Chapter 44 - Controlling The Internal Environment

Front 1

Thermoregulation

Back 1

the maintenance of body temperature within a range that enables cells to function efficiently

Front 2

Conduction

Back 2

the direct transfer of thermal motion from an object of warmer temperature to an object of cooler temperature, or between molecules of the body and those of the environment

Front 3

Convection

Back 3

the transfer of heat by the movement of air or liquid past the surface of a body

Front 4

Radiation

Back 4

the emission of electromagnetic waves produced by all objects warmer than absolute zero; transfer heat between objects that are not in direct contact

Front 5

Evaporation

Back 5

the loss of heat from the surface of a liquid that is loosing some of its molecules as gas; evaporation of water has a significant cooling effect on animals

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Ectotherm

Back 6

a classification of animals; warms their bodies by absorbing heat from the surroundings

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Endotherm

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a classification of animals; derives most or all of its heat from its own metabolism; most maintain relatively constant temperature despite wide fluctuation in external temperature; energetically expensive

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Vasodilation

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an increase in the diameter of superficial blood vessels; nerves signal the vessels to relax allowing more blood flow; allows more heat to be transferred to the environment

Front 9

Vasoconstriction

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reduces blood flow and heat loss by decreasing the diameter of superficial vessels; prompted by neural signaling; restricts heat transfer to the external environment; thermoregulatory technique

Front 10

Counter-current heat exchange

Back 10

important mechanism for controlling heat loss in many endothermic animals; allows heat transfer to occur from the warmer arteries to the cooler veins; especially prominent in marine endotherms

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Nonshivering thermogenesis

Back 11

hormonal triggering of heat production; hormones trigger metabolic heat production rather than that of ATP

Front 12

Brown fat

Back 12

a tissue found in the neck of some animals that is specialized for rapid heat production; sight of nonshivering thermogenesis in some animals

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Acclimatization

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a physiological response of an animal that allows it to adjust to a new range of environmental temperatures over a period of days or weeks; i.e. seasonal change; may involve changes in internal thermostat settings and may involve cellular adjustments

Front 14

Stress-induced proteins

Back 14

special protein molecules produced by cells in laboratory cultures when subjected to extreme stressors such as temperature change, rapid pH change, or toxin exposure

Front 15

Heat shock proteins

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a type of stress-induced protein synthesized by cultured cells that are subject to rapid and extreme heat change; help maintain the integrity of other proteins that would be denatured by severe heat

Front 16

Torpor

Back 16

an alternative physiological state in which metabolism decreases and the heart and respiratory system slow down; essentially, body’s thermostat gets turned down

Front 17

Hibernation

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long-term torpor in which the body temperature is lowered as an adaptation to winter cold and food scarcity

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Estivation

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summer torpor is characterized by slow metabolism and inactivity

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Osmoregulation

Back 19

how an organism regulates solute balance and the gain or loss of water

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Transport epithelium

Back 20

a layer or layers of specialized epithelial cells that regulate solute movements; in most animals, transport epithelia are arranged into tubular networks with extensive surface area; molecular structure of plasma membrane determines the kinds of solutes that move across transport epithelia and the direction they move

Front 21

Ammonia

Back 21

toxic byproduct of metabolism; most aquatic animals secrete ammonia directly because it dissolves easily in water; in fishes it is usually lost as ammonium ion through the gills; unsuitable for waste excretion on land

Front 22

Urea

Back 22

100,000x less toxic than ammonia; produced in the vertebrate liver by a metabolic cycle that combines ammonia with carbon dioxide; carried to the excretory organs (kidneys) by the circulatory system; by secreted high concentrations of urea, an animal can conserve water

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Uric acid

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can be excreted in a pastelike form with very little loss of water; thousands of times less soluble in water than either ammonia or urea; excreted by birds, reptiles, land snails, etc.

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Osmolarity

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total solute concentration expressed as molarity; often expressed in milliosmoles per liter; isoosmotic refers to two solutions of the same relative osmolarity; hypoosmotic refers to the more dilute solution, hyperosmotic refers to more concentrated solutions

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Osmoconformer

Back 25

an animal that does not adjust its internal osmolarity because its internal fluids are isoosmotic with the external environment

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Osmoregulator

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animal that must regulate its internal osmolarity; because its internal fluid or solute is not isoosmotic to the external environment, it must be changed to regulate loss; an energetically costly process

Front 27

Stenohaline

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animals that cannot tolerate wide fluctuations in the osmolarity of their body fluids

Front 28

Euryhaline

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animals that can survive wide fluctuations in the osmolarity of their internal body fluids

