R Flashcards
Radial Symmetry
A body plan in which any plane through the animal from oral/anterior to aboral/posterior generates mirror images.
Radiant Energy
Thermal energy released from an object in relation to its temperature.
Radiant Heat Transfer
The emission of thermal energy from a warm object to cooler surroundings.
Radiation
The emission of energy from an object.
Ram Ventilation
A ventilatory strategy in which the forward movement of the animal provides the propulsive force needed for bulk flow of the ventilatory medium across the respiratory surface. Seen in some fishes and insects.
Range Fractionation
A strategy in which groups of sensory neurons work together to increase the dynamic range of a receptor organ. Each neuron has an overlapping, but not identical, dynamic range, allowing a wider range of stimulus intensities to be coded by the population of receptors.
Rate Constant
The factor that allows the prediction of an enzymatic rate based on the concentration of the substrates.
Reaction Norm
The range of phenotypes that can be produced by a given genotype when it is exposed to different environments.
Reactive Oxygen Species (ROS)
A free radical in which the unpaired electron is associated with an oxygen atom.
Receptive Field
The area of the body that, when stimulated by an incoming sensory stimulus, affects the activity of a sensory neuron.
Receptor
A protein or cell that can detect an incoming stimulus.
Receptor Adaptation
The process by which sensory receptor cells become less sensitive to sensory signals as signal duration increases.
Receptor Potential
A graded change in the membrane potential within an epithelially derived sensory receptor cell. The receptor potential triggers the release of neurotransmitter onto a primary afferent neuron, causing a postsynaptic graded potential. If this postsynaptic potential exceeds threshold, it
will trigger action potentials in the axon of the primary afferent neuron.
Receptor Proteins
Proteins specialized for the detection of signals.
Receptor Enzymes
Defining feature of a class of signal transduction pathways in which the receptor acts as an enzyme that catalyzes a chemical reaction when activated.
Recruitment
The stimulation of different collections of muscle fibers in response to different activity patterns.
Rectal Gland
An organ found in cartilaginous fish that secretes salt to aid in osmotic regulation.
Redox Balance (reduction-oxidation balance)
A condition in which there is no net change in the ratio of reduced to oxidized reducing equivalents, typically NADH/NAD+.
Redox Shuttle
A multienzyme pathway used to transfer the energy of reducing equivalents from glycolysis into the mitochondria for oxidation.
Redox Status
The relative levels of reduced to oxidized molecules of interest; typically applied to metabolic biochemistry (e.g., NADH/NAD+) but can also be used to reflect the degree of oxidative stress.
Reducing Equivalents
NAD(P)H or FADH2.
Reductant
A molecule that donates an electron to another molecule (the oxidant). In doing so, the reductant becomes oxidized.
Reduction
A chemical reaction whereby a molecule accepts an electron from another molecule, becoming reduced.
Reductionism
A philosophical approach that asserts that complex processes can be understood in terms of their components.
Reflex Arc
A simple neural circuit that does not involve the conscious centers of the brain.
Reflex Behaviors
see reflex arc
Behaviors that do not require conscious input from the central nervous system.
Refraction
The bending of light as it passes from one medium to another.
Refractive Index
The degree to which a material refracts light.
Refractory Period
see also absolute refractory period, relative refractory period
A period in which an excitable cell is less likely to generate an action potential.
Regional Heterothermy
A thermoregulatory strategy in which regions of an animal’s body exhibit significantly different temperatures.
Regulators
Animals that maintain a degree of constancy in an internal physiochemical parameter (e.g., osmolarity or temperature) despite external changes in the parameter.
Regurgitation
The expulsion of stomach contents back up the esophagus into the oral cavity.
Relative Refractory Period
A period immediately following the absolute refractory period in which an excitable cell will generate an action potential only if exposed to a suprathreshold (unusually large) stimulus.
Relaxed Endothermy
A thermal strategy in which an endothermic animal allows its body temperature to fall for a period of time.
Renal
Pertaining to the kidney.
