Terminology Flashcards
Define Physiology
the study of normal function, control and integration of various body systems
Define Anatomy.
the study of the normal body organs and structures
Define A band
One of the dark bands that alternate with light (I) bands to create a striated appearance in skeletal or cardiac muscle fibers when these fibers are viewed with a light microscope
Define abomasum
The fourth compartment of the ruminant stomach, which has functions similar to the glandular stomach of non-ruminants
Define absorptive state
The metabolic state following a meal when nutrients are being absorbed and stored; fed state
Define accessory digestive organs
Exocrine organs outside the wall of the digestive tract that empty their secretions through ducts into the digestive tract lumen
Define accessory sex glands
Glands that empty their secretions into the reproductive tract
Define acclimation
A laboratory phenomenon in which the chronic response of an animal to a change in environment is measured; normally the old and new environments differ in one or two highly specific ways
Define acclimatization
The (usually slow) process of changing physiological processes to function more optimally under new conditions
Define accommodation in relation to the eye
In the eye, the ability to adjust the strength of the lens so that both near and far sources can be focused on the retina
Define acetylcholine (ACh)
The neurotransmitter released from all autonomic
preganglionic fibers, parasympathetic postganglionic fibers, and motor neurons
Define acetylcholinesterase (AChE)
An enzyme present in the motor end-plate membrane of a skeletal muscle fiber that inactivates acetylcholine
Define achalasia
A condition that occurs commonly in dogs (and in humans) in which the lower esophageal sphincter fails to relax during swallowing but instead contracts more vigorously
Define acid
A hydrogen-containing substance that on dissociation yields a free hydrogen ion
Define acidosis
Blood pH below the normal range (<7.35 in most mammals)
Define acini
The secretory component of saclike exocrine glands, such as enzyme-producing pancreatic glands or milk-producing mammary glands
Define acquired immune responses
Responses (also called adaptive) that are selectively targeted against particular foreign material to which the body has previously been exposed; see also antibody-mediated immunity and cell-mediated immunity
Define acrorhagia
Special stinging “battle” tentacles in some Anthozoan Cnidarians (anemones, corals)
Define actin
The contractile protein that forms the backbone of the thin filaments in muscle fibers; also contributes to the motility of other kinds of cells
Define active expiration
Emptying of the lungs more completely than when at rest by contracting the expiratory muscles; also called forced expiration
Define active reabsorption
The condition when any step in the transepithelial transport of a substance requires energy expenditure
Define active transport
Active carrier-mediated transport involving transport of a substance against its concentration gradient across the plasma membrane
Define acuity
Discriminative ability; the ability to discern two different points of stimulation
Define adaptation
(1) A reduction in receptor potential despite sustained stimulation of the same magnitude; (2) any feature of an organism that enhances evolutionary fitness
Define adenosine diphosphate (ADP)
The two phosphate products formed from the splitting of ATP to yield energy for the cell’s use
Define adenosine triphosphate (ATP)
The common energy “currency” of all life, which consists of an adenosine with three phosphate groups attached; splitting of the high-energy, terminal phosphate bond provides energy to power cell activities
Define adenylyl cyclase
The membrane-bound enzyme that is activated by a G-protein intermediary in response to binding of
an extracellular messenger with a surface membrane receptor and that, in turn, activates cyclic AMP, an intracellular second messenger
Define adequate stimulus
The main type of stimulus to which a particular receptor (sensory cell) is specialized to respond
Define adiponectin
A hormone produced by adipose tissue in non-obese mammals; may serve in regulating energy balance
Define adipose tissue
The tissue specialized for storage of triglyceride fat; found under the skin in the hypodermis
Define adrenal cortex
The outer portion of the vertebrate adrenal gland; secretes three classes of steroid hormones: glucocorticoids, mineralocorticoids, and sex hormones
Define adrenal medulla