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Anhydrobiosis

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the ability of some aquatic invertebrates living in temporary ponds to lose all their water and survive in a dormant state when their habitat dries up; means “life without water”; cryptobiosis means hidden life; i.e. water bears

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Excretion

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the process by which animals get rid of nitrogenous-containing waste products that are a byproduct of metabolism

Front 31

Filtration

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a process by which blood or other body fluids is exposed to a filtering device made of the selectively permeable membrane

Front 32

Reabsorption

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selective transport of water and valuable solutes, such as glucose, salts, and amino acids, from the filtrate back into the body fluids; important because of the nonselectivity of filtration

Front 33

Secretion

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the process by which solutes are removed from the animal’s body fluid and added to the filtrate

Front 34

Protonephridium

Back 34

a network of closed tubules lacking internal openings; excretory system in animals such as flatworms and other simple animals; incorporates a flame bulb with a tuft of cilia that the beat and provide a force that draws water and solutes from the interstitial fluid through the flame bulb and into the tubule system; functions mainly in osmoregulation

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Metaniphridium

Back 35

a type of tubular excretory system that has internal openings that collect body fluids; exists in most annelids, has osmoregulatory and excretory functions; in earthworms, urine leaves the body through nephridiopores

Front 36

Malpighian tubules

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excretory organs of insects and other terrestrial arthropods; tubules that remove nitrogenous wastes from the hemolymph and also function in osmoregulation

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Ureter

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the duct through which urine leaves the kidney and drain into the urinary bladder

Front 38

Urinary bladder

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holds urine until it is excreted from the body

Front 39

Renal cortex

Back 39

the outer anatomical region of the kidney

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Renal medulla

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inner anatomical region of the kidney

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Nephron

Back 41

the functional unit of the vertebrate kidney; consists of a single long tubule and a ball of capillaries

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Glomerulus

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a ball of capillaries at one end of the nephron

Front 43

Bowman’s capsule

Back 43

a capsule that surrounds the glomerulus

Front 44

Podocytes

Back 44

specialized cells of the Bowman’s capsule that function as a filter; permeable to water and small solutes, but not blood cells or large macromolecules such as proteins

Front 45

Proximal tubule

Back 45

initial region of the nephron tubule

Front 46

Loop of Henle

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a hairpin turn with an ascending limb and a descending limb; major functional region of solute diffusion and water osmosis

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Distal tubule

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final region of the nephron tubule

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Collecting duct

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receives filtrate from many nephrons; empty into the renal pelvis

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Cortical nephrons

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about 80% of the nephron tubules in human kidneys have reduced loops of Henle and are almost entirely confined to the renal cortex

Front 50

Juxtamedullary nephrons

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about 20% of the nephrons in the human kidneys that have well developed loops that extend into the renal medulla

Front 51

Afferent arteriole

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a branch of the renal artery the subdivides into the capillaries of the glomerulus; supply every nephron with blood

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Efferent arteriole

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convergence of capillaries leaving the glomerulus

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Peritubular capillaries

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a second subdivision of capillaries that intermingle with the proximal and distal tubules of the nephron

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Vasa recta

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capillaries that extend down the loop of Henle, also forming a loop

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Antidiuretic hormone (ADH

Back 55

hormone produced in the hypothalamus that is important in osmoregulatory processes; stored and released from the pituitary gland; if blood osmolarity rises about 300 mosm/L, additional ADH is released into the bloodstream

Front 56

Juxtaglomerular apparatus (JGA)

Back 56

a tissue that helps regulate kidney function; located near the afferent arteriole and supplies blood to the glomerulus, when blood pressure or blood volume in the afferent arteriole drops, the enzyme rennin initiates chemical reactions that convert a plasma protein called angiotensinogen to angiotnesin II

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Angiotensin II

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a peptide converted from angiotensinogen by rennin; increases blood pressure and blood volume in several ways, constricts arterioles, stimulates proximal tubules to reabsorb more NaCl and water, and stimulates adrenal glands to release aldosterone

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Aldosterone

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a hormone released by the adrenal glands that acts on the nephrons’ distal tubules making them reabsorb more Na+ and water

Front 59

Rennin-angiotensin-aldosterone system (RAAS)

Back 59

a complex feedback circuit that functions in osmotic homeostasis

Front 60

Atrial natriuretic factor (ANF)

Back 60

a hormone that is opposed to the RAAS; released by the walls of the heart; inhibits the release of renin from JGA, inhibits NaCl absorption by collecting ducts, and reduces aldosterone release from adrenal glands