chapter 44
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Chapter 44. Osmoregulation and Excretion. Fig. 44-1. Osmoregulation regulates solute concentrations and balances the gain and loss of water. Concept 44.1: Osmoregulation balances the uptake and loss of water and solutes. Cells require a balance between osmotic gain and loss of water - PowerPoint PPT PresentationTRANSCRIPT
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Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
PowerPoint® Lecture Presentations for
Biology Eighth Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp
Chapter 44Chapter 44
Osmoregulation and Excretion
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Fig. 44-1
Osmoregulation regulates solute concentrations and balances the gain and loss of water
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Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Concept 44.1: Osmoregulation balances the uptake and loss of water and solutes
• Cells require a balance between osmotic gain and loss of water
• Osmolarity, the solute concentration of a solution, determines the movement of water across a selectively permeable membrane
• If two solutions are isoosmotic, the movement of water is equal in both directions
• If two solutions differ in osmolarity, the net flow of water is from the hypoosmotic to the hyperosmotic solution
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Fig. 44-2
Selectively permeablemembrane
Net water flow
Hyperosmotic side Hypoosmotic side
Water
Solutes
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Osmotic Challenges
• Osmoconformers, consisting only of some marine animals, are isoosmotic with their surroundings and do not regulate their osmolarity
• Osmoregulators expend energy to control water uptake and loss in a hyperosmotic or hypoosmotic environment
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• Most animals are stenohaline; they cannot tolerate substantial changes in external osmolarity
• Euryhaline animals can survive large fluctuations in external osmolarity
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Fig. 44-3
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Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Marine Animals
• Most marine invertebrates are osmoconformers
• Most marine vertebrates and some invertebrates are osmoregulators
• Marine bony fishes are hypoosmotic to sea water
• They lose water by osmosis and gain salt by diffusion and from food
• They balance water loss by drinking seawater and excreting salts
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Fig. 44-4
Excretionof salt ionsfrom gills
Gain of water andsalt ions from food
Osmotic waterloss through gillsand other partsof body surface
Uptake of water andsome ions in food
Uptakeof salt ionsby gills
Osmotic watergain through gillsand other partsof body surface
Excretion of largeamounts of water indilute urine from kidneys
Excretion of salt ions andsmall amounts of water inscanty urine from kidneys
Gain of waterand salt ions fromdrinking seawater
(a) Osmoregulation in a saltwater fish (b) Osmoregulation in a freshwater fish
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Fig. 44-4a
Excretionof salt ionsfrom gills
Gain of water andsalt ions from food
Osmotic waterloss through gillsand other partsof body surface
Excretion of salt ions andsmall amounts of water inscanty urine from kidneys
Gain of waterand salt ions fromdrinking seawater
(a) Osmoregulation in a saltwater fish
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Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Freshwater Animals
• Freshwater animals constantly take in water by osmosis from their hypoosmotic environment
• They lose salts by diffusion and maintain water balance by excreting large amounts of dilute urine
• Salts lost by diffusion are replaced in foods and by uptake across the gills
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Fig. 44-4b
Uptake of water andsome ions in food
Uptakeof salt ionsby gills
Osmotic watergain through gillsand other partsof body surface
Excretion of largeamounts of water indilute urine from kidneys
(b) Osmoregulation in a freshwater fish
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Animals That Live in Temporary Waters
• Some aquatic invertebrates in temporary ponds lose almost all their body water and survive in a dormant state
• This adaptation is called anhydrobiosis
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Fig. 44-5
(a) Hydrated tardigrade (b) Dehydrated tardigrade
100 µm
100 µm
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Land Animals
• Land animals manage water budgets by drinking and eating moist foods and using metabolic water
• Desert animals get major water savings from simple anatomical features and behaviors such as a nocturnal life style
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Fig. 44-6
Watergain(mL)
Waterloss(mL)
Urine(0.45)
Urine(1,500)
Evaporation (1.46) Evaporation (900)
Feces (0.09) Feces (100)
Derived frommetabolism (1.8)
