embolos, plug + L. forma, form. Emboliform nucleus of the cerebellum.
Gr. embolos, plug. Fragment of a thrombus that breaks loose and eventually obstructs an artery.
Gr. endo, within + myos (mys), muscle. The delicate connective tissue that surrounds and separates individual contractile fibers of a muscle.
Gr. endon, within + neuron, nerve. Delicate connective tissue sheath surrounding an individual nerve fiber of a peripheral nerve. Also called the sheath of Henle.
Gr. endo, within + a molded form (cytoplasm) + L. reticulum, small net. An array of membranes within a cell. Rough endoplasmic reticulum is associated with ribosomes, where protein molecules are assembled.
Gr. en, in + gramma, mark. Used in psychology to mean the lasting trace left in the brain by previous experience; a latent memory picture.
Gr. entos, within + rhis (rhin-), nose. The entorhinal area is the anterior part of the parahippocampal gyrus of the temporal lobe adjacent to the uncus. It is included in the lateral olfactory area.
Gr. eos, dawn + in (suffix that denotes an organic compound that is not a base) + Y (for yellowish, in contrast to eosin B which has a bluish cast). A red anionic dye of the xanthene series, used as a microscopical stain. It colors cytoplasm and connective tissue components various shades of orange, pink, and red.
Gr. ependyma, an upper garment. Lining epithelium of the ventricles of the brain and central canal of the spinal cord.
Gr. epi, upon + neuron, nerve. Connective tissue sheath surrounding a peripheral nerve.
Gr. epi, upon + thalamos, inner chamber. Region of the diencephalon above the thalamus; includes the pineal gland.
Gr. epi, upon + thele, nipple. A layer (or multiple layers) of cells covering any external or internal surface. Originally (1700) this word meant thin skin covering the nipples or lips; later, it was applied to all skin. By the 1870s, the term was being used in its present sense.
Gr. ethmos, sieve + oides, shape. A bone of the skull that forms the medial part of the floor of the anterior cranial fossa and the upper part of the skeleton of the nasal cavities. The bone includes the cribriform plate.
Gr. eu, well + phone, sound. Agreeable sound or easy pronunciation.
Vague and confusing term applied to motor parts of the central nervous system other than the pyramidal motor system.
In an arteriovenous fistula, blood is shunted directly from an artery into a vein or venous sinus.
(plural, foramina). L. forare, to pierce. A hole.
Describes a neuron that uses gamma-aminobutyrate (GABA) as its principal synaptic transmitter.
Gr. knot or subcutaneous tumor. Swelling composed of nerve cells, as in cerebrospinal and sympathetic ganglia. Also used inappropriately for certain regions of gray matter in the brain (e.g., basal ganglia of the cerebral hemisphere).
Gr. gaster, belly + kneme, leg. The muscle largely responsible for the bulging contour of the calf of the human leg.
Gr. glue. Neuroglia, the interstitial or accessory cells of the central nervous system.
Gr. glia, glue + blastos, germ. Embryonic neuroglial cell.
Gr. glia, glue + soma, body. Granules seen by light microscopy in neuroglial cells, especially astrocytes. They are probably mitochondria.
Diminutive of L. glomus, ball of yarn. Synaptic glomeruli of the olfactory bulb and cerebellum.
Gr. glycyx, sweet + kalyx, cup. Outer coating of carbohydrate molecules on the surface of cells.
An array of membranous compartments within the cytoplasm, where proteins combine with carbohydrates to form glycoproteins.
(also gonadotropic). Gr. gone, generation + trephein, to feed (trophe, food), or trepein, to turn (tropos, a turning). Gonadotrophic hormones are secreted by the anterior lobe of the pituitary gland and in pregnancy by the placenta. They act upon the gonads (ovary or testis) and are essential for the functions of these organs.
Ger. haar, hair + scheibe, disk. Small elevated area of skin that develops in association with specialized hair follicles and serves as a receptor for tactile stimuli.
Gr. helix, snail or coil + trema, hole. The communication between the scala tympani and scala vestibuli at the apex of the cochlea.
