P Flashcards
P_50
The partial pressure at which a respiratory pigment is 50 percent saturated with oxygen.
Pacemaker
A cell or group of cells whose output of action potentials occurs in a rhythmic pattern.
Pacemaker Cell
An excitable cell that spontaneously fires action potentials in a rhythmic pattern.
Pacemaker Potentials
Spontaneous depolarizations of the resting membrane potential that ultimately trigger action potentials within pacemaker cells.
Pacinian Corpuscle
A type of vertebrate skin mechanoreceptor.
Pancreas
A vertebrate organ that produces endocrine hormones including insulin and glucagon and also produces exocrine secretions that are involved in digestion.
Pancreatic Beta Cells
Cells within the vertebrate pancreas that secrete the hormone insulin.
Panting
A mode of thermoregulation whereby an increase in the frequency of respiration enhances heat loss from the body core.
Papillary Muscles
Muscles connected to the chordae tendineae of the mammalian heart that help to anchor the atrioventricular valves.
Parabronchi
Smallest airways of a bird lung.
Paracellular Pathway
The pathway via which paracellular transport occurs.
Paracellular Transport
Passage of solutes or water between cells; in most epithelial tissues, tight junctions and other cell-cell junctions prevent paracellular movement of fluids.
Paracellular Transport
Passage of solutes or water between cells; in most epithelial tissues, tight junctions and other cell-cell junctions prevent paracellular movement of fluids.
Paracrine
A type of chemical messenger that is involved in local signaling between nearby cells; paracrine messengers move through the interstitial fluid by diffusion.
Parafacial Respiratory Group
A group of neurons in the vertebrate brain that is involved in the generation of respiratory rhythms.
Parallel Evolution
The evolution of a shared underlying trait in similar ways in two distinct but related lineages.
Paralogs
see also homologs, orthologs
Genes that are the result of a gene duplication event within a lineage.
Parasympathetic Nervous System
Part of the vertebrate autonomic nervous system; generally active during periods of rest; releases acetylcholine onto target organs.
Parathyroid Glands
Glands located on the posterior surface of the thyroid gland that release parathyroid hormones in response to changes in extracellular calcium.
Parathyroid Hormone
Peptide hormone that regulates blood calcium levels.
Parietal Cells
The acid-secreting cells within the gastric mucous membrane.
Parthenogenesis
A mode of asexual reproduction whereby offspring are produced by a female as a result of a variation on the meiotic pathway. Because meiosis is involved, chromosomal recombination is possible and the parthenogenic offspring are not clones of the parent.
Partial Pressure
The pressure exerted by one of the gases in a gas mixture. The sum of the partial pressures of all the gases in a mixture gives the total pressure.
Partition Coefficient
A measure of the relative ability of a solute to dissolve in two different solutes, such as oil and water.
Parturition
The birthing process by which offspring of viviparous and ovoviviparous females are expelled from the reproductive tract.
Parvalbumin
A Ca2+-binding protein in the cytoplasm of some muscles, which buffers Ca2+ levels to accelerate relaxation.
Passive Diffusion
A type of passive transport that does not require a protein carrier.
Passive Transport
Movement across a cell membrane without an energy investment other than the chemical gradient of the transported molecule; includes both passive diffusion and facilitated diffusion.
Patch Clamping
A method used by neurobiologists to study the function of ion channels, in which the voltage or current across a small patch of membrane is manipulated using a small glass microelectrode applied to the surface of the cell.
Pathogen-Associated Molecular Patterns (PAMPs)
Molecules arising from pathogens that can be recognized as foreign by immune cells.
Pattern Generator
A group of neurons whose rhythmic firing coordinates a rhythmic physiological process or behavior, such as breathing or locomotion.
Pattern-Recognition Receptors (PRRs)
Proteins produced by the immune system that bind PAMPs.
Pavement Cells
Cells within the gills of fish that are responsible for gas exchange.
Pejus Temperature
The temperatures at which physiological processes start to decline in function when temperature is above or below the optimum for function.
