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.