Derived frommetabolism (250)
Ingestedin food (750)
Ingestedin food (0.2)
Ingestedin liquid (1,500)
Waterbalance in akangaroo rat(2 mL/day)
Waterbalance ina human(2,500 mL/day)
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Energetics of Osmoregulation
• Osmoregulators must expend energy to maintain osmotic gradients
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Transport Epithelia in Osmoregulation
• Animals regulate the composition of body fluid that bathes their cells
• Transport epithelia are specialized epithelial cells that regulate solute movement
• They are essential components of osmotic regulation and metabolic waste disposal
• They are arranged in complex tubular networks
• An example is in salt glands of marine birds, which remove excess sodium chloride from the blood
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Fig. 44-7
Ducts
Nostrilwith saltsecretions
Nasal saltgland
EXPERIMENT
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Fig. 44-8
Salt gland
Secretorycell
Capillary
Secretory tubule
Transportepithelium
Direction ofsalt movement
Central duct
(a)
Bloodflow
(b)
Secretorytubule
ArteryVein
NaCl
NaCl
Salt secretion
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Concept 44.2: An animal’s nitrogenous wastes reflect its phylogeny and habitat
• The type and quantity of an animal’s waste products may greatly affect its water balance
• Among the most important wastes are nitrogenous breakdown products of proteins and nucleic acids
• Some animals convert toxic ammonia (NH3) to less toxic compounds prior to excretion
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Fig. 44-9
Many reptiles(including birds),insects, land snails
Ammonia Uric acidUrea
Most aquaticanimals, includingmost bony fishes
Mammals, mostamphibians, sharks,some bony fishes
Nitrogenous bases
Amino acids
Proteins Nucleic acids
Amino groups
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Concept 44.3: Diverse excretory systems are variations on a tubular theme
• Excretory systems regulate solute movement between internal fluids and the external environment
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Excretory Processes
• Most excretory systems produce urine by refining a filtrate derived from body fluids
• Key functions of most excretory systems:
– Filtration: pressure-filtering of body fluids
– Reabsorption: reclaiming valuable solutes
– Secretion: adding toxins and other solutes from the body fluids to the filtrate
– Excretion: removing the filtrate from the system
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Fig. 44-10
Capillary
Excretion
Secretion
Reabsorption
Excretorytubule
Filtration
Filtrate
Urin
e
Concept 44.3: Diverse excretory systems are variations on a tubular theme
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Survey of Excretory Systems
• Systems that perform basic excretory functions vary widely among animal groups
• They usually involve a complex network of tubules
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Protonephridia
• A protonephridium is a network of dead-end tubules connected to external openings
• The smallest branches of the network are capped by a cellular unit called a flame bulb
• These tubules excrete a dilute fluid and function in osmoregulation
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Fig. 44-11
Tubule
Tubules ofprotonephridia
Cilia
Interstitialfluid flow
Opening inbody wall
Nucleusof cap cell
Flamebulb
Tubule cell
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Metanephridia
• Each segment of an earthworm has a pair of open-ended metanephridia
• Metanephridia consist of tubules that collect coelomic fluid and produce dilute urine for excretion
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Fig. 44-12
Capillarynetwork
Components ofa metanephridium:
External opening
Coelom
Collecting tubule
Internal opening
Bladder
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Malpighian Tubules
• In insects and other terrestrial arthropods, Malpighian tubules remove nitrogenous wastes from hemolymph and function in osmoregulation
• Insects produce a relatively dry waste matter, an important adaptation to terrestrial life
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Fig. 44-13
Rectum
Digestive tract
HindgutIntestine
Malpighiantubules
Rectum
Feces and urine
HEMOLYMPH
Reabsorption
Midgut(stomach)
Salt, water, and nitrogenous
wastes
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Kidneys
• Kidneys, the excretory organs of vertebrates, function in both excretion and osmoregulation
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Structure of the Mammalian Excretory System
• The mammalian excretory system centers on paired kidneys, which are also the principal site of water balance and salt regulation
• Each kidney is supplied with blood by a renal artery and drained by a renal vein
• Urine exits each kidney through a duct called the ureter
• Both ureters drain into a common urinary bladder, and urine is expelled through a urethra
Animation: Nephron Introduction