The inner portion of the vertebrate adrenal gland; an endocrine gland that is a modified sympathetic ganglion that secretes the hormones epinephrine and norepinephrine into the blood in response to sympathetic stimulation
Define adrenergic fibers
Nerve fibers that release norepinephrine as their
neurotransmitter
Define adrenocorticotropic hormone (ACTH)
An anterior pituitary hormone that stimulates cortisol secretion by the adrenal cortex and promotes growth of the adrenal cortex
Define aerobes
Organisms that rely on oxygen-based metabolism
Define aerobic
Referring to a condition in which oxygen is available; aerobic metabolism is the process in which ATP formation is accomplished through oxidative phosphorylation
Define afferent arteriole
The vessel that carries blood into the glomerulus of the mammalian kidney’s nephron
Define afferent division
The portion of the peripheral nervous system that carries information from the periphery to the central nervous system; made of afferent neurons, which have sensory receptors at their peripheral endings
Define after hyperpolarization
A slight, transient hyperpolarization that sometimes occurs at the end of an action potential
Define agonist
A nonnative signal molecule (e.g., a drug or toxin) that mimics the effects of a native signal molecule (for opposing term, see antagonist)
Define agranulocytes
Leukocytes that do not contain granules, including lymphocytes and monocytes
Define air capillary
Small airways that branch off from the principal respiratory tubules, the parabronchi, within the avian lung; these are the site of gas exchange between the air and blood
Define air sac
A thin-walled, air-filled component of the avian respiratory system with little musculature and few blood vessels
Define albumin
The smallest and most abundant of the plasma proteins; binds and transports many water-insoluble substances in the blood; contributes extensively to plasma-colloid osmotic pressure
Define aldosterone
The adrenocortical hormone that stimulates
Na + reabsorption by the distal and collecting tu-
bules of the kidney’s nephron during urine
formation
Define alkalosis
Blood pH above the normal range (>7.45 in most mammals)
Define all-or-none law
An excitable membrane either responds to a stimulus with a maximal action potential that spreads nondecrementally throughout the membrane or does not respond with an action potential at all
Define allosteric
A noncatalytic binding site on an enzyme that binds regulatory molecules
Define alpha cells
The endocrine pancreatic islet cells that secrete the hormone glucagon
Define alpha motor neuron
A motor neuron that innervates ordinary skeletal muscle fibers
Define altricial
Referring to young that are absolutely dependent on continued parental care
Define alveolar surface tension
The surface tension of the fluid lining the alveoli in the lungs; see surface tension
Define alveolar ventilation
Volume of air exchanged between the atmosphere and alveoli per minute; equals (tidal volume − dead-space volume) × respiratory rate
Define alveoli in terms of lungs
The air sacs across which O2 and CO2 are exchanged between the blood and air in mammalian (and some other vertebrate) lungs
Define amines
Hormones derived from amino acids, especially tyrosine; include thyroid hormone and catecholamines
Define ammonotelic
Having ammonia as a primary nitrogenous waste product
Define amoebocyte
Wandering immune cell in nonvertebrates
Define amoeboid movement
“Crawling” movement of white blood cells, similar to the means by which amoebas move
Define ampullary electroreceptors
Found in almost all nonteleost fishes and in some teleosts as well as in several amphibian species; respond to low-frequency electric signals that are typical of electrical output from animal nerves and hearts
Define amygdala
Structure of mammalian forebrain (limbic system) located on the interior underside of the temporal lobe; believed to be the homologue of the reptilian and avian paleostriatum; appears to store memories of highly emotional events
Define anabolism
The buildup, or synthesis, of larger organic molecules from the small organic molecular subunits
Define anaerobes
Organisms that can survive on metabolism that does not require oxygen
Define anaerobic
Referring to a condition in which oxygen is not present; in anaerobic metabolism, ATP formation is accomplished by anaerobic glycolysis, usually only for brief periods of time when O2 delivery is inadequate to support oxidative phosphorylation
Define analgesic
Pain relieving
Define androgen
A vertebrate masculinizing “male” sex hormone; includes testosterone from the testes and dehydroepiandrosterone from the adrenal cortex
Define anemia
A reduction below normal in the O2-carrying capacity of the blood
