V

Question 1

Vagus Nerve

Answer 1

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.

Question 2

van der Waals Force

Answer 2

A type of weak bond forming from the mutual attraction of the nuclei of two atoms in a molecule.

Question 3

Vas Deferens

Answer 3

The duct through which sperm are carried from the sites of synthesis in the epididymis to the ejaculatory opening.

Question 4

Vasa Recta

Answer 4

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.

Question 5

Vascular Endothelium

Answer 5

Thin layer of cells that lines blood vessels.

Question 6

Vasculature

Answer 6

The blood vessels of the circulatory system.

Question 7

Vasoconstriction

Answer 7

Narrowing of a blood vessel as a result of contraction of the vascular smooth muscle; decreases local blood flow.

Question 8

Vasodilation

Answer 8

Widening of a blood vessel as a result of relaxation of the vascular smooth muscle; increases local blood flow.

Question 9

Vasomotion

Answer 9

Change in the diameter of blood vessels; also known as angiokinesis.

Question 10

Vasomotor Response

Answer 10

The changes in diameter of blood vessels in response to vasodilatory or vasoconstricting factors; also known as the angiokinetic response.

Question 11

Vasomotor Tone

see also venomotor tone

Answer 11

The degree of contraction of the smooth muscles surrounding the arterioles.

Question 12

Veins

Answer 12

Blood vessels that return blood to the heart. In vertebrates, blood flows from the capillaries into venules and then into veins.

Question 13

Venae Cavae (singular: vena cava)

Answer 13

A large vein that carries deoxygenated blood to the heart of vertebrates.

Question 14

Venomotor Tone

see also vasomotor tone

Answer 14

The degree of contraction of the smooth muscles surrounding the veins.

Question 15

Venous Return

Answer 15

The return of blood to the vertebrate heart via the venous system.

Question 16

Ventilation

Answer 16

Active movement of the respiratory medium (air or water) across the respiratory surface.

Question 17

Ventilation-Perfusion Ratio

or ventilationperfusion matching

Answer 17

The relationship between the ventilation (flow of respiratory medium) and the perfusion (flow of blood) at a respiratory surface.

Question 18

Ventral Horns

Answer 18

The gray matter portions of the spinal cord that extend to the front.

Question 19

Ventricle

Answer 19

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).

Question 20

Ventricular Ejection

Answer 20

The process of pumping blood out of the ventricles of the heart.

Question 21

Venules

Answer 21

Small blood vessels located between capillaries and veins.

Question 22

Vertebral Column

Answer 22

The series of vertebrae extending from the base of the skull to the tip of the tail in vertebrates.

Question 23

Vesicle

Answer 23

A membrane-bound compartment that buds off from the intracellular membranous network, often encased in coat proteins such as clathrin.

Question 24

Vestibular Apparatus

Answer 24

The organ of balance in the vertebrates.

Question 25

Villi

Answer 25

Undulations and folds in a tissue that serve to increase surface area; most commonly seen in the gastrointestinal tract.

Question 26

Viscosity

Answer 26

An internal property of a fluid that results in resistance to flow. Thick liquids have high viscosity.

Question 27

Viscous Effects

Answer 27

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.

Question 28

Visual Cortex

Answer 28

A part of the vertebrate brain that is responsible for processing visual signals.

Question 29

Visual Field

Answer 29

The area that is visible to an eye, without changing eye position.

Question 30

Vital Capacity

Answer 30

The maximum amount of respiratory medium that can be moved into or out of the respiratory system with each breath.

Question 31

Vitamin

Answer 31

A dietary compound that serves as a precursor for prosthetic groups of proteins, particularly enzymes.

Question 32

Vitellin

Answer 32

The dominant protein found in yolk produced from vitellogenin.

Question 33

Vitellogenin

Answer 33

The major protein in the yolk of an egg.

Question 34

Vitreous Humor

Answer 34

A thick gel that fills the space between the lens and the retina of the vertebrate eye.

Question 35

Viviparous

see oviparous and ovoviviparous

Answer 35

Animal whose offspring develop internally and are released as active young.

Question 36

V_max

Answer 36

The maximal rate of catalysis by an enzyme; arises when all substrates are at optimal (saturating) concentrations and prior to the formation of product.

Question 37

V_O2max

Answer 37

The maximal sustainable rate of oxygen consumption exhibited by an animal. The experimental means to assess V_O2max differs among disciplines.

Question 38

Volatile Fatty Acids

or short chain fatty acids

Answer 38

Fatty acids of chain length less than 2–6 carbons.

Question 39

Voltage Clamp

Answer 39

A technique used by neurophysiologists to study ion channel function in which the membrane potential is held constant.

Question 40

Voltage-Gated Ion Channel

Answer 40

A membrane protein containing an aqueous pore that can be opened in response to changes in the membrane potential.

Question 41

Vomeronasal Organ

Answer 41

A vertebrate sense organ adjacent to the mouth and nasal cavities that is involved in detecting pheromones.

Question 42

VU/P Ratio

Answer 42

The ratio of an ion or molecule concentration in the urine (U) versus the plasma (P).