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Fig. 44-14
Posteriorvena cava
Renal arteryand vein
Urinarybladder
Ureter
Aorta
Urethra
Kidney
(a) Excretory organs and major associated blood vessels
Corticalnephron
Juxtamedullarynephron
Collectingduct
(c) Nephron types
Torenalpelvis
Renalmedulla
Renalcortex
10 µm
Afferent arteriolefrom renal artery
Efferentarteriole fromglomerulus
SEM
Branch ofrenal vein
Descendinglimb
Ascendinglimb
Loop ofHenle
(d) Filtrate and blood flow
Vasarecta
Collectingduct
Distaltubule
Peritubular capillaries
Proximal tubuleBowman’s capsule
Glomerulus
Ureter
Renal medulla
Renal cortex
Renal pelvis
(b) Kidney structure Section of kidneyfrom a rat 4 mm
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Fig. 44-15
Key
ActivetransportPassivetransport
INNERMEDULLA
OUTERMEDULLA
H2O
CORTEX
Filtrate
Loop ofHenle
H2O K+HCO3–
H+ NH3
Proximal tubule
NaCl Nutrients
Distal tubule
K+ H+
HCO3–
H2O
H2O
NaCl
NaCl
NaCl
NaCl
Urea
Collectingduct
NaCl
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Solute Gradients and Water Conservation
• Urine is much more concentrated than blood
• The cooperative action and precise arrangement of the loops of Henle and collecting ducts are largely responsible for the osmotic gradient that concentrates the urine
• NaCl and urea contribute to the osmolarity of the interstitial fluid, which causes reabsorption of water in the kidney and concentrates the urine
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The Two-Solute Model
• In the proximal tubule, filtrate volume decreases, but its osmolarity remains the same
• The countercurrent multiplier system involving the loop of Henle maintains a high salt concentration in the kidney
• This system allows the vasa recta to supply the kidney with nutrients, without interfering with the osmolarity gradient
• Considerable energy is expended to maintain the osmotic gradient between the medulla and cortex
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• The collecting duct conducts filtrate through the osmolarity gradient, and more water exits the filtrate by osmosis
• Urea diffuses out of the collecting duct as it traverses the inner medulla
• Urea and NaCl form the osmotic gradient that enables the kidney to produce urine that is hyperosmotic to the blood
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Fig. 44-16-3
Key
Activetransport
Passivetransport
INNERMEDULLA
OUTERMEDULLA
CORTEXH2O
300300
300
H2O
H2O
H2O
400
600
900
H2O
H2O
1,200
H2O
300
Osmolarity ofinterstitial
fluid(mOsm/L)
400
600
900
1,200
100
NaCl
100
NaCl
NaCl
NaCl
NaCl
NaCl
NaCl
200
400
700
1,200
300
400
600
H2O
H2O
H2O
H2O
H2O
H2O
H2O
NaCl
NaCl
Urea
Urea
Urea
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Adaptations of the Vertebrate Kidney to Diverse Environments
• The form and function of nephrons in various vertebrate classes are related to requirements for osmoregulation in the animal’s habitat
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Mammals
• The juxtamedullary nephron contributes to water conservation in terrestrial animals
• Mammals that inhabit dry environments have long loops of Henle, while those in fresh water have relatively short loops
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Birds and Other Reptiles
• Birds have shorter loops of Henle but conserve water by excreting uric acid instead of urea
• Other reptiles have only cortical nephrons but also excrete nitrogenous waste as uric acid
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Fig. 44-17
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Freshwater Fishes and Amphibians
• Freshwater fishes conserve salt in their distal tubules and excrete large volumes of dilute urine
• Kidney function in amphibians is similar to freshwater fishes
• Amphibians conserve water on land by reabsorbing water from the urinary bladder
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Marine Bony Fishes
• Marine bony fishes are hypoosmotic compared with their environment and excrete very little urine
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Concept 44.5: Hormonal circuits link kidney function, water balance, and blood pressure
• Mammals control the volume and osmolarity of urine
• The kidneys of the South American vampire bat can produce either very dilute or very concentrated urine
• This allows the bats to reduce their body weight rapidly or digest large amounts of protein while conserving water
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Fig. 44-18
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Antidiuretic Hormone
• The osmolarity of the urine is regulated by nervous and hormonal control of water and salt reabsorption in the kidneys
• Antidiuretic hormone (ADH) increases water reabsorption in the distal tubules and collecting ducts of the kidney
• An increase in osmolarity triggers the release of ADH, which helps to conserve water
Animation: Effect of ADH
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Fig. 44-19
Thirst
Drinking reducesblood osmolarity
to set point.
