M Flashcards
Macula Densa
A group of cells in the juxtaglomerular apparatus that senses the sodium chloride concentration of the tubular fluid.
Macrophage
A type of white blood cell that ingests foreign invaders and dead or dying cells.
Magnetite
A crystalline aggregation of a magnetic metal (usually iron); found in some magnetoreceptors.
Magnetoreceptor
A sensory receptor that responds to magnetic fields.
Malleus (hammer)
One of the three small bones of the mammalian middle ear involved in transmitting sound vibrations to the inner ear.
Malpighian Tubule
The functional equivalent of a kidney tubule in insects, releasing the urine into the gut.
Mannose-Binding Lectin
A protein secreted from the liver into the blood, which binds to mannose moieties of pathogens, enabling the pathogen to be recognized, an example of opsonization.
Mantle Cavity
A cavity formed by the body wall (mantle) of mollusks; generally contains the respiratory structures.
Mass Action Ratio
Ratio of products to substrates; when more than one product (or substrate) is involved, their concentrations are multiplied together. When a reaction is at equilibrium, the mass action ratio equals the equilibrium constant (K_eq).
Mass-Specific Metabolic Rate
The metabolic rate of an animal (usually described as oxygen consumption) expressed relative to body mass.
Mast Cells
Immune cells that release histamine when stimulated.
Mastication
Mechanical disruption of food in an oral cavity (chewing).
Maximum Velocity (Vmax)
The maximal enzymatic rate calculated from a substrate-velocity curve; can be estimated by the enzymatic rate observed when product is absent and substrate concentrations are optimal.
Maximum Velocity (Vmax)
The maximal enzymatic rate calculated from a substrate-velocity curve; can be estimated by the enzymatic rate observed when product is absent and substrate concentrations are optimal.
Mean Arterial Pressure (MAP)
The weighted average of the systolic and diastolic pressures, taking into account the relative length of each of these phases of the cardiac cycle.
Mechanical Energy
A form of energy arising from the movement or position of an object; can be either kinetic energy (as in a moving leg) or potential energy (as in a loaded spring).
Mechanogated Channel (or mechanically gated channel)
An ion channel that opens or closes in response to the stress (or stretch) on a membrane.
Mechanoreceptor
A sensory receptor that detects forces applied to cell membranes (such as touch or pressure). Can be used to describe either the receptor protein or cells containing these receptors.
Medulla Oblongata (Also called the medulla)
A region of the vertebrate brainstem containing centers that regulate heart rate, breathing depth and frequency, and blood pressure.
Medullary Cardiovascular Control Center
The region within the medulla that regulates cardiac-function.
Medullary Respiratory Center
The region within the medulla that regulates breathing depth and frequency.
Melanopsin
A photopigment found in the retinal ganglion cells of the vertebrate eye.
Melatonin
A hormone found in all animal groups that regulates sleep-wake cycles.
Melting Point
The temperature at which a solid can become a liquid; when the melting point and the freezing point are not the same temperature, this hysteresis suggests the presence of a solute that acts in a noncolloidal manner, such as an antifreeze protein.
Membrane Fluidity
A state that allows the two-dimensional movement of lipids and proteins within a lipid bilayer membrane.
Membrane Potential
The electrical gradient across a cellular membrane.
Membrane Recycling
The exchange of membrane lipids and protein between the plasma membrane and the internal membrane network.
Memory B Cells
A subclass of B cell lymphocytes that become quiescent but retain the ability to produce specific antibodies, conferring immunological memory.
Menarche
The age at which a female mammal with a menstrual cycle experiences her first menstruation.
Meninges
Membranes covering the vertebrate central nervous system. Mammals have three meninges; birds, reptiles, and amphibians have two; and fish have one.
Menses
In female mammals, the periodic shedding of the endometrial layer of uterine tissue that occurs if there is no implantation of a fertilized ovum; also known as menstruation.
Menstrual Cycle
The estrous cycle of humans and some other primates.
Mesangial Cells
Contractile cells between the capillaries of the glomerulus, which control blood flow, and thereby control blood pressure within the glomerulus.
Mesoderm
The middle of the three primary germ layers in a developing embryo; eventually gives rise to tissues such as bone, muscle, and connective tissue.
Metabolic Acidosis or Alkalosis
A decrease or increase, respectively, in blood pH as a result of metabolic activity.
Metabolic Depression
A reduction in metabolic rate below resting levels; associated with a period of dormancy.
Metabolic Flux
The flow rate through a metabolic pathway.
Metabolic Rate
The rate of heat production by a tissue or organism, usually approximated by oxygen consumption or carbon dioxide production.
Metabolic Theory of Ecology
An extension of the theory of allometric scaling of metabolic rate with body size that attempts to make predictions about processes at higher levels of biological organization (e.g., populations and communities).
Metabolic Water
The water produced by the metabolic breakdown of macromolecules.
Metabolism
The sum of all chemical reactions in a biologic entity.
Metabolizable Energy
The proportion of digestible energy retained by the body; the remainder is unmetabolizable energy lost in excretory products.
Metabolon
A group of enzymes that are spatially localized within the cell and perform a function together.
Metabotropic Receptor
see also ionotropic receptor
A receptor that signals via a signal transduction pathway.
Metalloprotein
A protein with a metal ion integrated into its structure; enzymatic metalloproteins typically involve their metal in oxidation-reduction reactions.
Metamer
In developmental biology, this refers to a body segment.
Metamorphosis
The transition between distinct developmental stages, typically from a larva to an adult.
Metazoan
A multicellular animal.
Methemoglobin
An oxidized form of hemoglobin that can no longer carry oxygen.