Define anestrus
Condition where a female mammal does not cycle into reproductive readiness, because of insufficient hormonal stimuli
Define angiotensin-converting enzyme (ACE)
An enzyme in the lung that converts inactive angiotensin I to angiotensin II
Define anhydrobiotic
Literally, life without water; referring to dormant stages of organisms with very little water content
Define anion
Negatively charged ion that has gained one or more electrons in its outer shell
Define anoxia
The complete lack of oxygen
Define antagonism in terms of hormones
A process opposing another; e.g., when one hormone causes the loss of another hormone’s receptors, reducing the effectiveness of the second hormone
Define antagonist in terms of signal molecules and muscles
A process opposing another; e.g., (1) a nonnative signal molecule (such as a drug or toxin) blocking the effects of a native signal molecule (for opposite term, see agonist); (2) a muscle that moves in opposition to another
Define anterior pituitary
The nonneural endocrine portion of the vertebrate pituitary gland, having three parts with variable representation in various species: pars tuberalis, pars intermedia, and pars distalis; stores and secretes six different hormones: GH, TSH, ACTH, FSH, LH, and prolactin
Define antibody
A vertebrate immunoglobulin produced by a specific activated B lymphocyte (plasma cell) against a particular antigen; binds with the specific antigen against which it is produced and promotes the antigenic invader’s destruction by augmenting nonspecific immune responses already initiated against the antigen
Define antibody-mediated immunity
A specific immune response accomplished by antibody production by B cells
Define antidiuresis
A state of low urine output
Define antidiuretic hormone
vasopressin
Define antigen
A large complex molecule that triggers a specific immune response against itself when it gains entry into a vertebrate body
Define antigen-presenting cell (APC)
A vertebrate immune cell that can ingest and digest antigens, then “present” them to helper T cells to activate the acquired immune response
Define antimicrobial peptides
Small defensive proteins produced by barrier tissues and some immune cells in many, if not all animals; many kill microbes by creating pores in their membranes
Define antioxidant
A substance that helps inactivate biologically damaging free radicals
Define antiporter
A transporter protein in a membrane that moves two (or more) molecules or ions in the opposite direction
Define antrum (of ovary)
The fluid-filled cavity formed within a developing ovarian follicle
Define antrum (of stomach)
The lower portion of the vertebrate stomach
Define aorta
The large vessel that carries blood from the vertebrate heart to the body
Define aortic valve
A one-way valve that permits the flow of blood from the mammalian left ventricle into the aorta during ventricular emptying but prevents the backflow of blood from the aorta into the left ventricle during ventricular relaxation
Define apnea
T he absence of breathing
Define apodemes
In arthropods, ridges that project from the inner face of the exoskeleton for the attachment of muscles
Define apoptosis
Programmed cell death; deliberate self-destruction of a cell (as opposed to necrosis, unintended cell death)
Define appetite centers
Neuronal clusters in the lateral regions of the vertebrate hypothalamus that drive the animal to eat
Define aquaporin
A protein that forms a channel in a membrane that allows water to diffuse through it
Define aqueous humor
The clear watery fluid in the anterior chamber of the vertebrate eye; provides nourishment for the cornea and lens
Define archaea
Ancient prokaryotes forming one of three distinct forms of life (along with bacteria and eukarya), often found in extreme habitats such as hot springs, salt brines; thought to be related to the ancestor of the main eukaryotic cell
Define aromatase
The enzyme that converts androgens (e.g., testosterone) into estrogens (estradiol)
Define arterioles
The highly muscular, high-resistance vessels of vertebrates, the caliber of which can be changed subject to control to determine how much of the cardiac output is distributed to each of the various tissues
Define artery
A vessel that carries blood away from the heart
Define ascending tract
A bundle of nerve fibers of similar function that travels up the vertebrate spinal cord to transmit signals derived from afferent input to the brain
Define astrocyte
A type of glial cell in the vertebrate brain; major functions include holding the neurons together in proper spatial relationship and inducing the brain capillaries to form tight junctions important in the blood–brain barrier
