T
1-10 A B C D E F G H I J K L M N O P Q R S T U V W XYZT-cell
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T-cells or T-lymphocytes play an important role in human immunity. They are formed in the thymus gland and react highly specifically against the particular type of antigen that initiated their development. T-cells are capable of regulating other kinds of immune cells (called helper T-cells) or capable of destroying infected or neoplastic cells (called cytotoxic T-cells).
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T-helper cells are the most numerous of the T-cells. They "help" in the functions of the immune system in many ways including increasing the effectiveness of other types of immune cells.
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T-cells, or T-lymphocytes, play an important role in human immunity. They are formed in the thymus gland and react highly specifically against the particular type of antigen (foreign, potentially dangerous substance in the body) that initiated their development.
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The T-suppressor cells are believed to regulate the activities of the other types of T-cells, keeping them from causing excessive immune reactions that might be severely damaging to the body.
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T-suppressor cells are a type of white blood cell that specifically suppress immune responses. They can act on either T-cells or B-cells and play a continuous role in immunological regulation.
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A t-test is a statistical method analogous to determine whether there are differences between two means or between a target value and the calculated mean; the formula for the t-test is the standard deviation for sample sizes of less than 30 cases divided by the deviation from the mean.
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T12 is the twelfth thoracic vertebra.
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T3 is the symbol for 3,5,3'-triiodothyronine, a thyroid hormone. It is present in blood and in thyroid gland.
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T4 is the symbol for thyroxine, the hormone produced by the thyroid.
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Tachycardia is the rapid beating of the heart, usually applied to rates over 100 beats per minute.
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Tactile refers to the sense of touch.
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The talus is the largest of the seven bones that comprise the ankle.
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Tangent means touching at a single point. In geometry, tangent means specifically meeting a curve or surface at a point and having at that point the same direction as the curve or surface. For example, a line may be tangent to a curve, a curve tangent to a surface, and two surfaces tangent to each other. A tangent plane is a plane that touches a surface in a point or line.
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A target is a display placed in front of a test subject during a neurosensory experiment. This target usually has several LEDs (small lights called light emitting diodes) spread over the display. When one of the LEDs lights up, the test subject has to point to it with a laser beam. The laser itself is fixed on the forehead or on top of the head of the test person, so he/she has to move the head to point to the target. These types of experiments are used to determine reaction time and coordination.
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Taurine is a crystallizable substance formed by the decomposition of taurocholic acid, which occurs as a constituent of bile.
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Teflon is a man-made plastic from tetrafloroethylene. It can range in use from an impervious coating to a fabric.
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Telemetered refers to telemetry - the science and technology of automatic transmission and acquisition of data from remote locations.
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Telemetry is the science and technology of automatic transmission and acquisition of data from remote locations.
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A tendon is a thick strand or sheet of tissue that attaches a muscle to a bone. Tendons consist of collagen fibers and are therefore inelastic: they transfer the force exerted by muscular contraction, acting to move parts of the body.
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Tension is the act of stretching or the condition of being stretched, or a force tending to produce elongation or extension.
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Terrestrial means originating from the Earth.
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Testosterone is a principal male sex hormone. Though this hormone normally (and necessarily) occurs in small amounts in females, it is chiefly known as the hormone responsible for stimulating the development of male sex organs and male secondary sexual characteristics, e.g. facial hair, deepening of the voice, and muscle development.
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Tetanus is an acute, often fatal infectious disease caused by a bacillus, Clostridium tetani, that generally enters the body through wounds, characterized by rigidity and spasmodic contraction of the voluntary muscles.
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Therapeutic means having healing or curative powers.
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A thermistor is a device for determining temperature.
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A thermoluminescent dosimeter is a small device used to measure radiation, which is done by measuring the amount of visible light emitted from a crystal in a detector when exposed to ionizing radiation.
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Thermophilus pertains to a thermophile, which is an organism that grows best at a temperature of 50 degrees C.
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Thermoregulation is the process of regulating body temperature.
