V
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 XYZV(A)
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V(A) or alveolar gas volume is the total volume of gas in the lung region within which respiratory gas exchange occurs.
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V(C) is an acronym which stands for the volume of blood in the pulmonary alveolar capillaries.
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V(E) refers to the respiratory minute volume or the total amount of new air moved into the respiratory passages each minute. It is equal to the tidal volume times the respiratory rate (TV x RR), usually averaging about 6 liters per minute.
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Vagal pertains to the vagus nerve.
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The valsalva maneuver is an attempt to forcibly exhale with the nose and mouth closed.
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The Van Allen belts are two belts of trapped radiation, consisting mainly of protons and high-energy electrons, which exist at an altitude of approximately 556 km. The belts vary in altitude over various parts of the Earth, and are absent over the north and south poles. A particularly significant portion of the belts is a region called the South Atlantic Anomaly (SAA). Over this region, the geomagnetic field draws particles closer to the Earth than in other regions of the belts. These belts were discovered during the Explorer I mission in 1958.
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Vapor diffusion is the diffusion of vapor created from changing a liquid to a gas state of matter, and is a method of growing protein crystals.
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Variable gravity refers to conditions of different levels of gravity. Gravity is the force with which two bodies having mass are attracted to each other. The reference used to measure gravity forces is the standard sea-level Earth gravity which is called One-G (1-G). Certain devices, like centrifuges, can simulate variable gravity levels.
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Vascular means of or pertaining to the blood vessels.
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Vascular conductance is the ratio of blood flow through a blood vessel. The blood flow per unit of pressure difference is measured.
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Vascularization refers to the presence of blood vessels in biological tissues.
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Vasculature is the vascular network of an organ or the distribution of blood vessels in an organ or tissue.
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Vasoactive is tending to cause vasodilation or vasoconstriction.
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Vasoconstrictive means able to cause a constriction of blood vessels.
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The term vasodepressor means the reduction of tone in blood vessels with vasodilation and resulting lowered blood pressure.
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The term vasodilation means dilation of the blood vessels.
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Vasopressin (also called antidiuretic hormone, ADH) is a hormone produced and released in the posterior pituitary gland which causes the kidneys to retain water, thus increasing the water content of the body. In high concentrations, it causes the constriction of blood vessels throughout the body and consequent elevation of blood pressure.
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Vasopressor means producing constriction of the capillaries and arteries (vasoconstriction) and a rise in blood pressure, usually understood to be systemic arterial pressure unless otherwise specified. A vasopressor is also an agent that produces vasoconstriction.
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Vasovagal relates to the action of impulses in the vagus nerve on the circulation. The vagus reduces the rate at which the heart beats, and thus lowers its output.
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Vastus literally means "great muscle."
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The vastus intermedialis is one of the three muscles that form part of the quadriceps muscle of the thigh, located at the front of the thigh.
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VCO2 max is an abbreviation used to indicate maximum carbon dioxide production.
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Ventilation Exchange (VE) is the exchange of gases, primarily oxygen and carbon dioxide, during the passage of air into and out of the respiratory passages.
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Vection is the sensation of self-rotation in the opposite direction of a provided (rotating) stimulus.
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Vectorcardiogram is a tracing of the direction and magnitude of the electrical forces of a heart's activity during a cardiac cycle. It is produced by simultaneous recording of three standard leads, using an oscilloscope.
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Vectorcardiography is a form of electrocardiography in which the electrodes are placed on the body in specific positions to determine the direction of the heart's action currents.
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Velocity is the rate of movement, or more specifically, the distance traveled per unit of time.
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Venomotor means causing change in the caliber (the diameter of the inside) of a vein.
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Venous means relating to the veins, blood vessels which carry blood toward the heart. All veins, except the pulmonary vein, carry blood that contains no oxygen, thus giving it a bluish color.
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Venous compliance is the change in blood volume for a given change in pressure produced by a cuff around the arms or legs. The cuff pressure restricts blood flow from the tissues and causes the blood to pool.
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Venous pressure is the blood pressure in the veins of the body.
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Ventilation is the passage of air into and out of the respiratory tract.
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Ventilation Exchange (VE) is the exchange of gases, primarily oxygen and carbon dioxide, during the passage of air into and out of the respiratory passages.
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The ventilation-perfusion ratio is the relationship between lung ventilation and pulmonary blood flow in the lung tissue.
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Ventral means relating to, situated at, or close to the front of the body or to the anterior part of an organ.
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Ventricular means relating to a ventricle, which is the name of certain cavities of the heart and brain.
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Vertebral bodies support most of the axial load of the normal spine and consist of the thoracic and lumbar vertebrae.
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Vertebrates are organisms that have a spinal column or backbone. This includes fish, amphibians, reptiles, birds and mammals.
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Vertex is the highest point of something; apex. The crown or top of the head.
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Vertigo is a disabling sensation in which the affected individual feels that either he, himself or his surroundings are in a state of constant movement. It is most often a spinning sensation, but there may be a feeling that the ground is tilting.
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Vestibular means relating to the vestibule of the ear, a cavity situated at the entrance to the bony labyrinth (a part of the inner ear) that contains the saccule and utricle -- the organs of equilibrium.
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The vestibular apparatus is the organ that detects sensations concerned with equilibrium; it is composed of a system of bony tubes and chambers in the petrous portion of the temporal bone called the bony labyrinth. The inner ear structures that are associated with balance and position sensing. It includes the vestibule and semicircular canals.