Define asynchronous
Out of step or phase control of flight muscles; a single Ca2 + release “turns on” the flight muscle; when in this state, the muscle becomes activated by stretch and deactivated by shortening
Define atherosclerosis
A progressive, degenerative arterial disease that leads to gradual blockage of vertebrate vessels, reducing blood flow through them
Define atmospheric pressure
The pressure exerted by the weight of the air in the atmosphere on objects on Earth’s surface; equals 760 mm Hg at sea level
Define ATPase
An enzyme that hydrolyses ATP into ADP and energy
Define ATP synthase
The enzyme within the mitochondrial inner membrane that phosphorylates ADP to ATP
Define atrial natriuretic peptide (ANP)
A peptide hormone released from the vertebrate cardiac atria that promotes urinary loss of Na + in mammals
Define atrioventricular (AV) node
A small bundle of specialized cardiac cells located at the junction of the atria and ventricles that serves as the only site of electrical contact between the atria and ventricles in vertebrates
Define atrioventricular (AV) valve
A one-way valve that permits the flow of blood from the atrium to the ventricle during filling of the mammalian heart but prevents the backflow of blood from the ventricle to the atrium during emptying of the heart
Define atrium
A chamber of the heart that receives blood from the veins or hemolymph and transfers it to a ventricle
Define atrophy
Decrease in mass of an organ by loss of cells
Define autocrine
A locally acting signal molecule regulating a cellular process of the cell that secreted it (“self-stimulation”)
Define autoimmune disease
Disease characterized by erroneous production of antibodies against one of the body’s own tissues
Define autonomic nervous system
The portion of the efferent division of the vertebrate peripheral nervous system that innervates smooth and cardiac muscle and exocrine glands; composed of two subdivisions, the sympathetic nervous system and the parasympathetic nervous system
Define autorhythmicity
The ability of an excitable cell to rhythmically initiate its own action potentials
Define avoiders
Organisms that reduce disturbances to a particular physiological state by behaviorally avoiding environmental changes
Define axon
A single, elongated tubular extension of a neuron that conducts action potentials away from the cell body; also known as a nerve fiber
Define axon hillock
T he first portion of a neuronal axon plus the region of the cell body from which the axon leaves; the site of action potential initiation in most neurons
Define axon terminals
T he branched endings of a neuronal axon, which release a neurotransmitter that influences target cells in close association with the axon terminals
Define B lymphocytes (B cells)
Vertebrate white blood cells that produce antibodies against specific antigens to which they have been exposed
Define bacteria
Prokaryotes forming one of three distinct forms of life (along with archaea and eukarya); included are those related to the ancestors of the eukaryotic mitochondria and chloroplast
Define baculum
Penis bone in some mammals
Define bag cells
Two clusters of cells in crustacean connective tissue above the abdominal ganglion; produce egg-laying hormone (ELH)
Define baleen
Parallel fused filaments of keratin, the same protein of hair fibers that hang from the upper jaws of baleen whales in place of teeth
Define baroreceptor reflex
An autonomically mediated reflex response that influences the vertebrate heart and blood vessels to oppose a change in mean arterial blood pressure
Define baroreceptors
Receptors located within the vertebrate circulatory system that monitor blood pressure
Define basal metabolic rate (BMR)
The minimal rate of internal energy expenditure; an endotherm body’s “idling speed”
Define basal nuclei
Several masses of gray matter located deep within the white matter of the cerebrum of the vertebrate brain; play an important inhibitory role in motor control
Define basal transcription complex
An assembly of proteins that initiate gene transcription in eukaryotes
Define base
A substance that can combine with a free hydrogen ion and remove it from solution
Define basic electrical rhythm (BER)
Self-induced electrical activity of the digestive tract smooth muscle
Define basilar membrane
The membrane that forms the floor of the middle compartment of the vertebrate cochlea and bears the organ of Corti, the sense organ for hearing
Define basophils
White blood cells of vertebrates that synthesize, store, and release histamine, which is important in allergic responses