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Thioglycolate broth is a culture medium that promotes favorable conditions for the growth of anaerobic bacteria.
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Thoracic means relating to the thorax, the upper part of the trunk between the neck and abdomen.
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The thoracic blood volume is the volume of blood located in the thorax. The thorax is the upper part of the trunk between the neck and the abdomen (the chest).
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Thoracolumbar relates to the thoracic and lumbar areas of the vertebral column.
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The thorax is the upper part of the trunk between the neck and the abdomen; the chest.
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Thrombolytic means breaking up or dissolving a clot in the cardiovascular system.
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Thrombosis is a condition in which the blood changes from a liquid to a solid state within the blood vessel and produces a blood clot or thrombus.
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Throughput is the output or production of a computer program over a period of time.
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The thymus is the primary lymphoid organ in the body, located over the heart and/or in the neck area. The thymus is enclosed in a capsule and divided internally by cross walls into many lobules, each full of T-lymphocytes (white blood cells associated with antibody production). T-lymphocytes migrate from the bone marrow to the thymus, where they mature and differentiate until activated. Athymic individuals lack T-cells.
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The thyroid is a large endocrine gland situated in the base of the neck; it is concerned with regulation of the metabolic rate.
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The thyroid gland is a highly vascular organ located at the front of the neck, which secretes the hormone thyroxine directly into the blood, and is a part of the endocrine system of ductless glands.
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Thyrotropin is a hormone secreted by the anterior pituitary; thyrotropin stimulates the thyroid gland. It is also called thyroid stimulating hormone (TSH). Thyrotropin is used as a diagnostic test to differentiate between primary and secondary hypothyroidism.
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Thyrotropin Releasing Factor (also known as TRH or Thyrotropin Releasing Hormone) is a hormone secreted by nerve endings in the hypothalamus and then transported to the anterior pituitary. TRH directly affects the anterior pituitary gland cells by increasing their output of thyroid-stimulating hormone, TSH, which has many important affects throughout the body -- one of which is control of metabolism.
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Thyrotropin Releasing Hormone (also known as TRF or Thyrotropin Releasing Factor) is a hormone secreted by nerve endings in the hypothalamus and then transported to the anterior pituitary. TRH directly affects the anterior pituitary gland cells by increasing their output of thyroid-stimulating hormone, TSH, which has many important affects throughout the body -- one of which is control of metabolism.
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Thyroxine, also referred to as T4, is one of the hormones synthesized and secreted by the thyroid gland; it acts to increase the rates of chemical reactions in almost all cells of the body, thus increasing the general level of body metabolism. Thyroxine can be administered by mouth to treat underactivity of the thyroid gland.
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The tibia is the shin bone, i.e., the inner and larger bone of the lower leg.
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The tibialis anterior is one of the two muscles in the leg that extend from the tibia, or shin bone, to the bones of the foot; this muscle turns the foot inward and flexes the toes backward.
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The tibiofibular junction is the junction between the tibia and fibula (bones of the lower leg).
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The tidal volume is the volume of air inspired or expired with each normal breath; normally about 500 ml.
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A tilt table test is a procedure used to determine if decreased blood flow to the head will initiate orthostatic intolerance, a condition associated with fainting. At the beginning of the test, the subject is asked to lie supine on a table. The table is then angled upward from the horizontal so that the subject is inclined to a near vertical position. During the test, symptoms are continuously monitored as well as electrocardiogram (ECG or EKG), heart rate, and blood pressure.
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A tilt-table is a medical examination table used to test othostatic intolerance by tilting a person head-up or head-down from the horizontal position. The table typically has a footboard and straps or handles to prevent the patient or subject from sliding off during examination.
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Time cues, which are present in everyday life, make it possible for plants and animals to recognize and respond to their environment. Examples of time cues include time of day, season of year, phase of the moon, etc.
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Time-integrated means summed or accumulated over a period of time.
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Titer is the concentration of a substance or the strength of such a substance.
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Torque is the turning effect produced when force is applied to a rotational axis.
