D Flashcards
Dalton’s Law of Partial Pressures
The total pressure of a gas mixture is the sum of the partial pressures of the constituent gases.
Dead Space
The portion of the respiratory system containing gas that does not participate in gas exchange; the sum of the anatomical and physiological dead spaces.
Deamination
Removal of an amino group from a molecule, usually an amino acid.
Defecation
The expulsion of feces.
Defensin
A widespread protein that is cytotoxic to microbial pathogens, incorporated into the pathogen cell membrane to create a pore that permits movement of ions, killing the target cell.
Dehydrogenase
A class of enzymes that involves an exchange of electrons between a substrate and product.
Delayed Implantation
A reproductive strategy in which a fertilized ovum fails to implant
in the uterus, thereby delaying embryonic growth until external conditions are favorable.
Denature
The loss of three-dimensional structure (unfolding) of a complex macromolecule, such as protein or nucleic acid.
Dendrites
The branching extensions of a neuronal cell body that carry signals toward the cell body.
Dendritic
A tree-like pattern of branching.
Dendrodendritic Synapse
A synapse formed between the dendrites of two neurons.
Deoxyhemoglobin
Hemoglobin that is not bound to oxygen.
Depolarization
A change in the membrane potential of a cell from its normally negative resting membrane potential to a more positive value; a relative increase in the positive charge on the inside of the cell membrane.
Depolarization-Induced Ca2+ Release
A mode of muscle activation in which calcium crossing the sarcolemma through a Ca2+ channel causes a depolarization of the membrane, which directly opens a Ca2+ channel in the sarcoplasmic reticulum.
Depolarization Phase
The initial part of an action potential during which the electrical
difference across the membrane becomes smaller (the membrane potential becomes less negative).
Desmosome
A type of cell-cell junction common in epithelial tissues.
Diabetes Mellitus
A metabolic condition involving defects in insulin secretion or signal transduction that lead to abnormal regulation of blood glucose. There are two main types of diabetes mellitus: insulin-dependent (type 1) and non-insulin-dependent (type 2).
Diacylglycerol (DAG, or diglyceride)
A second messenger in the phosphatidylinositol signaling system.
Diadromous
A life history strategy of fish that includes movement from freshwater to seawater to breed (catadromous) or vice versa (anadromous).
Diaphragm
A sheetlike group of muscles that separates the thoracic and abdominal cavities of mammals.
Diastole
The portion of the cardiac cycle in which the heart is relaxing.
Diastolic Pressure
The arterial blood pressure during cardiac diastole.
Dichromats
Vertebrates with two types of receptors involved in color vision that detect
different parts of the visible spectrum.
Dietary Water
Water that comes into the animal preformed, in contrast to water that arises during the digestive process (metabolic water).
Diffusion
The net movement of a molecule throughout the available space from an
area of high concentration to an area of low concentration.
Diffusion Coefficient
A parameter that reflects the ability of an ion or molecule to diffuse.
Diffusivity
The ability of solutes to move through a solution by diffusion.
Digastric Stomach
A two-compartment stomach found in ruminants; each of the two compartments is further divided into two chambers.
Digestible Energy
The proportion of ingested energy that can be further processed, leaving
only indigestible material.
Digestion
The breakdown of nutrients in the gastrointestinal tract.
Digestive Enzymes
Hydrolytic enzymes secreted into the lumen of the gastrointestinal tract by
the digestive epithelium and accessory glands.
Dihydropyridine Receptor (DHPR)
The Ca2+ channel found in muscle plasma membrane, so named because of its ability to bind members of the dihydropyridine class of drugs.
Dimer
A combination of two monomers, typically in the context of protein structure. A homodimer has two identical monomers, and a heterodimer has two dissimilar monomers.
Diploblastic
A reference to the two germinal cell layers that are characteristic of cnidarians and ctenophores.
Dipnoan
A group of sarcopterygian fish commonly called lungfish, most closely related to the fish ancestor of amphibians.
Dipole
A molecule with both partial positive (δ+) and partial negative (δ−) charges resulting from the asymmetrical distribution of electrons.
Direct Calorimetry
Measurement of heat production; in the context of animal physiology, a measure of metabolic rate.
Disaccharide
A sugar composed of two
monosaccharides.
Discontinuous Gas Exchange
A ventilatory patternseen in some insects in which prolonged periods of apnea are followed by brief but rapid ventilation of the tracheal system.
Dissociation Constant (K_d)
A measure of the tendency of a complex to dissociate into its components; calculated as the ratio of the product of the concentrations of the dissociated components to the concentration of the complex once the reaction reaches equilibrium (e.g., for the reaction AB Δ A + B, Kd = [A][B]/[AB]).
Distal
A location furthest from a point of reference.
Opposite of proximal.
Distal Tubule
The region of a vertebrate kidney tubule just before the collecting tubules.
Disulfide Bridge
(also known as a disulfide bond
A covalent bond between two sulfhydryl groups, denoted as –S–S–.
Diuresis
The process of urine formation.
Diuretic
An agent that promotes urine
formation.
Dive Response
A collection of physiological responses to forced diving in air-breathing animals.
Divergence
A pattern in a neural pathway in which a single presynaptic neuron forms synapses with multiple postsynaptic neurons.
Diving Bradycardia
A reduction in heart rate as a result of submergence in air-breathing animals.
DNA
deoxyribonucleic acid
A polymer of nucleotides that acts as the genetic template.
DNA Microarray
A high-throughput method of analyzing DNA or RNA.
Donnan Equilibrium
The chemical equilibrium reached between two solutions separated from each other by a membrane permeable to some of the ions in the solutions.
Dopamine
A neurotransmitter (biogenic amine) produced in various regions of the vertebrate brain.
Dormancy
see also estivation, hibernation, and torpor
A general term for hypometabolic states accompanied by a reduction in activity.
Dorsal Horn
A region of gray matter within the spinal cord located on the dorsal side.
Dorsal Root
The dorsal of the two branches of a vertebrate spinal nerve as it enters the spinal
cord. Contains afferent neurons.
Dorsal Root Ganglion
Clusters of afferent cell bodies of neurons in the spinal nerves. Located adjacent to the spinal cord.
Doubly Labeled Water
An isotopic variant of water (H2O), where a less common isotope is used for both 1H (2H or 3H) and 16O (18O).
Used to measure field metabolic rate.
Down-Regulation
see also up-regulation
A decrease in the amount or activity of a protein or process;
e.g., a decrease in receptor number or activity on a target cell.
Drag
A force that resists the forward movement
through a fluid through interactions with the
surface of an object.
Drag Coefficient
A dimensionless parameter that is used to measure the amount of resistance as an object moves through a fluid.
Dual Breather
Also called a bimodal breather
An animal that can breathe either
air or water.
Duodenum
The most proximal region of the small intestine, directly following the stomach.
Duty Cycle
In cytoskeletal movement, the proportion of time in a cross-bridge cycle that a motor protein binds its cytoskeletal tract.
Dynamic Range
The range between the minimum and maximum signal that can be discriminated by a sensory receptor.
Dynein
see also kinesin
Motor protein that works in combination
with microtubules, usually moving in
the minus direction.
Dynein Arms
The motor proteins that extend from microtubules in the axoneme of cilia and flagella.
Dyspnea
The sensation of difficulty with breathing.