Define beta cells
The endocrine pancreatic cells that secrete the hormone insulin
Define bicarbonate (HCO3-)
The anion resulting from dissociation of carbonic acid, H 2CO3
Define bile salts
Cholesterol derivatives secreted in vertebrate bile that facilitate fat digestion through their detergent action and facilitate fat absorption through their micellar formation
Define billary system
The bile-producing system, consisting of the liver, gallbladder, and associated ducts in vertebrates
Define bilirubin
A bile pigment antoxidant and waste product derived from biliverdin
Define biliverdin
A bile pigment that is a waste product derived from the degradation of hemoglobin during the breakdown of old red blood cells
Define bimodal
Having two respiratory exchange surfaces, including the gills and either cutaneous exchange or lungs
Define blastocyst
T he developmental stage of the fertilized mammalian ovum by the time it is ready to implant; consists of a single-layered sphere of cells encircling a fluid-filled cavity
Define blood-brain barrier
Special structural and functional features of vertebrate brain capillaries that limit access of materials from the blood into the brain tissue
Define body system
A collection of organs that perform related functions and interact to accomplish a common activity that is essential for survival of the whole body; for example, the digestive system
Define bone marrow
T he soft, highly cellular tissue that fills the internal cavities of vertebrate bones and is the source of most blood cells in terrestrial vertebrates
Define book lung
Respiratory organ in many arachnids consisting of numerous membranous folds arranged like the pages of a book with sheetlike air spaces
Define Bowman’s capsule
The beginning of the tubular component of the mammalian kidney’s nephron that cups around the glomerulus and collects the glomerular filtrate as it is formed
Define Boyle’s law
At any constant temperature, the pressure exerted by a gas varies inversely with the volume of the gas
Define brain
T he most anterior, most highly developed portion of a central nervous system
Define brainstem
T he portion of the vertebrate brain that is continuous with the spinal cord, serves as an integrating link between the spinal cord and higher brain levels, and controls many life-sustaining processes, such as breathing, circulation, and digestion
Define bronchioles
The small branching airways within vertebrate lungs
Define bronchoconstriction
Narrowing of the respiratory airways
Define bronchodilation
Widening of the respiratory airways
Define brush border
The collection of microvilli projecting from the luminal border of epithelial cells lining the digestive tract and kidney tubules
Define buffer system
A mixture in a solution of two or more chemical compounds that minimize pH changes when either an acid or a base is added to or removed from the solution
Define bulbourethral glands
Male accessory sex glands that secrete mucus for
lubrication (in mammals)
Define bulk flow
Movement in bulk of a protein-free plasma across the capillary walls between the blood and surrounding interstitial fluid; encompasses ultrafiltration and re-absorption
Define bulk transport
Active movement of the medium (gas or liquid)
Define bundle of His
A tract of specialized cardiac cells that rapidly transmits an action potential down the interventricular septum of the avian and mammalian heart
Define bursa of Fabricius
A gut-related lymphoid tissue unique to birds; site of B-cell maturation
Define C cells
The thyroid cells that secrete calcitonin
Define calcitonin
A vertebrate hormone secreted by the thyroid C cells that lowers plasma Ca2 + levels
Define calcium homeostasis
Maintenance of a constant free plasma Ca2 + concentration
Define calmodulin
An intracellular Ca2 +-binding protein that, on activation by Ca2 +, induces a change in structure and function of another intracellular protein; especially important in smooth muscle excitation–contraction coupling
Define capacitance
The ability of an insulating material, such as the cell membrane, to store an electrical charge
Define capacitation
The stage in which mammalian spermatozoa become capable of fertilization
Define capillaries
The thin-walled, pore-lined, smallest blood vessels, across which exchange between the blood and surrounding tissues takes place
Define capsaicin
The “hot”-tasting chemical of chili peppers
Define carbonic anhydrase
The enzyme that catalyzes the conversion of CO2 and OH − into HCO3 −
Define cardiac cycle
One period of systole and diastole
Define cardiac muscle
The specialized muscle found only in the heart
Define cardiac output (C.O.)
