I Flashcards
I-Band (isotropic band)
The region of a muscle sarcomere where the thin filaments that span a Z-disk do not overlap with the thick filament.
ice-Nucleating Agent
A molecule or particle that initiates the formation of ice at a subfreezing temperature.
Ideal Gas Law
The relationship between pressure, volume, and gas concentration.
Ileum
The last section of the small intestine, connecting the jejunem to the large intestine.
Imidazole Group
The amino group found in histidine and other compounds that exhibits a pK value near physiological pH, and is therefore important in the buffering of the pH of body fluids.
Immunocompetence-Handicap Hypothesis
A hypothesis that suggests displays are physiologically expensive and they are as elaborate as the animal can tolerate without compromising its health.
Immunological Memory
After exposure to a pathogen, animals with acquired immunity retain the cells needed to produce antibodies to that specific antigen. When the antigen reappears, the cells can rapidly proliferate and produce antibody.
In situ
An in vitro condition in which the parameter under investigation is in a realistic setting.
In vitro
Occurring outside a living animal or cell.
In vivo
Occurring within a living animal or cell.
Inactivation Gate
One of the two gates that open and close voltage-gated sodium channels.
Incipient Lower Lethal Temperature (ILLT)
For a poikilotherm acclimated to a given temperature, it is the lowest temperature that can be tolerated.
Incipient Upper Lethal Temperature (IULT)
For a poikilotherm acclimated to a given temperature, it is the highest temperature that can be tolerated.
Incus (anvil)
One of the three small bones of the mammalian middle ear.
Indirect Calorimetry
Estimation of metabolic rate (heat production) using consumption of oxygen or production of carbon dioxide.
Induced Ovulation
Ovulation that is triggered in response to an external stimulus, such as copulation.
Inducible
Usually refers to a gene that can increase in expression in response to regulatory conditions; can be applied to the encoded protein itself, as in “an inducible enzyme.”
Inertial Effects
The forces that resist a change in the movement of an object. Combines with viscous effects to determine the Reynolds number.
Inflammation
A element of an immune response associated with local heat production.
Inflammatory Response
Local changes sparked by tissue damage, including increased blood
flow, changes in vascular permeability to cells and fluids, recruitment of immune cells, and in some cases, elevated tissue temperature.
Ingested Energy
Term used to describe the total energy content of a diet, includes both digestible energy and indigestible energy.
Inhibin
A hormone involved in the regulation of follicle-stimulating hormone (FSH).
inhibitory Postsynaptic Potential (IPSP)
An inhibitory potential in a postsynaptic cell.
Inhibitory Potential
A change in the membrane potential that makes an excitable cell (neuron or muscle) less likely to generate an action potential.
Innate Immune System
see adaptive immune system
A type of immune system found in all animals. One of two components
of the immune system of vertebrates.
Inner Ear
A series of membranous sacs that contain the organs of hearing and balance in vertebrates.
Inner Hair Cells
see also outer hair cells
One of two types of hair cells found in the organ of Corti in the inner ear of mammals; involved in the sense of hearing.
Inorganic Ion
An ion lacking carbon atoms.
Inorganic Ion
An ion lacking carbon atoms.
Inositol Trisphosphate (IP3)
A second messenger in the phosphatidylinositol signaling system.
Inspiration
Inhalation.
Instar
A juvenile form of an insect that resembles the adult form in gross appearance.
Insulation
An external or superficial layer of material that reduces the heat loss from the animal to the environment, such as fur, feathers, and blubber.
Insulin
Peptide hormone that homeostatically regulates blood glucose levels; released in response to increased blood glucose.
Integral Membrane Protein
A protein that is embedded within a cellular membrane, and can only be released with detergent treatment that disrupts the membrane.
Integrating Center
The part of the nervous system that takes in afferent sensory information and processes it to send out efferent signals; for example, the brain.
Integrins
A class of dimeric transmembrane proteins that is important in the interactions betweens cells and the extracellular matrix, mediating both adhesion and cell signaling.
Integument
The outer layer of an animal, usually derived from epithelial cells and their secretions.
Intercalated Disc
The intercellular contact between cardiomyocytes composed of gap junctions and desmosomes.
Intermediate Filaments
One class of proteins that are used to make up the cytoskeleton.
Interneuron
A neuron that makes synaptic connections between other neurons.
Internode
The region of axonal membrane that is covered with the myelin sheath.
Interstitial Fluid
The component of the extracellular fluid that exists between cells.
Intracellular Receptors
Receptors that are located inside the cell, rather than the cell membrane.
Intrapleural Pressure
The pressure within the pleural cavity that surrounds the lungs of mammals.
Intron
A region of DNA that is always spliced out of the mRNA following transcription.
Inulin
A molecule that is used to assess glomerular filtration rate because it is neither secreted nor recovered by the kidney tubule.
Ion
An atom or molecule with a net charge.
Ion Channels
Transmembrane proteins that permit transfer of ions or molecules through an aqueous pore down an electrochemical gradient.
Ionic Bond
A weak bond between an anion and a cation.
Ionoconformer
An animal with an internal ion profile that resembles the ion composition of the external water.
Ionophore
A molecule that forms pores within membranes, allowing specific ions to cross.
Ionoregulator
An animal that maintains an internal ion profile independent of the ion composition of the external water.
Ionotropic Receptor
A receptor protein that acts as a gated ion channel.
Iris
A ring of tissue located immediately in front of the lens of a vertebrate eye that controls the amount of light entering the eye by altering the size of the pupil.
Ischemia
A reduction in blood flow, depriving a tissue of oxygen and nutrients.
Islets of Langerhans
Clusters of endocrine cells in the pancreas that produce the hormones glucagon and insulin.
Isocortex
The outer layer of the forebrain in mammals.
Isoelectric Point
The pH at which an ionizable molecule exhibits no net charge.
Isoform
A protein that has the same function as another protein but differs in primary sequence either because it is encoded by a different gene, or because it results from alternative promoter usage or differential splicing (contrast with alleles).
Isometric Contraction
A muscular contraction that results in force production without a change in length.
Isometric Muscles
Muscles that are arranged in a way that contraction does not lead to a change in length.
Isopleth
A contour line showing the value of a function of two variables connecting the points where the function has a particular value; e.g., the relationship between pH and bicarbonate concentration as described by the Henderson-Hasselbalch equation.
Isosmotic
Describes two solutions with the same osmolarity.
Isotonic
A solution with a profile and concentration of solutes that does not result in a change in the volume of a cell.
Isotonic Contraction
A muscular contraction that results in shortening without force production.
Isovolumetric Contraction
or isovolumic contraction
A phase during the cardiac cycle in which the heart contracts, but does not eject blood because the valves are closed, and thus does not change in volume.
Isovolumetric Relaxation
A phase of the cardiac cycle when the ventricle relaxes without a change in volume.
Isozyme
An isoform of an enzyme.