Osmoreceptors in hypothalamus trigger
release of ADH.
Increasedpermeability
Pituitarygland
ADH
Hypothalamus
Distaltubule
H2O reab-sorption helpsprevent further
osmolarityincrease.
STIMULUS:Increase in blood
osmolarity
Collecting duct
Homeostasis:Blood osmolarity
(300 mOsm/L)
(a)
Exocytosis
(b)
Aquaporinwaterchannels
H2O
H2O
Storagevesicle
Second messengersignaling molecule
cAMP
INTERSTITIALFLUID
ADHreceptor
ADH
COLLECTINGDUCTLUMEN
COLLECTINGDUCT CELL
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• Mutation in ADH production causes severe dehydration and results in diabetes insipidus
• Alcohol is a diuretic as it inhibits the release of ADH
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Fig. 44-20
Prepare copiesof human aqua-porin genes.
196
Transfer to10 mOsmsolution.
SynthesizeRNAtranscripts.
EXPERIMENT
Mutant 1 Mutant 2
Aquaporingene
Promoter
Wild type
H2O(control)
Inject RNAinto frogoocytes.
Aquaporinprotein
RESULTS
20
17
18
Permeability (µm/s)Injected RNA
Wild-type aquaporin
None
Aquaporin mutant 1
Aquaporin mutant 2
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The Renin-Angiotensin-Aldosterone System
• The renin-angiotensin-aldosterone system (RAAS) is part of a complex feedback circuit that functions in homeostasis
• A drop in blood pressure near the glomerulus causes the juxtaglomerular apparatus (JGA) to release the enzyme renin
• Renin triggers the formation of the peptide angiotensin II
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• Angiotensin II
– Raises blood pressure and decreases blood flow to the kidneys
– Stimulates the release of the hormone aldosterone, which increases blood volume and pressure
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Fig. 44-21-3
Renin
Distaltubule
Juxtaglomerularapparatus (JGA)
STIMULUS:Low blood volumeor blood pressure
Homeostasis:Blood pressure,
volume
Liver
Angiotensinogen
Angiotensin I
ACE
Angiotensin II
Adrenal gland
Aldosterone
Arterioleconstriction
Increased Na+
and H2O reab-sorption in
distal tubules
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Homeostatic Regulation of the Kidney
• ADH and RAAS both increase water reabsorption, but only RAAS will respond to a decrease in blood volume
• Another hormone, atrial natriuretic peptide (ANP), opposes the RAAS
• ANP is released in response to an increase in blood volume and pressure and inhibits the release of renin
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Fig. 44-UN1
Animal
Freshwaterfish
Bony marinefish
Terrestrialvertebrate
H2O andsalt out
Salt in(by mouth)
Drinks water
Salt out (activetransport by gills)
Drinks waterSalt in H2O out
Salt out
Salt in H2O in(active trans-port by gills)
Does not drink water
Inflow/Outflow Urine
Large volumeof urine
Urine is lessconcentratedthan bodyfluids
Small volumeof urine
Urine isslightly lessconcentratedthan bodyfluids
Moderatevolumeof urine
Urine ismoreconcentratedthan bodyfluids
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PowerPoint® Lecture Presentations for
Biology Eighth Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp
Chapter 45Chapter 45
Hormones and theEndocrine System
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Overview: The Body’s Long-Distance Regulators
• Animal hormones are chemical signals that are secreted into the circulatory system and communicate regulatory messages within the body
• Hormones reach all parts of the body, but only target cells are equipped to respond
• Insect metamorphosis is regulated by hormones
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• Two systems coordinate communication throughout the body: the endocrine system and the nervous system
• The endocrine system secretes hormones that coordinate slower but longer-acting responses including reproduction, development, energy metabolism, growth, and behavior