The volume of blood pumped by each ventricle each minute; equals stroke volume × heart rate
Define cardiovascular control center
The integrating center located in the medulla of the vertebrate brainstem that controls mean arterial blood pressure
Define carnivore
Animal that captures and consumes live prey or that locates and consumes carrion
Define carrier molecules
Membrane proteins that, by undergoing reversible changes in shape so that specific binding sites are alternately exposed at either side of the membrane, can bind with and transfer particular substances unable to cross the plasma membrane on their own
Define carrier-mediated transport
Transport of a substance across the plasma membrane facilitated by a carrier molecule
Define cascade
A series of sequential reactions that culminates in a final product, such as a clot
Define catabolism
The breakdown, or degradation, of large energy-rich molecules within cells
Define catalase
An antioxidant enzyme found in peroxisomes that decomposes potent hydrogen peroxide into harmless H2O and O2
Define catch state
In some nonvertebrates such as bivalve mollusks, a state of continuous contraction of smooth muscle that maintains tension with little metabolic cost
Define catecholamines
The chemical classification of the vertebrates adrenomedullary hormones
Define cations
Positively charged ions that have lost one or more electrons from their outer shell
Define caveolae
Cavelike indentations in the outer surface of the plasma membrane that contain an abundance of membrane receptors and serve as important sites for signal transduction
Define cDNA
DNA code that is synthesized in the laboratory as a complementary copy of an RNA isolated from a tissue
Define cell
The smallest unit capable of carrying out the processes associated with life; the basic unit of both structure and function of living organisms
Define cell adhesion molecules (CAMs)
Proteins that protrude from the surface of the plasma membrane and form loops or other appendages that the cells use to grip each other and the surrounding connective tissue fibers
Define cell body
The portion of a neuron that houses the nucleus and organelles
Define cell-mediated immunity
A specific immune response accomplished by activated T lymphocytes, which directly attack unwanted cells
Define center
A functional collection of cell bodies within the central nervous system
Define central chemoreceptors
Receptors located in the vertebrate medulla near
the respiratory center that respond to changes in
ECF H + concentration resulting from changes in
arterial PC O2 and adjust respiration accordingly
Define central lacteal
The initial lymphatic vessel that supplies each of the vertebrate small intestinal villi
Define central nervous system (CNS)
The brain and longitudinal nerve cord(s), which integrate input from sensory neurons and output to effectors
Define central sulcus
A deep infolding of the mammalian brain surface that runs roughly down the middle of the lateral surface of each cerebral hemisphere and separates the parietal and frontal lobes
Define centrioles
A pair of short, cylindrical structures within a cell that form the mitotic spindle during cell division
Define cerebellum
The portion of the vertebrate brain attached to the brainstem and concerned with maintaining proper position of the body in space and subconscious coordination of motor activity
Define cerebral cortex
The outer shell of gray matter in the vertebrate cerebrum; site of initiation of all voluntary motor output and final perceptual processing of all sensory input as well as integration of most higher neural activity
Define cerebral hemispheres
The cerebrum’s two halves, which are connected by a thick band of neuronal axons
Define cerebrospinal fluid (CSF)
A special cushioning fluid that is produced by, surrounds, and flows through the central nervous system of vertebrates
Define cerebrum
The division of the vertebrate brain that consists of the basal nuclei and cerebral cortex
Define channel
Small water-filled passageway through the plasma membrane; formed by membrane proteins that span the membrane and provide a highly selective passage for small water-soluble substances such as ions
Define chemically gated
Referring to channels in the plasma membrane that open or close in response to the binding of a specific chemical messenger with a membrane receptor site that is in close association with the channel
Define chemoreceptor
A sensory receptor sensitive to specific chemicals
Define chemotaxin
A chemical released at an inflammatory site that attracts phagocytes to the area
Define chemotaxis
Movement of an organism toward or away from a chemical substance
Define chief cells
The vertebrate stomach cells that secrete pepsinogen
Define chitin
A polymer of repeating N-acetylglucosamine, serving as the primary structural molecule of arthropod exoskeletons
Define chloride cells
Specialized cells, which transport NaCl, in the gill epithelia of fishes
Define cholecystokinin (CCK)
A hormone released from the vertebrate duodenal