From Eng. hematein + alum. A solution containing hematein and aluminum ions, used to stain the nuclei of cells blue. (Hematein is a yellow dye made by oxidation of hematoxylin, which is a colorless compound extracted from the wood of the logwood tree, Hematoxylon campechianum.)Hemalum is frequently used with eosin Y, a dye that colors tissue components other than nuclei pink. The combination (“H & E”) is the most frequently used staining method in pathology laboratories.
Gr. hemi, half + an, neg. + opsis, vision. Loss of half of a field of vision. Also called hemianopsia.
Gr. hemi, half + ballismos, jumping. Violent form of motor restlessness that involves one side of the body, caused by a destructive lesion involving the subthalamic nucleus.
Gr. hemi, half + plege, a blow or stroke. Paralysis of one side of the body.
Gr. herpein, to creep + zoster, waist-belt. Virus infection of neurons in a sensory ganglion, causing painful inflammation with small blisters in the corresponding area of skin. (Also called shingles; systemic invection with the same virus causes chicken pox.)
Gr. hippos, horse + kampos, sea monster; also the zoological name for a genus of small fishes known as sea horses. Rather inappropriate name given to a gyrus that constitutes an important part of the limbic system; produces an elevation on the floor of the temporal horn of the lateral ventricle.
Gr. homois, like + stasis, standing. Tendency toward stability in the internal environment of the organism.
Gr. homonymos and L. homonymus, having the same name. Applied to defects in the same part (left or right) of the visual field of both eyes, in consequence of transection of the visual pathway posterior to the optic chiasma.
Gr. hormaein, to stir up. A compound secreted into the blood, which exercises a specific physiological function elsewhere in the body.
Gr. hydror, water + kephale, head. Excessive accumulation of cerebrospinal fluid.
Gr. hyper, over + acacias, a hearing. Abnormal loudness of perceived sounds.
Gr. hyper, above measure + L. tension, I stretch. (Before 1700, the word tension was incorrectly used as a synonym for pressure.) Abnormally high arterial blood pressure.
Gr. from hypo, under + phytin, to grow. The pituitary gland (considered as an attachment underneath the brain).
Gr. hypo, under + thalamus, inner chamber. Region of the diencephalon that serves as the main controlling center of the autonomic nervous system.
The normal condition in which axons and their presynaptic endings make functional contact with other cells. The associated verb is innervate.
Gr. ischein, to check + haimos, blood. Condition of tissue that is not adequately perfused with oxygenated blood.
Gr. ischion, hip joint + L. caverna, cave or hollow. Paired muscle associated with the bodies of erectile tissue on either side of the base of the penis.
Gr. isos, equal + L. cortex, bark. Cerebral cortex having six layers (neocortex).
Gr. kinesis, movement + aisthesis, sensation. Sense of perception of movement.
Gr. konis, dust + L. cortex, bark. Areas of cerebral cortex that contain large numbers of small neurons; typical of sensory areas.
Gr labyrinthos, building with intricate passages. The cavities and canals of the inner ear within the petrous part of the temporal bone.
Diminutive of L. lamina, plate or leaf. A thin layer or membrane.
Gr. lemniskos, fillet (a ribbon or band). Used to designate a bundle of nerve fibers in the central nervous system (e.g., medial lemniscus and lateral lemniscus).
Gr. leptos, slender + meninx, membrane. Arachnoid and pia mater.
Gr. makros, large + glia, glue. Larger types of neuroglial cells: astrocytes, oligodendrocytes, and ependymal cells.
Gr. makros, great + phagein, to eat. A type of white blood cell (monocyte) that has entered connective tissue and assumed phagocytic properties.
Gr. makros, large + osme, smell. Having the sense of smell strongly or acutely developed.
Bridge of gray matter that connects the thalami of the two sides across the third ventricle; present in 70% of human brains. Also called the interthalamic adhesion.
Gr. mastos, breast + oeides, shape. The mastoid process is the downwardly projecting part of the temporal bone behind the ear.