• The nervous system conveys high-speed electrical signals along specialized cells called neurons; these signals regulate other cells
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Concept 45.1: Hormones and other signaling molecules bind to target receptors, triggering specific response pathways
• Chemical signals bind to receptor proteins on target cells
• Only target cells respond to the signal
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Fig. 45-2a
Bloodvessel Response
Response
Response
(a) Endocrine signaling
(b) Paracrine signaling
(c) Autocrine signaling
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Fig. 45-2b
Response
(d) Synaptic signaling
Neuron
Neurosecretorycell
(e) Neuroendocrine signaling
Bloodvessel
Synapse
Response
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Pheromones
• Pheromones are chemical signals that are released from the body and used to communicate with other individuals in the species
• Pheromones mark trails to food sources, warn of predators, and attract potential mates
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Fig. 45-3
Water-soluble Lipid-soluble
Steroid:Cortisol
Polypeptide:Insulin
Amine:Epinephrine
Amine:Thyroxine
0.8 nm
Chemical Classes of Hormones
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Hormone Receptor Location: Scientific Inquiry
• In the 1960s, researchers studied the accumulation of radioactive steroid hormones in rat tissue
• These hormones accumulated only in target cells that were responsive to the hormones
• These experiments led to the hypothesis that receptors for the steroid hormones are located inside the target cells
• Further studies have confirmed that receptors for lipid-soluble hormones such as steroids are located inside cells
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• Researchers hypothesized that receptors for water-soluble hormones would be located on the cell surface
• They injected a water-soluble hormone into the tissues of frogs
• The hormone triggered a response only when it was allowed to bind to cell surface receptors
• This confirmed that water-soluble receptors were on the cell surface
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Fig. 45-4
MSH injected into melanocyte
Nucleus
Melanosomesdo not disperse
MSH injected into interstitial fluid (blue)
Melanosomesdisperse
Melanocytewith melanosomes(black dots)
RESULTS
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Cellular Response Pathways
• Water and lipid soluble hormones differ in their paths through a body
• Water-soluble hormones are secreted by exocytosis, travel freely in the bloodstream, and bind to cell-surface receptors
• Lipid-soluble hormones diffuse across cell membranes, travel in the bloodstream bound to transport proteins, and diffuse through the membrane of target cells
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• Signaling by any of these hormones involves three key events:
– Reception
– Signal transduction
– Response
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Fig. 45-5-2
Signalreceptor
TARGETCELL
Signal receptor
Transportprotein
Water-solublehormone
Fat-solublehormone
Generegulation
Cytoplasmicresponse
Generegulation
Cytoplasmicresponse
OR
(a) NUCLEUS (b)
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Multiple Effects of Hormones
• The same hormone may have different effects on target cells that have
– Different receptors for the hormone
– Different signal transduction pathways
– Different proteins for carrying out the response
• A hormone can also have different effects in different species
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Fig. 45-8-2
Glycogendeposits
receptor
Vesseldilates.
Epinephrine
(a) Liver cell
Epinephrine
receptor
Glycogenbreaks downand glucoseis released.
(b) Skeletal muscle blood vessel
Same receptors but differentintracellular proteins (not shown)
Epinephrine
receptor
Different receptors
Epinephrine
receptor
Vesselconstricts.