mucosa primarily in response to the presence of
fat; inhibits gastric motility and secretion, stimulates pancreatic enzyme secretion, and stimulates gallbladder contraction
Define cholesterol
A type of lipid molecule that serves as a precursor for steroid hormones and bile salts and is a stabilizing component of the plasma membrane
Define cholinergic fibers
Nerve fibers that release acetylcholine as their
neurotransmitter
Define chorionic gonadotropin (CG)
A hormone secreted by the early mammalian embryo and developing placenta that stimulates and maintains the corpus luteum of pregnancy
Define chromatophores
Pigment-containing cells that are found in the integument of some animals and are responsible for physiological color change; the color granules are dispersed or concentrated depending on the animal’s perception of its surroundings
Define chronic obstructive pulmonary disease
A group of lung diseases characterized by increased airway resistance resulting from narrowing of the lumen of the lower airways; includes asthma, chronic bronchitis, and emphysema
Define chyme
A thick liquid mixture of food and digestive juices
Define cilia
Motile hairlike protrusions from the surface of many cells, such as in ciliate protozoa, flatworm integument, and linings of mammalian respiratory airways and oviducts
Define ciliary body
The portion of the vertebrate eye that produces aqueous humor and contains the ciliary muscle
Define ciliary muscle
A circular ring of smooth muscle, within the vertebrate eye, whose contraction increases the strength of the lens to accommodate for near vision
Define circadian rhythm
Repetitive oscillations in the set point of various body activities, such as hormone levels and body temperature, that are very regular and have an approximate frequency of 24 hours, usually linked
to light–dark cycles; diurnal rhythm; biological
rhythm
Define circannual
biological rhythm that fluctuates yearly
Define cistern
Structure associated with the mammalian teat; permits pooling of milk from several ducts before exiting the gland
Define citric acid cycle (Krebs cycle)
A cyclical series of biochemical reactions that involves the further processing of intermediate breakdown products of nutrient molecules, resulting in the generation of carbon dioxide and the preparation of hydrogen carrier molecules for entry into the high-energy–yielding electron transport chain
Define cloaca
The final chamber of the hindgut of birds and reptiles
Define clone
An exact genetic copy of a gene, or an organism arising from an exact copy of a genome
Define clutch
The number of eggs incubated at one time
Define cochlea
The snail-shaped portion of the vertebrate inner ear that houses the receptors for sound
Define coevolution
The process in which adaptive changes in one organism favor selection for adaptations in a second organism, which, in turn, favor selection for a different adaptation in the first organism, and so on
Define collecting tubule
The last portion of tubule in the mammalian kidney’s nephron that empties into the renal pelvis
Define colligative properties
Solution properties of an idealized solute at 1 mole in 1 kg of water (defined as 1 molal), which has an osmotic pressure of 22.4 atmospheres (atm), raises boiling point by 0.54°C, depresses freezing point by 1.86°C, and also reduces vapor pressure
Define colloid
The thyroglobulin-containing substance enclosed within the thyroid follicles
Define colloid osmotic pressure
T he difference in osmotic pressure that exists between the ECF and ICF due to differences in their concentrations of nonpermeating proteins
Define compatible osmolyte
An organic osmolyte that elevates the osmotic pressure of a body fluid without perturbing cell functions
Define complement system
A collection of vertebrate plasma proteins that are activated in cascade fashion on exposure to invading microorganisms, ultimately producing a membrane attack complex that destroys the invaders
Define compliance
The distensibility of a hollow, elastic structure, such as a blood vessel or the lungs; a measure of how easily the structure can be stretched
Define compound eye
Multifaceted arthropod eye composed of umerous optical units called ommatidia
Define concentration gradient
A difference in concentration of a particular substance between two adjacent areas
Define conduction
Transfer of heat between objects of differing temperatures that are in direct contact with each other
Define cones in terms of the eye
The vertebrate eye’s photoreceptors used for color vision in the light
Define conformers
Organisms in which a particular physiological state matches that of the environment
Define congestive heart failure
The inability of the cardiac output to keep pace with the body’s needs for blood delivery, with blood damming up in the veins behind the failing heart
Define connective tissue
Tissue that serves to connect, support, and anchor various body parts; distinguished by relatively few cells dispersed within an abundance of extracellular material.