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The Torque Velocity Dynamometer (TVD) measures torque, which is the turning effect produced when force is applied to a rotational axis. The contracting muscles associated with elbow and ankle joints apply force against a lever which measures the torque produced.
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Torsional eye movements are produced when the head rotates in the roll axis and are visual as a rotation of the eyeball with a sudden "jump" back in its original position.
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Total body water (TBW) is all the water in the body, including water inside and outside the cells, including water in the GI and urinary tracts.
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Total lung capacity (TLC) is the maximum volume to which the lungs can be expanded with the greatest possible inspiratory effort; it is equal to the vital capacity (VC) plus the residual volume (RV) and is approximately 5800 ml.
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Total peripheral resistance is the maximum degree of resistance to blood flow caused by constriction of the systemic blood vessels (normally about 100 mm Hg).
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Total sleep time is equal to the total rest-period time minus total time spent awake.
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Toxic means harmful, destructive or deadly.
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Toxicological refers to the study of poisons and the treatment of poisoning.
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Toxicology is the study of harmful substances called toxicants and their effect on organisms. More specifically, toxicologists study the molecular structure of toxicants; exposure of humans and animals to toxicants; absorption, distribution and bioprocessing of toxicants in the body; and pathologic conditions caused by toxicants.
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Toxigenic means to have the ability to produce toxin.
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A toxin is a poisonous substance. It can be a specific product of the metabolic activities of a living organism. Toxins in the body are typically capable of inducing antibody formation.
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A tracer is a substance that can be readily identified, such as an isotope, used to trace the course of a chemical or biological process or determine the size of a space that cannot be directly measured.
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Trajectory is the path traced by any body moving as a result of an externally applied force, considered in three dimensions. Trajectory is sometimes used to mean flight path or orbit , but orbit usually means a closed path and trajectory, a path which is not closed.
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A transducer is a device that receives energy from one system and transmits it, often in a different form, to another.
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Transduction is the transfer of energy from one system to another; often the energy is received by one system which retransmits it to another is a different form. Transduction can also refer to a method of genetic recombination by which DNA is transferred from one cell to another by a virus.
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Transearth coast denotes travel from the moon to Earth.
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A transfer function is a mathematical expression of the relationship between the input signal and output signal of a system.
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Transferrin is a protein that transports iron in the blood.
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Transient means to stay only a short time.
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Translocation is the breakage of a piece of a chromosome from the parent chromosome and reattachment of the chromosome piece to another chromosome.
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Translunar coast denotes travel from Earth to the moon.
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A transmitter is a chemical which a neuron uses to influence the activity of an anatomically adjacent cell body, such as a hair cell. A neurotransmitter is any one of numerous chemicals that modify or result in the transmission of nerve impulses between synapses. A transmitter can also refer to electronic equipment that generates and amplifies a carrier wave, modulates it with a meaningful signal, as derived from speech or other sources, and radiates the resulting signal from an antenna.
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Transpiration is the act or process of giving off vapor containing waste product through the stomata of plant tissue or pores of the skin.
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ATP is the abbreviation for adenosine 5'-triphosphate. One function of ATP is the active transport of ions and molecules across cell membranes. Transport ATP has specific affinities for only one or two substrates, meaning it can only transport a few specific molecules or ions across cell membranes.
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A treadmill is a device operated by walking on the moving steps of a wheel or treading an endless sloping belt.
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Thyrotropin Releasing Hormone (also known as TRF or Thyrotropin Releasing Factor) is a hormone secreted by nerve endings in the hypothalamus and then transported to the anterior pituitary. TRH directly affects the anterior pituitary gland cells by increasing their output of thyroid-stimulating hormone, TSH, which has many important affects throughout the body -- one of which is control of metabolism.
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Tri-iodothyronine (T3) is a hormone that helps regulate growth and development, helps control metabolism and body temperature, and, by a negative-feedback system, act to inhibit the secretion of thyrotropin by the pituitary.
