V Flashcards
Vagus Nerve
The 10th cranial nerve of vertebrates; in mammals, innervates the pharynx, larynx, trachea, lungs, heart, esophagus, and intestinal tract; contains motor, parasympathetic, and sensory neurons.
van der Waals Force
A type of weak bond forming from the mutual attraction of the nuclei of two atoms in a molecule.
Vas Deferens
The duct through which sperm are carried from the sites of synthesis in the epididymis to the ejaculatory opening.
Vasa Recta
The straight blood vessels arranged in a hairpin loop that run from kidney cortex to medulla and back to the cortex. The countercurrent arrangement allows removal of salts and water from the peritubule interstitium while maintaining intramedullary osmotic gradients.
Vascular Endothelium
Thin layer of cells that lines blood vessels.
Vasculature
The blood vessels of the circulatory system.
Vasoconstriction
Narrowing of a blood vessel as a result of contraction of the vascular smooth muscle; decreases local blood flow.
Vasodilation
Widening of a blood vessel as a result of relaxation of the vascular smooth muscle; increases local blood flow.
Vasomotion
Change in the diameter of blood vessels; also known as angiokinesis.
Vasomotor Response
The changes in diameter of blood vessels in response to vasodilatory or vasoconstricting factors; also known as the angiokinetic response.
Vasomotor Tone
see also venomotor tone
The degree of contraction of the smooth muscles surrounding the arterioles.
Veins
Blood vessels that return blood to the heart. In vertebrates, blood flows from the capillaries into venules and then into veins.
Venae Cavae (singular: vena cava)
A large vein that carries deoxygenated blood to the heart of vertebrates.
Venomotor Tone
see also vasomotor tone
The degree of contraction of the smooth muscles surrounding the veins.
Venous Return
The return of blood to the vertebrate heart via the venous system.
Ventilation
Active movement of the respiratory medium (air or water) across the respiratory surface.
Ventilation-Perfusion Ratio
or ventilationperfusion matching
The relationship between the ventilation (flow of respiratory medium) and the perfusion (flow of blood) at a respiratory surface.
Ventral Horns
The gray matter portions of the spinal cord that extend to the front.
Ventricle
A fluid-filled sac or cavity
(e.g., the spaces in the center of the vertebrate brain;
the muscular pumping chambers of the vertebrate heart).
Ventricular Ejection
The process of pumping blood out of the ventricles of the heart.
Venules
Small blood vessels located between capillaries and veins.
Vertebral Column
The series of vertebrae extending from the base of the skull to the tip of the tail in vertebrates.
Vesicle
A membrane-bound compartment that buds off from the intracellular membranous network, often encased in coat proteins such as clathrin.
Vestibular Apparatus
The organ of balance in the vertebrates.
Villi
Undulations and folds in a tissue that serve to increase surface area; most commonly seen in the gastrointestinal tract.
Viscosity
An internal property of a fluid that results in resistance to flow. Thick liquids have high viscosity.
Viscous Effects
The antagonism to movement of an object due to the interaction of its surface with the fluid through which it moves. Combines with inertial effects to determine the Reynolds number.
Visual Cortex
A part of the vertebrate brain that is responsible for processing visual signals.
Visual Field
The area that is visible to an eye, without changing eye position.
Vital Capacity
The maximum amount of respiratory medium that can be moved into or out of the respiratory system with each breath.
Vitamin
A dietary compound that serves as a precursor for prosthetic groups of proteins, particularly enzymes.
Vitellin
The dominant protein found in yolk produced from vitellogenin.
Vitellogenin
The major protein in the yolk of an egg.
Vitreous Humor
A thick gel that fills the space between the lens and the retina of the vertebrate eye.
Viviparous
see oviparous and ovoviviparous
Animal whose offspring develop internally and are released as active young.
V_max
The maximal rate of catalysis by an enzyme; arises when all substrates are at optimal (saturating) concentrations and prior to the formation of product.
V_O2max
The maximal sustainable rate of oxygen consumption exhibited by an animal. The experimental means to assess V_O2max differs among disciplines.
Volatile Fatty Acids
or short chain fatty acids
Fatty acids of chain length less than 2–6 carbons.
Voltage Clamp
A technique used by neurophysiologists to study ion channel function in which the membrane potential is held constant.
Voltage-Gated Ion Channel
A membrane protein containing an aqueous pore that can be opened in response to changes in the membrane potential.
Vomeronasal Organ
A vertebrate sense organ adjacent to the mouth and nasal cavities that is involved in detecting pheromones.
VU/P Ratio
The ratio of an ion or molecule concentration in the urine (U) versus the plasma (P).