Malignant tumor of young children, usually in the midline of the cerebellum, enlarging into the fourth ventricle and spreading by way of the subarachnoid space to other parts of the central nervous system.
Gr. mesos, middle + enkephalos, brain. The midbrain; also its embryonic precursor, the part of the neural tube interposed between the forebrain and hindbrain.
Gr. mesos, middle + derma, skin. Middle layer of cells of the early embryo, which gives rise to connective tissues, muscle, etc.
Gr. meta, after + thalamus, inner chamber. Medial and lateral geniculate bodies (nuclei).
Gr. meta, after + enkephalos, brain. Pons and cerebellum; the more rostral of the two divisions of the rhombencephalon or hindbrain.
Gr. mikros, small + glia, glue. Type of neuroglial cell.
Gr. mikros, small + osme, smell. Having a sense of smell, but of relatively poor development.
Gr. mikros, small + L. villus, hair. Hair-like projections of a cell, typically presenting a striated appearance in light microscopy but individually resolved by the electron microscope and seen to be cytoplasmic protrusions.
Gr. mimetikos, imitative. Muscles of expression supplied by the facial nerve; sometimes referred to as mimetic muscles.
Gr. meiosis, diminution. A drug causing constriction of the pupil of the eye.
Gr. mitos, thread + chondros, granule. A cytoplasmic organelle with distinctive ultrastructure, containing respiratory enzymes.
Gr. mneme, memory. Pertaining to memory.
or mucous membrane. From L. mucus. The moist lining of a cavity or hollow organ, consisting of an epithelium with glands that secrete mucus, the underlying lamina propria, and (in the alimentary tract) the muscularis mucosae.
Gr. myos, muscle + a, without + sthenos, strength + L. gravis, heavy (severe). Disease in which there is failure of neuromuscular transmission (see Ch. 3).
Gr. myelos, marrow + enkephalos, brain. Medulla oblongata; the more caudal of the two divisions of the rhombencephalon or hindbrain.
Gr. myelos, marrow. Layers of lipid and protein substances that form a sheath around axons.
Gr. myos, muscle + enteron, intestine. The myenteric plexus lies between the longitudinal (outer) and circular layers of smooth muscle of the intestine and other parts of the alimentary tract.
Gr. mydriasis, enlargement of the pupil. A drug causing dilation of the pupil of the eye.
Gr. myos, muscle + epi, upon + thele, nipple. Contractile cell that embraces a secretory unit (acinus or alveolus) of a gland and propels the contents into a duct.
Gr. myos, muscle + trephein, to nourish. Responsible for maintaining the structural and functional integrity of muscle (principally by chemical agents from motor neurons, hence the earlier but ambiguous term “neurotrophic”).
Gr. neos, new + diminutive of cerebrum. Phylogenetically newest part of the cerebellum present in mammals and especially well developed in humans. Ensures smooth muscle action in the finer voluntary movements.
Gr. neos, new + L. cortex, bark. Six-layered cortex, characteristic of mammals and constituting most of the cerebral cortex in humans.
Gr. neos, new + L. striatus, striped or grooved. Phylogenetically newer part of the corpus striatum that consists of the caudate nucleus and putamen; the striatum.
Gr. neuron, nerve + algein, to suffer. Pain attributed to abnormal stimulation of sensory fibers in the peripheral nervous system.
Gr. neurites, of a nerve. Cytoplasmic processes of neurons. The term embraces both axons and dendrites.
Gr. neuron, nerve + bios, life + taxis, arrangement. Tendency of nerve cells to move during
embryological development toward the area from which they receive the most stimuli.
Gr. neuron, a nerve + blastos, germ. Embryonic nerve cell.
Gr. neuron, nerve + L. fibrilla, diminutive of fibra, fiber. Filaments in the cytoplasm of neurons (see Ch. 2).
Gr. neuron, nerve + glia, glue. Accessory or interstitial cells of the nervous system; includes astrocytes, oligodendrocytes, microglial cells, ependymal cells, satellite cells, and Schwann cells.