(c) Intestinal blood vessel
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Signaling by Local Regulators
• In paracrine signaling, nonhormonal chemical signals called local regulators elicit responses in nearby target cells
• Types of local regulators:
– Cytokines and growth factors
– Nitric oxide (NO)
– Prostaglandins
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• Prostaglandins help regulate aggregation of platelets, an early step in formation of blood clots
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Concept 45.2: Negative feedback and antagonistic hormone pairs are common features of the endocrine system
• Hormones are assembled into regulatory pathways
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Fig. 45-10Major endocrine glands:
Adrenalglands
Hypothalamus
Pineal gland
Pituitary gland
Thyroid gland
Parathyroid glands
Pancreas
Kidney
Ovaries
Testes
Organs containingendocrine cells:
Thymus
Heart
Liver
Stomach
Kidney
Smallintestine
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Insulin and Glucagon: Control of Blood Glucose
• Insulin and glucagon are antagonistic hormones that help maintain glucose homeostasis
• The pancreas has clusters of endocrine cells called islets of Langerhans with alpha cells that produce glucagon and beta cells that produce insulin
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Fig. 45-12-5
Homeostasis:Blood glucose level
(about 90 mg/100 mL)
Glucagon
STIMULUS:Blood glucose level
falls.
Alpha cells of pancreasrelease glucagon.
Liver breaksdown glycogenand releasesglucose.
Blood glucoselevel rises.
STIMULUS:Blood glucose level
rises.
Beta cells ofpancreasrelease insulininto the blood.
Liver takesup glucoseand stores itas glycogen.
Blood glucoselevel declines.
Body cellstake up moreglucose.
Insulin
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Concept 45.3: The endocrine and nervous systems act individually and together in regulating animal physiology
• Signals from the nervous system initiate and regulate endocrine signals
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Coordination of Endocrine and Nervous Systems in Invertebrates
• In insects, molting and development are controlled by a combination of hormones:
– A brain hormone stimulates release of ecdysone from the prothoracic glands
– Juvenile hormone promotes retention of larval characteristics
– Ecdysone promotes molting (in the presence of juvenile hormone) and development (in the absence of juvenile hormone) of adult characteristics
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Fig. 45-13-3
Ecdysone
Brain
PTTH
EARLYLARVA
Neurosecretory cells
Corpus cardiacum
Corpus allatum
LATERLARVA PUPA ADULT
LowJH
Juvenilehormone(JH)
Prothoracicgland
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Coordination of Endocrine and Nervous Systems in Vertebrates
• The hypothalamus receives information from the nervous system and initiates responses through the endocrine system
• Attached to the hypothalamus is the pituitary gland composed of the posterior pituitary and anterior pituitary
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• The posterior pituitary stores and secretes hormones that are made in the hypothalamus
• The anterior pituitary makes and releases hormones under regulation of the hypothalamus
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Fig. 45-14
Spinal cord
Posteriorpituitary
Cerebellum
Pinealgland
Anteriorpituitary
Hypothalamus
Pituitarygland
Hypothalamus
Thalamus
Cerebrum
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Table 45-1b
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Table 45-1c
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Table 45-1d
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Posterior Pituitary Hormones
• The two hormones released from the posterior pituitary act directly on nonendocrine tissues
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Fig. 45-15
Posteriorpituitary
Anteriorpituitary
Neurosecretorycells of thehypothalamus
Hypothalamus
Axon
HORMONE OxytocinADH
Kidney tubulesTARGET Mammary glands,uterine muscles
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• Oxytocin induces uterine contractions and the release of milk
• Suckling sends a message to the hypothalamus via the nervous system to release oxytocin, which further stimulates the milk glands
• This is an example of positive feedback, where the stimulus leads to an even greater response
• Antidiuretic hormone (ADH) enhances water reabsorption in the kidneys
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Anterior Pituitary Hormones