Renal Clearance
The removal of an entity from the plasma by the kidney.
Renal Corpuscle
A structure consisting of the glomerulus and Bowman’s capsule of a nephron in the vertebrate kidney.
Renal Tubule
Within a nephron, it is the tube composed of a single layer of transport epithelium. It is also known as a kidney tubule. It is the single filtration unit of the vertebrate kidney.
Repolarization Phase
A return of the membrane potential of a cell toward the resting membrane potential following a depolarization or hyperpolarization.
Residuals
The difference between the observed values and the values that would be predicted based on an underlying function. Often computed in the context of allometric scaling.
Resistance, Electrical
The force opposing the flow of charge through an electrical circuit.
Resistance, Vascular
The force opposing the flow of blood through the circulatory system.
Respiration
see also external respiration
The process by which mitochondria consume oxygen and produce carbon dioxide.
Respiratory Acidosis or Alkalosis
Decrease or increase in blood pH as a result of changes in blood carbon dioxide (usually as a result of changes in ventilation).
Respiratory Pigments
Metalloproteins that act as oxygen transport and storage molecules (e.g., hemoglobin).
Respiratory Pump
A mechanism that helps to pump blood back to the heart via the venous system as a result of the reduced pressure in the chest cavity during the inspiration phase of lung ventilation.
Respiratory Quotient (RQ)
The ratio of CO2 produced to O2 consumed; indicative of the type of fuel being utilized. An RQ of 0.7 indicates fatty acids are the fuel, whereas an RQ of 1.0 suggests carbohydrates are being oxidized.
Resting Membrane Potential
The membrane potential of an excitable cell when action potentials or graded potentials are not being generated.
Resting Metabolic Rate (RMR)
see also basal metabolic rate, standard metabolic rate
The metabolic rate of an animal at rest under experimentally defined conditions.
Rete Mirabile
A network of blood vessels that serve to retain heat via countercurrent exchange.
Retia (singular: rete)
Networks of blood vessels or nerves.
Retina
A layer of light-sensitive cells that lines the back of eyes.
Retinal
A derivative of vitamin A that acts as the light-absorbing chromophore in animal photopigments.
Reversal Potential
The membrane potential at which there is no net movement of an ion through open ion channels.
Reynolds Number
A dimensionless number associated with an object that reflects how smoothly a fluid flows over the surface of the object.
Rhabdomeric Photoceptors (see also ciliary photoreceptors)
One of two types of animal photoreceptor cells. Arthropod photoreceptors are rhabdomeric.
Rhodopsin
A photopigment consisting of the protein opsin chemically linked to a vitamin A derivative called retinal.
Ribosome
A complex of RNA and protein that carries out protein synthesis.
Rigor
A state of skeletal muscle in which crossbridges remain intact because ATP has been depleted from the cell.
RNA
polymer of ribonucleic acids similar to DNA except that they contain ribose in
place of deoxyribose and uracil in place of thymine; includes mRNA, tRNA, and rRNA. Involved in transferring information from DNA and in protein synthesis.
RNase
An enzyme that degrades RNA either from the end (exonuclease) or internally (endonuclease).
RNase
An enzyme that degrades RNA either from the end (exonuclease) or internally (endonuclease).
Rod
see also cone
A type of vertebrate photoreceptor cell. In mammals, rods are responsible for vision in dim light.
Root Effect
A change in the oxygen carrying capacity of blood as a result of changes in pH.
Round Window
Membrane at the end of the cochlea; acts as a pressure release for the fluid of the inner ear.
rRNA
The form of RNA that is incorporated into the riboprotein complex known as a ribosome.
R-Selection
A life history strategy whereby parents invest minimally in large numbers of offspring; best suited to rapidly exploit underutilized niches.
R-Type Strategy
A reproductive strategy where parents produce numerous offspring, with relatively little investment in their care.
Ryanodine Receptor (RYR)
A Ca2+ channel found in the sarcoplasmic reticulum of muscle, which allows Ca2+ to escape into the cytoplasm to initiate muscle contraction.