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The vestibular organ detects sensations concerned with equilibrium; it is composed of a system of bony tubes and chambers in the petrous portion of the temporal bone called the bony labyrinth. The inner ear structures that are associated with balance and position sensing. It includes the vestibule and semicircular canals.
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The vestibular sled was a device flown on Spacelab missions that was designed to test the functional organization of the human vestibular apparatus and orientation system, as well as the vestibular adaptation processes to microgravity. The sled used during the D-1 mission was configured with a seat for the test person which could be moved backwards and forward on mounted rails with precisely adjusted accelerations.
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The vestibular system is made up of a cavity situated at the entrance to the bony labyrinth in the inner ear which contains the tiny organs governing equilibrium and balance -- the saccule and utricle.
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The vestibulo-ocular reflex (VOR) responds to the rotation of the head with eye movements in the opposite direction. This reflex allows you to maintain a fixed gaze on an object even though your head may be in motion.
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The vestibulo-ocular reflex (VOR) is the reflex movement of the eyes in the opposite direction to that in which the head is moved. The nerve signals that cause the reflex originate in the vestibular organs of the inner ear.
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The vestibulocochlear cranial nerve is one of the 12 pairs of nerves that arise directly from the brain and leave the skull through separate apertures. Also called the eighth cranial nerve, the vestibulocochlear cranial nerve is responsible for carrying sensory impulses from the inner ear to the brain. It thus has two branches, the vestibular nerve and the cochlear nerve. The cochlear nerve carries impulses from the ear and is therefore the nerve of hearing, while the vestibular nerve serves equilibrium, carrying impulses from the semicircular canals, utricles, and saccules with information about posture, movement and balance.
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VHM or Voluntary Head Movements, refers to head movements that are made voluntarily.
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Viability refers to the capability of living.
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Viable means capable of developing, growing and otherwise sustaining life; capable of life.
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Vibration is a rapid back and forth motion of a particle or solid.
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Vibrocardiogram is a tracing of the vibrations of the heart sounds made by an apparatus consisting of a microphone actuating a cathode ray.
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Virology is the study of viruses and viral diseases.
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Virulence is the disease-evoking power of a microorganism in a given host.
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A virus is any member of a large group of submicroscopic infective agents, regarded either as extremely simple microorganisms or as extremely complex molecules, that typically contain a protein coat surrounding an RNA or DNA core of genetic material but no semipermeable membrane, that are capable of growth and multiplication only in living cells, and that cause various important diseases in humans, lower animals, or plants. Viruses replicate by releasing their DNA or RNA into the host cell; the viral DNA or RNA in turn directs the host cell's "machinery" to churn out more viral DNA or RNA. Classification of viruses depends on mode of transmission, host range, symptoms and other factors.
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Visceral means of, or pertaining to, or affecting the viscera. Viscera is a term used to refer to the organs in the cavities of the body, especially those in the abdominal cavity. Examples include organs of the digestive, respiratory, urogenital, and endocrine systems as well as the spleen, the heart, and great blood vessels.
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Visual refers to the sense of vision, the sense that enables perception of objects in the environment by means of the eyes.
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Visual acuity refers to the measure of the sharpness of vision.
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The visual cortex is the part of the brain that detects the forms of objects, brightness of the individual parts of the objects, shading, and spatial organization of the visual scene.
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The visual field is the area simultaneously visible to one eye without movement; often measured by means of an arc (perimeter) located 330 mm from the eye.
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Visual phosphenes are best described as subjective sensations of flashes of light; they are thought to result from radiation damage to the brain or eye.
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Visuo-motor means both visual and motor, i.e., a nerve with both functions.
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Vital capacity (VC) is the maximum amount of air that a person can expel from the lungs after first filling the lungs to their maximum extent; it is equivalent to the inspiratory reserve volume (IRV) plus the tidal volume (TV) plus the expiratory reserve volume (ERV). (VC = IRV + TV + ERV)
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A vitamin is an organic molecule needed in trace amounts for normal growth and metabolic processes.
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Vitamin D is a fat-soluble vitamin that enhances the absorption of calcium and phosphorus from the intestine and promotes their deposition onto the bone.
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Vitamin D metabolites are slight variations of the vitamin D hormone which are formed by the addition of hydroxyl groups (OH) when vitamin D is metabolized in the liver and kidney. Metabolites of vitamin D are the biologically active forms of the molecule.
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Maximum rate of oxygen uptake per minute.
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Void means to empty or evacuate waste from the body. For instance, throughout the day, the human being excretes urine several times; each of these is called a void. The composition of urine changes in a cycle every 24 hours. The first void in the morning contains many minerals, electrolytes and metabolism-end products. During the day, the amount of dissolved substances is reduced.
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Volatile means evaporating readily at normal temperatures and pressures, i.e., capable of being readily vaporized.
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Volitional means voluntary, or done by an act of will.
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The volume of inspired oxygen is the maximum oxygen uptake per minute by the lungs, and is usually referred to as VO2 Max.
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Volume-regulatory mechanisms is a term that refers to all mechanisms that result in an increase or reduction of body fluids, mainly intracellular fluids such as blood plasma.
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Voluntary means relating or acting in obedience to the will; not obligatory.
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Vortex means fluid flow involving rotation about an axis.