Pentose
A five-carbon monosaccharide, such as ribose and deoxyribose.
Peptide Bond
A carbon-nitrogen bond (–C–N–); most common in polymers of amino acids
Perfusion
Movement of fluid through a tissue (e.g., flow of blood through a capillary bed).
Pericardium
The sac surrounding a heart.
Pericyte Cell
Contractile cells that wrap around capillaries.
Perilymph
The fluid found in the cochlea of the inner ear.
Peripheral Chemoreceptors
Chemoreceptors located in the aortic and carotid bodies of vertebrates that detect changes in blood chemistry.
Peripheral Membrane Protein
A protein that is weakly bound to the membrane through an interaction with a lipid or integral membrane protein.
Peripheral Nervous System (PNS)
All of the neurons outside of the central nervous system.
Peristalsis
The rhythmic contractions of intestinal smooth muscle; involved in propelling a bolus of food along the gastrointestinal tract and in moving blood through the circulatory systems of some animals.
Permeability
The ability of a molecule to cross a barrier, such as a membrane.
Permeability
The ability of a molecule to cross a barrier, such as a membrane.
Permease
A transporter that mediates facilitated diffusion, but is neither a channel nor a porin.
pH Scale
A measure of acidity, expressed as the negative log_10 of the proton concentration.
pH-Bicarbonate Plot (Davenport diagram)
A graphical depiction of the relationship between the pH and bicarbonate concentration of a solution. Usually used to describe these relationships in arterial blood.
Phagocyte
A cell that carries out phagocytosis.
Phagocytosis
The endocytosis of large particles from the extracellular space.
Phagocytosis
The endocytosis of large particles from the extracellular space.
Phasic Muscle
A type of muscle that undergoes rapid contractions and relaxations; a twitch muscle.
Phasic Receptor
A sensory receptor that produces action potentials only during part of the stimulus (usually at stimulus onset and removal).
Phenotype
The physical characteristics of an organism; the result of an interaction between the genotype and the environment.
Phenotypic Plasticity
see also acclimation
Production of different phenotypes by a single genotype as a result of environmental cues; may be reversible or irreversible.
Pheromones
Chemical messengers released by an animal into the environment that have an effect on another animal of the same species.
Phosphagens
Energy-rich compounds that transfer energy in reactions in which a large change in free energy results when a phosphate bond is broken.
Phosphatase
An enzyme that removes a phosphate group from a molecule; important in signal transduction pathways because it reverses the phosphorylations catalyzed by kinases.
Phosphodiester Bond
–P–O–P–.
Phosphodiesterase
An enzyme that breaks down the phosphodiester bonds of cyclic nucleotides such as cAMP and cGMP.
Phosphoglycerides
The major class of phospholipids of biological membranes, consisting of a glycerol backbone, two fatty acids, and a polar head group linked to the glycerol via phosphate.
Phospholipase
An enzyme that breaks down phospholipids, releasing either diacylglycerol, polar head groups, or fatty acids, depending on the type of phospholipase.
Phospholipids
Phosphoglycerides and sphingolipids.
Phosphorylation
The addition of a phosphate group via a kinase, expending ATP (e.g., a protein kinase catalyzes the phosphorylation of a protein).
Phosphorylation Cascade
A type of signal transduction pathway that involves multiple phosphorylation steps.
Phosphorylation Potential
An expression of energy status; the mass action ratio for an ATPase reaction ([ATP]/[ADP][Pi]).
Photon
The fundamental particle of electromagnetic radiation. Streams of photons can have differing wavelengths, in which case the resulting radiation is given different names (e.g., X-rays, gamma rays, visible light).
Photoperiod
The length of the light and dark phases of a day.
Photopigments
Molecules specialized for detecting photons; consist of a chromophore and an associated protein.
Photoreceptors
Sensory receptors that detect photons with wavelengths in the visible spectrum (i.e., light). Can be used to describe either the receptor proteins or the cells that contain them.