Define contiguous conduction
The means by which an action potential is propagated throughout a non-myelinated nerve fiber; local current flow between an active and adjacent inactive area brings the inactive area to threshold, triggering an action potential in a previously inactive area
Define contractile proteins
Myosin and actin, whose interaction brings about shortening (contraction) of a muscle fiber
Define conus arteriosus
In cartilaginous fish, a chambered extension of the ventricle through which blood exits the heart
Define convection
Transfer of heat energy by air or water currents
Define convergence
(1) The converging of many presynaptic terminals from thousands of other neurons on a single neuronal cell body and its dendrites so that activity in the single neuron is influenced by the activity from many other neurons; (2) the independent evolution of similar structures in different species without a common ancestral structure
Define convex
Curved out, as a surface in a lens that converges light rays
Define cooperativity
The binding of a ligand, such as O2, to its binding site on a multisubunit protein, such as hemoglobin, subsequently affecting the ability of other binding sites on the same protein to associate with additional ligand
Define coprodaeum
Anterior portion of the avian cloaca, receives the excreta from the digestive tract
Define coprophagy
Reingestion of feces
Define copulatory plug
Temporary mating plug that forms after fertilization, which prevents both the loss of semen from the female tract as well as entry of sperm into the vagina (genital chamber) from a competing male
Define core temperature
The temperature within the inner core of a body (abdominal and thoracic organs, central nervous system, and skeletal muscles)
Define cornea
The clear, most anterior,
outer layer of an eye, through which light rays
pass to the interior of the eye
Define corpus luteum
The ovarian structure that develops from a ruptured follicle following ovulation in a mammal
Define cortisol
The vertebrate adrenocortical hormone that plays an important role in carbohydrate, protein, and fat metabolism and helps the body resist stress; functionally similar to corticosterone
Define counteracting osmolyte
An organic osmolyte that elevates the osmotic pressure of a body fluid and that counteracts the effects of a perturbant of cellular macromolecules
Define countercurrent
A design in which fluid in two juxtaposed tubes flows in opposite directions (alternatively, in which flow in a single tube alternates between inflow and outflow)
Define cranial nerves
The 12 pairs of vertebrate peripheral nerves, the majority of which arise from the brainstem
Define crop
An enlarged posterior portion of the foregut, just anterior to the esophagus
Define crop milk
Lipid material synthesized by epithelial cells of the crop of adult pigeons and doves; these cells are sloughed off and mixed with food already present in the crop and fed by regurgitation to juveniles
Define cross bridges
T he myosin molecules’ globular heads that protrude from a thick filament within a muscle fiber and interact with the actin molecules in the thin filaments to shorten the muscle fiber during contraction
Define crosscurrent exchange
Airflow and blood flow in the parabronchi of the avian lung that occur perpendicular to one another
Define cryoprotectant
A molecule that is used to prevent freezing by lowering the freezing point in a
body fluid
Define cyclic adenosine monophosphate (cyclic AMP or cAMP)
An intracellular second messenger derived from adenosine triphosphate (ATP)