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The triceps is a muscle with three heads of origin, particularly the triceps brachii, which is situated on the back of the upper arm and contracts to extend the forearm.
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The triceps surea is the "three-headed" calf muscle, composed of the one-headed soleus and the two-headed gastrocnemius muscles.
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Triglyceride is a compound consisting of a fatty acid (oleic, palmitric, or stearic) and glycerol. Triglycerides make up most animal and vegetable fats and are the principle lipids in the blood, where they circulate, bound to a protein, forming high- and low-density lipoproteins. The total amount of triglycerides and the amount, proportions, and kind of lipoproteins are important in the diagnosis of treatment of many diseases and conditions, including diabetes, hypertension, and heart disease.
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Triiodothyronine (T3) is one of the hormones synthesized and secreted by the thyroid. Normally synthesized in smaller quantities as thyroxine (T4), it has the same biological effects as thyroxine, but is more potent and the onset of its effects is more rapid.
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Tritiated thymidine is thymidine (a nitrogen-containing base linked to the sugar D-2-deoxyribose) in which some of the hydrogen atoms have been replaced with tritium (hydrogen-3). It is used as a tracer for measuring DNA synthesis.
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Tritium is a radioactive isotope of hydrogen with a nucleus composed of three neutrons and one proton; it is commonly used as a chemical tracer because it emits low levels of radioactivity.
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Trypsin is an enzyme secreted by the pancreas that continues the digestion of proteins by breaking down peptones into smaller peptide chains.
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Trypsinogen is the inactive form of trypsin, an enzyme secreted by the pancreas that continues the digestion of proteins by breaking down peptones into smaller peptide chains. Trypsinognen is converted to trypsin in the duodenum by the action of the enzyme enteropeptidase.
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Trypticase soy agar (TSA) is a blood agar base that can be used for the isolation and maintenance of all organisms except those with special nutritional requirements. It contains an inhibitor that keeps fungi from growing on the sample.
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Trypticase soy broth is a general purpose nutrient culture medium, which contains substrates for microbial growth such as pancreatic digest of casein, papaic digest of soybean meal, sodium chloride and water. Trypticase soy broth supports the growth of most organisms and can be used to generate mass quantities for biochemical tests; it can also be used to observe colony morphology, develop pure cultures, and determine bacterial quantities.
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The Tuberculin Skin Test is a test to determine past or present tuberculosis infection based on a positive skin reaction, using one of several methods. A purified protein derivative (PPD) if tubercle bacilli, called tuberculin, is introduced into the skin by scratch, puncture, or injection. If a raised, red or hard zone forms surrounding the tuberculin test site, the test is read as positive. However, a negative tuberculin reaction does not rule out a diagnosis of previous or active tuberculosis.
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Tuberculosis (TB) is an infectious disease caused by a bacteria, Myobacterium tuberculosis which may affect almost any tissue or organ of the body. The most common target of the disease, however, is the lungs.
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Tungsten is a gray-white heavy high-melting ductile hard polyvalent metallic element that resembles chromium and molybdenum in many of its properties and is used especially for electrical purposes and hardening alloys (as steel).
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Turbid means not clear.
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Turbidity means having sediment or foreign particles stirred up or suspended, usually within a liquid.
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The Torque Velocity Dynamometer (TVD) measures torque, which is the turning effect produced when force is applied to a rotational axis. The contracting muscles associated with elbow and ankle joints apply force against a lever which measures the torque produced.
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The tympanic membrane, or eardrum, is a thin semitransparent membrane that stretches across the ear canal and separates the outer and middle ear.
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Typhoid means pertaining to or resembling typhus. Typhus is any of a group of acute infectious diseases caused by various species of Rickettsia and usually transmitted from infected rodents to humans by the bites of lice, fleas, mites, or ticks. These diseases are all characterized by headache, chills, fever, malaise, and a maculopapular rash.
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Tyrosine is a white crystalline amino acid derived from the hydrolysis of protein, used as a growth factor in nutrition and as a dietary supplement.