chapter 44

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

Fig. 44-1

Osmoregulation regulates solute concentrations and balances the gain and loss of water

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

Fig. 44-2

Selectively permeablemembrane

Net water flow

Hyperosmotic side Hypoosmotic side

Water

Solutes


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


• Most animals are stenohaline; they cannot tolerate substantial changes in external osmolarity

• Euryhaline animals can survive large fluctuations in external osmolarity

Fig. 44-3


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

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

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


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

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


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

Fig. 44-5

(a) Hydrated tardigrade (b) Dehydrated tardigrade

100 µm

100 µm


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

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)


Energetics of Osmoregulation

• Osmoregulators must expend energy to maintain osmotic gradients


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

Fig. 44-7

Ducts

Nostrilwith saltsecretions

Nasal saltgland

EXPERIMENT

Fig. 44-8

Salt gland

Secretorycell

Capillary

Secretory tubule

Transportepithelium

Direction ofsalt movement

Central duct

(a)

Bloodflow

(b)

Secretorytubule

ArteryVein

NaCl

NaCl

Salt secretion


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

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


Concept 44.3: Diverse excretory systems are variations on a tubular theme

• Excretory systems regulate solute movement between internal fluids and the external environment


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

Fig. 44-10

Capillary

Excretion

Secretion

Reabsorption

Excretorytubule

Filtration

Filtrate

Urin

e

Concept 44.3: Diverse excretory systems are variations on a tubular theme


Survey of Excretory Systems

• Systems that perform basic excretory functions vary widely among animal groups

• They usually involve a complex network of tubules


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

Fig. 44-11

Tubule

Tubules ofprotonephridia

Cilia

Interstitialfluid flow

Opening inbody wall

Nucleusof cap cell

Flamebulb

Tubule cell


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

Fig. 44-12

Capillarynetwork

Components ofa metanephridium:

External opening

Coelom

Collecting tubule

Internal opening

Bladder


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

Fig. 44-13

Rectum

Digestive tract

HindgutIntestine

Malpighiantubules

Rectum

Feces and urine

HEMOLYMPH

Reabsorption

Midgut(stomach)

Salt, water, and nitrogenous

wastes


Kidneys

• Kidneys, the excretory organs of vertebrates, function in both excretion and osmoregulation


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

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

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


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


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


• 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

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


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


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


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

Fig. 44-17


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


Marine Bony Fishes

• Marine bony fishes are hypoosmotic compared with their environment and excrete very little urine


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

Fig. 44-18


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

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


• Mutation in ADH production causes severe dehydration and results in diabetes insipidus

• Alcohol is a diuretic as it inhibits the release of ADH

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


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


• 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

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


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

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

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 45Chapter 45

Hormones and theEndocrine System


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


• 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


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


Fig. 45-2a

Bloodvessel Response

Response

Response

(a) Endocrine signaling

(b) Paracrine signaling

(c) Autocrine signaling


Fig. 45-2b

Response

(d) Synaptic signaling

Neuron

Neurosecretorycell

(e) Neuroendocrine signaling

Bloodvessel

Synapse

Response


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


Fig. 45-3

Water-soluble Lipid-soluble

Steroid:Cortisol

Polypeptide:Insulin

Amine:Epinephrine

Amine:Thyroxine

0.8 nm

Chemical Classes of Hormones


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


• 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


Fig. 45-4

MSH injected into melanocyte

Nucleus

Melanosomesdo not disperse

MSH injected into interstitial fluid (blue)

Melanosomesdisperse

Melanocytewith melanosomes(black dots)

RESULTS


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


• Signaling by any of these hormones involves three key events:

– Reception

– Signal transduction

– Response


Fig. 45-5-2

Signalreceptor

TARGETCELL

Signal receptor

Transportprotein

Water-solublehormone

Fat-solublehormone

Generegulation

Cytoplasmicresponse

Generegulation

Cytoplasmicresponse

OR

(a) NUCLEUS (b)


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


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


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


• Prostaglandins help regulate aggregation of platelets, an early step in formation of blood clots


Concept 45.2: Negative feedback and antagonistic hormone pairs are common features of the endocrine system

• Hormones are assembled into regulatory pathways


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


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


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


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


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


Fig. 45-13-3

Ecdysone

Brain

PTTH

EARLYLARVA

Neurosecretory cells

Corpus cardiacum

Corpus allatum

LATERLARVA PUPA ADULT

LowJH

Juvenilehormone(JH)

Prothoracicgland


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


• 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


Fig. 45-14

Spinal cord

Posteriorpituitary

Cerebellum

Pinealgland

Anteriorpituitary

Hypothalamus

Pituitarygland

Hypothalamus

Thalamus

Cerebrum


Table 45-1b


Table 45-1c


Table 45-1d


Posterior Pituitary Hormones

• The two hormones released from the posterior pituitary act directly on nonendocrine tissues


Fig. 45-15

Posteriorpituitary

Anteriorpituitary

Neurosecretorycells of thehypothalamus

Hypothalamus

Axon

HORMONE OxytocinADH

Kidney tubulesTARGET Mammary glands,uterine muscles


• 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


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


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


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


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 )

–


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)


Nontropic Hormones

• Nontropic hormones target nonendocrine tissues

• Nontropic hormones produced by the anterior pituitary are

– Prolactin (PRL)

– Melanocyte-stimulating hormone (MSH)


• Prolactin stimulates lactation in mammals but has diverse effects in different vertebrates

• MSH influences skin pigmentation in some vertebrates and fat metabolism in mammals


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


• Endocrine signaling regulates metabolism, homeostasis, development, and behavior

Concept 45.4: Endocrine glands respond to diverse stimuli in regulating metabolism, homeostasis, development, and behavior


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)


• 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


Fig. 45-19

Normaliodineuptake

High leveliodineuptake


• Proper thyroid function requires dietary iodine for hormone production


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


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


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)


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


• 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


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


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


• 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


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


• 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


Fig. 45-22

Embryonicgonad removed

Chromosome Set

Appearance of Genitals

XY (male)

XX (female)

Male

Female Female

Female

No surgery

RESULTS


• 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


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


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

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chapter 44

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