Phototaxis
Movement in response to light, either toward (positive phototaxis) or away (negative phototaxis).
Phylogenetic
Pertaining to phylogeny.
Phylogeny
A hypothesis regarding the evolutionary relationships among organisms; can be based on the analysis of various types of data (e.g., molecular, morphological).
Physiological Dead Space
The volume of a respiratory organ that is not involved in gas exchange; consists of both the anatomical dead space and the volume of any regions that, although capable of acting as gas exchange surfaces, do not participate in gas exchange (e.g., unperfused or unventilated alveoli).
Physoclist
Any fish whose swim bladder lacks a connection to the gut.
Physostome
Any fish whose swim bladder is connected to the gut via a tube.
Piloerection
The movement of hair or feathers perpendicular to the skin in response to muscular contraction.
Pilomotor
Related to the nerves and muscles that change the orientation of hair.
Pineal Complex
Consists of the pineal gland and related structures; involved in melatonin secretion and the establishment of circadian rhythms.
Pineal Gland
An endocrine organ located in the brain of vertebrates. In nonmammalian vertebrates it is light sensitive. See pineal complex.
Pinna
The cartilaginous structures forming the outer ear of mammals.
Pinocytosis
see also phagocytosis
The endocytosis of fluids by the plasma membrane.
Pit Organs
The highly sensitive thermoreceptive organs of some snakes.
Pituitary Gland
A hormone-secreting organ located at the base of the vertebrate brain; connected to the hypothalamus.
Pivotal Temperature
In an animal with environmental sex determination, it is a temperature at which equal numbers of males and females result.
Place Coding
Mechanism by which the inner ear detects the pitch (frequency) of a sound. Different areas of the basilar membrane of the inner ear respond to each pitch, converting the frequency information into location (place) information.
Placenta
In eutherian mammals, the membrane derived from the embryonic chorion that encircles the embryo, acting as the interface between embryonic and maternal tissues.
Plane Polarized Light
When light arrives at a detector, it typically exhibits waves that run at all angles. Polarizing filters permit the passage of light waves that run in a specific angle (plane), generating plane-polarized light.
Plasma
The liquid fraction of vertebrate blood.
Plasma Membrane
The lipid bilayer membrane that encircles a cell.
Plasticity
See also phenotypic plasticity
The ability to change or remodel a physiological process or structure, as in neural plasticity.
Plateau Phase
The phase of a cardiac action potential characterized by a sustained depolarization as a result of calcium influx.
Pleiotropy
A phenomenon in which a single gene is responsible for multiple, seemingly independent phenotypes.
Pleural Cavity
The space between the pleural sacs surrounding the lungs of vertebrates. Low pressure in the pleural cavity helps to keep the lungs from collapsing.
Pleural Sacs
A series of membranes that surround the lungs of vertebrates. The pleural sacs enclose the pleural cavity.
Plexus
A complex network of blood vessels or nerves.
Plug-Flow Reactor
A type of chemical reactor in which the inflow moves as a bolus through the tubelike reactor.
pN
The pH at which a zwitterion has no net charge
Podocyte
Cells surrounding the capillaries of the glomerulus, with footlike extensions that form the filtration slits.
Poikilothermy
A thermoregulatory strategy whereby an animal (a poikilotherm) allows body temperature (T_B) to vary, usually in relation to the ambient conditions.
Poiseuille’s Equation
An equation describing the relationship between the flow, pressure, and resistance of a fluid moving through a rigid tube, including the factors influencing resistance (length, cross-sectional area, and viscosity).
Polymer
A chain of repeating molecules, such as a polysaccharide or a polypeptide.
Polymodal Receptors
Sensory receptor cells that can detect more than one type of stimulus.
Polymorphonuclear (PMN) Cells
White blood cells of the immune system that possess multilobed nuclei.
Polypeptide
A chain of amino acids linked by peptide bonds.