• Hormone production in the anterior pituitary is controlled by releasing and inhibiting hormones from the hypothalamus
• For example, the production of thyrotropin releasing hormone (TRH) in the hypothalamus stimulates secretion of the thyroid stimulating hormone (TSH) from the anterior pituitary
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Fig. 45-17
Hypothalamicreleasing andinhibitinghormones
Neurosecretory cellsof the hypothalamus
HORMONE
TARGET
Posterior pituitary
Portal vessels
Endocrine cells ofthe anterior pituitary
Pituitary hormones
Tropic effects only:FSHLHTSHACTH
Nontropic effects only:ProlactinMSH
Nontropic and tropic effects:GH
Testes orovaries
Thyroid
FSH and LH TSH
Adrenalcortex
Mammaryglands
ACTH Prolactin MSH GH
Melanocytes Liver, bones,other tissues
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Hormone Cascade Pathways
• A hormone can stimulate the release of a series of other hormones, the last of which activates a nonendocrine target cell; this is called a hormone cascade pathway
• The release of thyroid hormone results from a hormone cascade pathway involving the hypothalamus, anterior pituitary, and thyroid gland
• Hormone cascade pathways are usually regulated by negative feedback
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Fig. 45-18-3
Cold
Pathway
Stimulus
Hypothalamus secretesthyrotropin-releasinghormone (TRH )
Neg
ativ
e fe
edb
ack
Example
Sensoryneuron
Neurosecretorycell
Bloodvessel
Anterior pituitary secretes thyroid-stimulatinghormone (TSHor thyrotropin )
Targetcells
Response
Body tissues
Increased cellularmetabolism
–
Thyroid gland secretes thyroid hormone (T3 and T4 )
–
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Tropic Hormones
• A tropic hormone regulates the function of endocrine cells or glands
• The four strictly tropic hormones are
– Thyroid-stimulating hormone (TSH)
– Follicle-stimulating hormone (FSH)
– Luteinizing hormone (LH)
– Adrenocorticotropic hormone (ACTH)
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Nontropic Hormones
• Nontropic hormones target nonendocrine tissues
• Nontropic hormones produced by the anterior pituitary are
– Prolactin (PRL)
– Melanocyte-stimulating hormone (MSH)
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• Prolactin stimulates lactation in mammals but has diverse effects in different vertebrates
• MSH influences skin pigmentation in some vertebrates and fat metabolism in mammals
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Growth Hormone
• Growth hormone (GH) is secreted by the anterior pituitary gland and has tropic and nontropic actions
• It promotes growth directly and has diverse metabolic effects
• It stimulates production of growth factors
• An excess of GH can cause gigantism, while a lack of GH can cause dwarfism
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• Endocrine signaling regulates metabolism, homeostasis, development, and behavior
Concept 45.4: Endocrine glands respond to diverse stimuli in regulating metabolism, homeostasis, development, and behavior
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Thyroid Hormone: Control of Metabolism and Development
• The thyroid gland consists of two lobes on the ventral surface of the trachea
• It produces two iodine-containing hormones: triiodothyronine (T3) and thyroxine (T4)
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• Thyroid hormones stimulate metabolism and influence development and maturation
• Hyperthyroidism, excessive secretion of thyroid hormones, causes high body temperature, weight loss, irritability, and high blood pressure
• Graves’ disease is a form of hyperthyroidism in humans
• Hypothyroidism, low secretion of thyroid hormones, causes weight gain, lethargy, and intolerance to cold
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Fig. 45-19
Normaliodineuptake
High leveliodineuptake
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• Proper thyroid function requires dietary iodine for hormone production
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Parathyroid Hormone and Vitamin D: Control of Blood Calcium
• Two antagonistic hormones regulate the homeostasis of calcium (Ca2+) in the blood of mammals
– Parathyroid hormone (PTH) is released by the parathyroid glands
– Calcitonin is released by the thyroid gland
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Fig. 45-20-2
PTH
Parathyroid gland(behind thyroid)
STIMULUS:Falling blood
Ca2+ level
Homeostasis:Blood Ca2+ level
(about 10 mg/100 mL)
Blood Ca2+ level rises.