Gr. neuron, nerve + hypophysis. An endocrine organ that is a ventral protuberance of the hypothalamus, comprising the median eminence of the tuber cinereum, the infundibular stem (which is the nervous tissue of the pituitary stalk) and the neural lobe or infundibular process, which is the major part of the posterior lobe of the pituitary gland.
Gr. neuron, nerve + keras (kerat-), horn. Fibrillar material consisting of proteins that remain after lipids have been dissolved from myelin sheaths.
Gr. neuron, nerve + lemma, husk. Delicate sheath surrounding a peripheral nerve fiber consisting of a series of neurolemma cells or Schwann cells. Also spelled neurilemma.
Gr. neuron, nerve + -oma, indicating a tumor. Swelling of a severed or otherwise injured nerve, containing a profusion of axonal sprouts that have failed to regrow usefully.
Gr. a nerve. Morphological unit of the nervous system consisting of the nerve cell body and its processes (dendrites and axon).
Gr. neuron, nerve + pilos, felt. Complex net of nerve cell processes that occupies the intervals between cell bodies in gray matter.
The activity of a cell that has the signaling properties of a neuron and the secretory properties of an endocrine cell: a neuron that releases a hormone into the blood.
Diminutive of nucleus (see below). An inclusion within the nucleus of a cell, composed of protein and RNA.
Gr. nystagmos, a nodding, from nystazein, to be sleepy. Involuntary oscillation of the eyes.
Gr. oligos, few + dendron, tree + kytos, hollow (cell). Type of neuroglial cell. Forms the myelin sheath in the central nervous system in the same manner as the Schwann cell in peripheral nerves.
Gr. ontos, being + genesis, generation. Development of an individual. The adjective ontogenetic, which means much the same as “embryological” or “developmental,” is used in contrast to “phylogenetic” (which see).
Gr. otos, of the ear. The otic vesicle is the anlage of the inner ear. The otic ganglion is near the middle ear.
Gr. otos, of the ear + lithos, stone. One of the particles of calcium carbonate associated with the hair cells of the utricle and saccule (otolithic organs) of the inner ear.
Gr. oxys, sharp + tokos, birth. An octapeptide hormone of the neurohypophysis that stimulates the smooth muscle of the uterus and the myoepithelial cells of the mammary glands.
Gr. pachys, thick + meninx, membrane. Dura mater.
Gr. palaios, old + diminutive of cerebrum. Phylogenetically old part of the cerebellum that functions in postural changes and locomotion.
Gr. palaios, old + L. cortex, bark. Olfactory cortex consisting of three to five layers.
Gr. palaios, old + L. striatum, striped or grooved. Phylogenetically older and efferent part of the corpus striatum; the globus pallidus or pallidum.
Pallidum (see below) + L. fugere, to flee from. Describes the axons of neurons in the globus pallidus that conduct impulses to other parts of the brain.
Gr. paralysis, secret undoing; from para, beside + lyein, to loosen. Loss of the power of motion.
Gr. para, beside or beyond + plege, a stroke or blow. Paralysis of both legs and lower part of trunk.
Gr. para, beside + L. medianus, in the middle. In a plane parallel to the median or midsagittal plane.
Gr. para, beside + L. sagitta, arrow. A word sometimes used instead of sagittal for a sagittal plane or section that is parallel to but not in the midline.
Gr. parenchein, to pour in beside. Essential and distinctive tissue of an organ. (The name is from an early notion that internal organs contained material poured in by their blood vessels.)
Gr. parienai, to relax. Partial paralysis.
Diminutive of L. patina, a pan. The kneecap bone embedded in the tendon of the quadriceps group of muscles, which are extensors of the knee joint.
Eng. Route within the central nervous system consisting of interconnected populations of neurons that serve a common function. A pathway often contains one or more tracts.
Gr. peri, around + karyon, nut, kernel. Cytoplasm surrounding the nucleus. Sometimes refers to the cell body of a neuron.
Gr. perinaion. Region consisting of the genitalia, the anus, and the immediately surrounding and intervening region.
Gr. peri, around + neuron, nerve. Cellular and connective tissue sheath surrounding a bundle of nerve fibers in a peripheral nerve.