Polyphenism
A form of irreversible phenotypic plasticity, generally involving alternative developmental pathways.
Polypnea
Rapid breathing.
Polysaccharide
A chain of monosaccharides linked by glycosidic bonds.
Polysynaptic
Involving more than two synapses; used in the context of reflex pathways.
Polyunsaturated Fatty Acid
A fatty acid with two or more double bonds along the carbon chain.
Pons
A region of the vertebrate brain that communicates information between the brainstem and the higher brain centers. Works with the medulla to regulate breathing.
Population Coding
A phenomenon in which information about a stimulus is encoded in the pattern of firing of multiple neurons.
Porin
A channel that permits the facilitated diffusion of large molecules; e.g., aquaporin is a porin that transports water.
Porphyrins
Organic ring structures that bind metals, primarily iron but also copper; heme is the most common type of porphyrin in animals.
Portal System
Two capillary beds connected by a portal vein (e.g., hypothalamic pituitary portal system; intestinal liver portal system).
Portal Vein
A blood vessel that carries blood from one capillary bed to another; part of a portal system.
Positive Feedback Loop
A regulatory mechanism whereby a step late in a pathway causes an increase in the activity of a step earlier in the pathway to increase the flow through the pathway.
Positive Work
Work performed during muscle shortening.
Posterior Pituitary
Lobe of the pituitary gland; secretes antidiuretic hormone and oxytocin; also called the neurohypophysis.
Postganglionic Neuron
A vertebrate autonomic neuron has its synapse in the peripheral autonomic ganglia, and extends an axon out into the periphery; forms a synapse with a preganglionic neuron.
Postprandial Period
A period of altered metabolism after a meal has been eaten.
Postsynaptic Cell
A cell (either a neuron or effector) that receives a signal from a presynaptic cell across a synapse.
Post-Tetanic Potentiation (PTP)
A phenomenon in which a postsynaptic cell will respond with an unusually large change in membrane potential for several minutes following repeated action potentials in the presynaptic cell.
Potential Energy
The energy that is available in a static system; elastic storage energy is a form of potential energy.
Power
The rate of doing work.
Power-Velocity Curve
The relationship between the velocity of muscle shortening and the force of contraction.
Power Stroke
The part of a cross-bridge cycle in which structural changes in myosin alter the relative position of the actin flilament.
Pre-Bötzinger Complex
The primary respiratory rhythm generator of mammals.
Preformed Water
The water that arrives in the diet as a liquid or trapped within solid foods; distinct from metabolic water that is produced during the digestion of foods.
Preganglionic Neuron
A vertebrate autonomic neuron that has its cell body in the central nervous system and forms synapses in the peripheral ganglia.
Preprohormone
see also prohormone
Large inactive polypeptide that is a precursor to a peptide hormone.
Pressure
A force applied to a unit area of a surface.
Pressure Drag
The resistance that arises as an object moves through a fluid as a result of the interaction with the leading edge of the surface encountering the fluid.
Presynaptic Cell
A neuron that transmits a signal across a synapse to a postsynaptic cell.
Primary Active Transport
Active transport that uses chemical or light energy directly, such as an ion-pumping ATPase; distinct from secondary active transport, in which an entity is driven by electrochemical transmembrane gradients of another entity being transported.
Primary Follicle
A follicle that continues to develop to release an ovum, unlike other follicles that degrade and die during the maturation process (atresia).
Primary Oocyte
The products of oogonia that have undergone the first meiotic division to become a diploid cell that will eventually produce an ovum.
Primary Spermatocyte
The products of spermatagonia that have undergone the first meiotic division to become a diploid cell that will eventually produce a spermatozoan.
Primary Structure
The sequence of a polymer without consideration of how it folds; typically refers to the amino acid sequence of a protein.
Primary Urine
The initial contents of the lumen of a nephron. In vertebrates that possess a glomerulus, the primary urine is the filtrate.
Proboscis
A single extension from the head, typically superior to the oral opening; the nose.