Stimulates Ca2+
uptake in kidneys
Stimulates Ca2+ release from bones
Increases Ca2+ uptake in intestines
Activevitamin D
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Adrenal Hormones: Response to Stress
• The adrenal glands are adjacent to the kidneys
• Each adrenal gland actually consists of two glands: the adrenal medulla (inner portion) and adrenal cortex (outer portion)
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Catecholamines from the Adrenal Medulla
• The adrenal medulla secretes epinephrine (adrenaline) and norepinephrine (noradrenaline)
• These hormones are members of a class of compounds called catecholamines
• They are secreted in response to stress-activated impulses from the nervous system
• They mediate various fight-or-flight responses
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• Epinephrine and norepinephrine
– Trigger the release of glucose and fatty acids into the blood
– Increase oxygen delivery to body cells
– Direct blood toward heart, brain, and skeletal muscles, and away from skin, digestive system, and kidneys
• The release of epinephrine and norepinephrine occurs in response to nerve signals from the hypothalamus
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Fig. 45-21
Stress
Adrenalgland
Nervecell
Nervesignals
Releasinghormone
Hypothalamus
Anterior pituitary
Blood vessel
ACTH
Adrenal cortex
Spinal cord
Adrenal medulla
Kidney
(a) Short-term stress response (b) Long-term stress response
Effects of epinephrine and norepinephrine:
2. Increased blood pressure
3. Increased breathing rate
4. Increased metabolic rate
1. Glycogen broken down to glucose; increased blood glucose
5. Change in blood flow patterns, leading to increased alertness and decreased digestive, excretory, and reproductive system activity
Effects ofmineralocorticoids:
Effects ofglucocorticoids:
1. Retention of sodium ions and water by kidneys
2. Increased blood volume and blood pressure
2. Possible suppression of immune system
1. Proteins and fats broken down and converted to glucose, leading to increased blood glucose
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Steroid Hormones from the Adrenal Cortex
• The adrenal cortex releases a family of steroids called corticosteroids in response to stress
• These hormones are triggered by a hormone cascade pathway via the hypothalamus and anterior pituitary
• Humans produce two types of corticosteroids: glucocorticoids and mineralocorticoids
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• Glucocorticoids, such as cortisol, influence glucose metabolism and the immune system
• Mineralocorticoids, such as aldosterone, affect salt and water balance
• The adrenal cortex also produces small amounts of steroid hormones that function as sex hormones
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Gonadal Sex Hormones
• The gonads, testes and ovaries, produce most of the sex hormones: androgens, estrogens, and progestins
• All three sex hormones are found in both males and females, but in different amounts
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• The testes primarily synthesize androgens, mainly testosterone, which stimulate development and maintenance of the male reproductive system
• Testosterone causes an increase in muscle and bone mass and is often taken as a supplement to cause muscle growth, which carries health risks
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Fig. 45-22
Embryonicgonad removed
Chromosome Set
Appearance of Genitals
XY (male)
XX (female)
Male
Female Female
Female
No surgery
RESULTS
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• Estrogens, most importantly estradiol, are responsible for maintenance of the female reproductive system and the development of female secondary sex characteristics
• In mammals, progestins, which include progesterone, are primarily involved in preparing and maintaining the uterus
• Synthesis of the sex hormones is controlled by FSH and LH from the anterior pituitary
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Melatonin and Biorhythms
• The pineal gland, located in the brain, secretes melatonin
• Light/dark cycles control release of melatonin
• Primary functions of melatonin appear to relate to biological rhythms associated with reproduction
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Fig. 45-UN2Pathway Example
Stimulus Low blood glucose
Pancreas secretes glucagon ( )
Endocrinecell
Bloodvessel
LiverTargetcells
ResponseGlycogen breakdown,glucose releaseinto blood
Neg
ativ
e fe
edb
ack
–