Gr. phagein, to eat + kytos, vessel (cell). A cell that can engulf and internalize smaller objects such as bacteria and fragments of dead cells.
Gr. phalanx, a formation of soldiers. Phalangeal cells are in lines alongside the sensory cells of the organ of Corti.
Gr. phylon, race + genesis, origin. Evolutionary history, typically as deduced from comparative anatomy.
From L. planta, plant; also applied to the foot. An adjective that relates to the sole of the foot (which often treads on small plants). Theplantaris muscle is a small calf muscle that pulls on the sole of the foot. It is very small in the human leg but larger in the legs of quadrupeds.
is bending the ankle so that the toes point downward.
Gr. pneuma, air + enkephalos, brain + graphe, a writing. Replacement of cerebrospinal fluid by air followed by x-ray examination (pneumoencephalogram); permits visualization of the ventricles and subarachnoid space. This technique has been replaced by computed tomography (CT scan).
(From positive electron.) Subatomic particle with the same mass as an electron and equal but opposite charge. Positrons emitted by radioactive elements combine with electrons, with elimination of matter and emission of x-rays. Detection of the latter forms the basis of positron emission tomography (PET).
L post, after + parturire, to bring forth. Describes the condition of a mother who has recently given birth.
Steroid hormone secreted by the corpus luteum and the placenta.
Gr. pros, before + enkephalos, brain. Forebrain, consisting of the telencephalon (cerebral hemispheres) and diencephalon (thalamus and nearby structures).
Gr. prosopon, person or face + agnosia (q.v.). Inability to recognize previously familiar faces.
Gr. psalterion, an ancient stringed instrument like a zither. The name is sometimes given to the posterior part of the body of the fornix, including the hippocampal commissure.
Gr. ptosis, a falling. Drooping of the upper eyelid.
A molecular channel in a cell membrane associated with enzymes that enable it to move ions in or out of the cell against a concentration gradient, with expenditure of energy.
Corticospinal and corticobulbar tracts. So-called because the corticospinal tracts occupy the fancifully pyramid-shaped area on the ventral surface of the medulla. The term pyramidal tract refers specifically to the corticospinal tract.
Gr. seam. Anatomical structure in the midline. In the brain, several raphe nuclei are in the midline of the medulla, pons, and midbrain. Their names are partly Latinized, as in nucleus raphes magnus (great nucleus of the raphe), etc.
Gr. rhis, nose, therefore related to the nose. Rhinal sulcus in the temporal lobe indicates the margin of the lateral olfactory area.
Gr. rhis (rhin-), nose + enkephalos, brain. Obsolete term that referred to components of the olfactory system. In comparative neurology, structures incorporated in the limbic system (especially the hippocampus and dentate gyrus) were included.
Gr. rhombos, a lozenge-shaped figure + enkephalos, brain. Pons and cerebellum (metencephalon) and medulla (myelencephalon).
After Wilhelm Konrad Roentgen (1845-1923), who discovered x-rays, + Gr. gramma, a letter or record. Picture made with x-rays; more often called an x-ray or a radiograph.
Adjective from L. rostrum, beak, snout. Along the axis of the central nervous system, toward the nose. In human anatomy, approximately equivalent in the brain stem and spinal cord to “superior” and in the forebrain to “anterior.” Opposite of caudal.
Fr. saccader, to jerk. Saccadic or quick movements of the eyes in altering direction of gaze.
Gr. skotos, darkness. A blind area in the field of vision, due to damage in the retina or central nervous system.
Area ventral to the genu and rostrum of the corpus callosum on the medial aspect of the frontal lobe that is the site of the septal nuclei.
From L. solea, sole of a foot or sandal, or the flat fish called sole in English. A muscle in the calf of the leg, deep to the gastrocnemius. Its action presses the sole onto the ground.
Gr. somatikos, bodily. Denoting the body, exclusive of the viscera (as in somatic efferent neurons that supply the skeletal musculature).
Having to do with somatic sensation. Synonymous with somesthetic.