Proenzyme
A catalytically inactive precursor for an enzyme; usually undergoes proteolytic processing to become the active enzyme.
Progenote
The last universal common ancestor of all organisms.
Progesterone
A steroid hormone involved in embryogenesis in all vertebrates; also regulates the menstrual cycle and pregnancy in mammals.
Prohormone
A polypeptide formed by the cleavage of a preprohormone; a precursor to the formation of a peptide hormone.
Prolactin
An anterior pituitary hormone that is responsible for milk production in mammals, and more general roles in ion and water balance in other vertebrates.
Pronephros
A simple kidney equivalent of larval forms of some amphibians and fish.
Proprioceptor
A sensory receptor that provides information about body position and movement.
Prostate Gland
A gland accessory associated with the reproductive tract of male vertebrates.
Prosthetic Group
A nonprotein component of an enzyme or other protein; e.g., a coenzyme (an organic prosthetic group) or a metal.
Protease
An enzyme that breaks peptide bonds of proteins to generate polypeptides or amino acids.
Proteasome
A cytoplasmic multiprotein complex that degrades damaged proteins tagged with a ubiquitin molecule.
Protein
A polymer of amino acids, usually folded into complex secondary structures.
Protein Kinase
An enzyme that attaches a phosphate to a protein, using a molecule of ATP for energy and as a phosphate source.
Protein Phosphatase
An enzyme that removes a phosphate group from a protein.
Proteoglycan
A molecule composed of protein and glycosaminoglycan.
Proteolysis
The breakdown of proteins, usually by hydrolytic cleavage of peptide bonds by a protease.
Prothoracic Glands
A pair of endocrine glands that secrete hormones that regulate ecdysis.
Protist
Any one of a diverse collection of distantly related eukaryotic unicellular microorganisms.
Protofilament
A single chain of tubulin that exists prior to the formation of sheets or microtubules.
Proton Motive Force
The electrochemical gradient arising from proton pumping by the mitochondrial electron transport chain.
Protonephridia
Excretory organs consisting of a tubule-like structure; found in organisms that lack a coelom or vascular system (e.g., platyhelminths).
Protonephridium
A simple kidney tubule-like structure, typically with a flame cell to generate fluid movements.
Protostomes
The group of animals that, during embryogenesis, have a blastopore that becomes the mouth, such as mollusks, annelids, and arthropods.
Protozoans
An historical term to describe the phyla of early single-celled eukaryotes known now as protists.
Proximal Tubule
The region of a mammalian or avian kidney tubule that lies between the Bowman’s capsule and the descending limb of the loop of Henle.
Proximate Cause
see also ultimate cause
The immediate or direct cause of an organismal structure, function, or behavior; usually refers to the developmental or physiological mechanism.
Pulmonary Artery
Blood vessel leading from the heart to the lungs of mammals that carries deoxygenated blood.
Pulmonary Circuit
The part of the tetrapod circulatory system that carries blood from the heart to and from the lungs.
Pulmonary Semilunar Valve
The valve between the right ventricle and the pulmonary artery of the mammalian cardiovascular system.
Pulmonary System
A respiratory system consisting of lungs and the associated vasculature.
Pulmonary Vein
Blood vessel leading from the lungs to the heart of mammals that carries oxygenated blood.
Pupa
A developmental stage in hemimetabolous insects that separates the larva from the adult; can include a period of quiescence.
Pupil
An opening in the center of a cameratype eye through which light enters.
Purine
A class of nitrogenous bases with two rings; includes guanine and adenine.
Purkinje Fibers
The terminal branches of the conducting fibers of the mammalian heart.
P Wave
One of the waveforms of an electrocardiogram; represents the depolarization of the atria.
Pyloric Sphincter
The sphincter that regulates movement of material from the stomach to the duodenum.
Pyrimidine
A class of nitrogenous bases with one ring; includes cytosine, thymine, and uracil.
Pyrogen
An entity that causes a homeotherm to mount an immune response that culminates in a fever.