Gr. soma, body + topos, place. Representation of parts of the body in corresponding parts of the brain.
Gr. soma, body + aisthesis, perception. Consciousness of having a body. Somesthetic senses are those of pain, temperature, touch, pressure, position, movement, and vibration. Also spelled somaesthetic.
Gr. sphen, wedge + oeides, shape. A bone of complex form that extends across the base of the skull. It is interposed (“wedged”) between the cranial vault and the bones of the facial skeleton.
Gr. splenion, bandage. Thickened posterior extremity of the corpus callosum.
From Middle English asquint, with the eyes askew. See also strabismus.
Gr. stenos, narrow. Abnormal narrowing of a tube or passage.
Gr. stereos, solid + taxis, arrangement. Relating to a surgical procedure for introducing the tip of an electrode or other instrument into a predetermined position within the brain. The position is calculated from three-dimensional coordinates based on bony landmarks and supplemented by images obtained by CT or MRI.
Gr. strabismos, a squinting. Constant lack of parallelism of the visual axes of the eyes. Also known as a squint. (This is the only correct usage of the word squint.)
Column of small neurons at the apex of the dorsal gray horn throughout the spinal cord.
Gr. synapsis, junction. Word introduced by Sherrington in 1897 for the site at which one neuron is excited or inhibited by another neuron.
Gr. syndrome, the act of running together or combining. Collection of concurring clinical symptoms and signs. A syndrome usually is due to a single cause. The word is often used incorrectly as a synonym for “disease.”
Gr. syrinx, pipe, tube + myelos, marrow. Condition characterized by central cavitation of the spinal cord and gliosis around the cavity.
Gr. tanyo, stretch + kytos, hollow (cell). Specialized type of elongated ependymal cell present in the floor of the third ventricle.
Gr. telos, end + enkephalos, brain. Cerebral hemispheres; the more lateral and rostral of the two divisions of the prosencephalon or forebrain.
Gr. telos, end + dendrion, tree. Terminal branches of axons.
Gr. tetra-, four + plege, a blow or stroke. Paralysis that affects the four limbs. Also called quadriplegia.
Gr. thalamus, an inner chamber; also meant a bridal couch, so that the pulvinar (q.v.) was its cushion or pillow. Galen made up the word thalamus, and Willis was probably the first to use the word in its modern sense.
O.E. therscwald, a house's door sill or point of entry. In physiology, the point at which a stimulus brings about a response.
Gr. thrombos, clot. Clotted blood in a living blood vessel. Thrombosis occurs at sites of irregularity, typically due to atheroma in arteries.
Gr. tomos, cutting + graphein, to write. Production of images of sections through a part of the body. Computed tomography with x-rays and nuclear magnetic resonance imaging are valuable diagnostic techniques.
, tonus. Gr. tonos, pitch (sound), or tension. The normal state of firmness and elasticity of muscles caused by partial contraction of some of their fibers.
Gr. tonos, or tension + L. fibra, thread. An intracellular filament that contributes to maintaining the shape and position of a cell.
Diminutive of L. traba or Gr. trapes, a wooden beam. A component of a net-like arrangement of fibrous, muscular or bony structures, such as the connective tissue filaments that bridge the subarachnoid space, or the spicules and lamellae of cancellous bone.
Transverse fibers of the auditory pathway situated at the junction of the dorsal and ventral portions of the pons.
Gr. trephein, to feed; trophe, food or nourishment; trophos, a feeder. Relating to nutrition. The term is extended to chemically mediated beneficial interactions among cells and organs. Frequently part of a word, as in thyrotrophic hormone, which stimulates the thyroid gland.
Gr. tropos, a turning. An influence that changes or controls the direction in which a molecule, a cell or an organ moves. Usually encountered as the suffix -tropic or -tropism. Tropisms are important in the embryonic development of the nervous system. As a suffix, -tropic is sometimes interchangeable with -trophic (q.v.). For example, the name thyrotropic hormone signifies that this pituitary hormone passes from the blood into the thyroid gland. The name thyrotrophic hormone indicates its action on the gland.