PowerLecture: Chapter 15

PowerLecture:PowerLecture:Chapter 15Chapter 15

The Endocrine SystemThe Endocrine System

Learning ObjectivesLearning Objectives

Know the general mechanisms by which Know the general mechanisms by which molecules integrate and control the various molecules integrate and control the various metabolic activities in organisms.metabolic activities in organisms.

Understand how the neuro-endocrine Understand how the neuro-endocrine center controls secretion rates of other center controls secretion rates of other endocrine glands and responses in nerves endocrine glands and responses in nerves and muscles.and muscles.

Know the major endocrine glands and their Know the major endocrine glands and their secretions.secretions.

Learning Objectives (cont’d)Learning Objectives (cont’d)

Know how sugar levels are regulated by Know how sugar levels are regulated by hormones.hormones.

Differentiate the modes of action of steroid Differentiate the modes of action of steroid and nonsteroid hormones.and nonsteroid hormones.

Impacts/IssuesImpacts/Issues

Hormones in the Hormones in the BalanceBalance

Hormones in the Balance Hormones in the Balance

Arsenic may be an endocrine disrupter, Arsenic may be an endocrine disrupter, especially of glucocorticoids.especially of glucocorticoids.

Glucocorticoids in turn regulate genes that Glucocorticoids in turn regulate genes that protect against cancer.protect against cancer.

This may be the link between the consumption This may be the link between the consumption of arsenic in water supplies and increased rates of arsenic in water supplies and increased rates of bladder, lung, and skin cancersof bladder, lung, and skin cancers..

Hormones in the Balance Hormones in the Balance

Other endocrine disrupters are also coming Other endocrine disrupters are also coming under scrutiny.under scrutiny.

The herbicide atrazine has been widely used on The herbicide atrazine has been widely used on crops and turf grasses.crops and turf grasses.

PCBs, used for many years as fluid insulation in PCBs, used for many years as fluid insulation in electrical transformers, have been banned but electrical transformers, have been banned but still persist in the environment, where they are still persist in the environment, where they are linked to reproductive disorders in humans and linked to reproductive disorders in humans and animals.animals.

Research is continuing on endocrine Research is continuing on endocrine disrupters; the jury is still out.disrupters; the jury is still out.

Useful References for Impacts/IssuesUseful References for Impacts/Issues

The latest references for topics covered in this section can be found at The latest references for topics covered in this section can be found at the the book companion websitebook companion website. Log in to the book’s e-resources page at . Log in to the book’s e-resources page at www.thomsonedu.comwww.thomsonedu.com to access InfoTrac articles. to access InfoTrac articles.

EPA: Endocrine Disruptors Research EPA: Endocrine Disruptors Research InitiativeInitiative

InfoTrac: New Report Points Up Growing InfoTrac: New Report Points Up Growing Evidence of Endocrine Disrupters. Evidence of Endocrine Disrupters. European European ReportReport, May 4, 2006., May 4, 2006.

How Would You Vote?How Would You Vote?To conduct an instant in-class survey using a classroom response To conduct an instant in-class survey using a classroom response system, access “JoinIn Clicker Content” from the PowerLecture main system, access “JoinIn Clicker Content” from the PowerLecture main menu. menu.

Some pesticides may disrupt hormone Some pesticides may disrupt hormone function in humans and other animals. function in humans and other animals. Should they remain in use while researchers Should they remain in use while researchers study their safety?study their safety? a. No, they could be dangerous; until we know for a. No, they could be dangerous; until we know for

sure, it is better to be safe than sorry. sure, it is better to be safe than sorry. b. Yes, banning them because of potential harm b. Yes, banning them because of potential harm

isn't fair; there should be solid evidence first. isn't fair; there should be solid evidence first.

Useful References for Useful References for How Would You Vote?How Would You Vote?


InfoTrac: Endocrine Disruption Study on InfoTrac: Endocrine Disruption Study on Atrazine Disputed. Atrazine Disputed. Pesticide & Toxic Pesticide & Toxic Chemical News, Chemical News, Jan. 13, 2003.Jan. 13, 2003.

Water Conserve 2.0: Chemical Affecting Water Conserve 2.0: Chemical Affecting Frogs’ Sexuality; Males Are Acquiring Frogs’ Sexuality; Males Are Acquiring Female Attributes after Exposure to a Female Attributes after Exposure to a Common Weedkiller, Study SaysCommon Weedkiller, Study Says

Section 1Section 1

The Endocrine System: The Endocrine System: HormonesHormones

The Endocrine System: Hormones The Endocrine System: Hormones

Hormones are signaling molecules that are Hormones are signaling molecules that are carried in the bloodstream.carried in the bloodstream.

Signaling molecules are hormones and Signaling molecules are hormones and secretions that can bind to secretions that can bind to target cellstarget cells and and elicit in them a response.elicit in them a response.

HormonesHormones are secreted by endocrine glands, are secreted by endocrine glands, endocrine cells, and some neurons.endocrine cells, and some neurons.

Local signaling molecules are released by Local signaling molecules are released by some cells; these work only on nearby tissues.some cells; these work only on nearby tissues.

PheromonesPheromones are signaling molecules that have are signaling molecules that have targets outside the body and which are used to targets outside the body and which are used to integrate behaviors.integrate behaviors.


Hormone sources: The endocrine system.Hormone sources: The endocrine system. The sources of hormones (hormone producing The sources of hormones (hormone producing

glands, cells, and organs) may be collectively glands, cells, and organs) may be collectively called the called the endocrine systemendocrine system..

Endocrine sources and the nervous system Endocrine sources and the nervous system function in highly interconnected ways.function in highly interconnected ways.


Hormones often interact.Hormones often interact. In an In an opposing interactionopposing interaction the effect of one the effect of one

hormone opposes the effect of another.hormone opposes the effect of another. In a In a synergistic interactionsynergistic interaction the combined the combined

action of two or more hormones is necessary to action of two or more hormones is necessary to produce the required effect on target cells.produce the required effect on target cells.

In a In a permissive interactionpermissive interaction one hormone one hormone exerts its effect only when a target cell has exerts its effect only when a target cell has been “primed” to respond by another hormone.been “primed” to respond by another hormone.

Animation: Major Human Animation: Major Human Endocrine GlandsEndocrine Glands

CLICKTO PLAY

hypothalamus

pituitary gland

adrenal glands

ovaries

testes

pineal gland

thyroid gland

parathyroid glands

thymus gland

pancreatic islets

Fig. 15.1a, p. 271

Useful References for Section 1Useful References for Section 1


InfoTrac: Review of the Endocrine System. InfoTrac: Review of the Endocrine System. Deirdre G. Bauer. Deirdre G. Bauer. MedSurg NursingMedSurg Nursing, Oct. , Oct. 2005.2005.

Section 2Section 2

Types of Hormones and Types of Hormones and Their SignalsTheir Signals

Types of Hormones and Their Signals Types of Hormones and Their Signals

Hormones come in several chemical forms.Hormones come in several chemical forms. Steroid hormonesSteroid hormones

are lipids made from are lipids made from

cholesterol.cholesterol. Amine hormonesAmine hormones are are

modified amino acids.modified amino acids. Peptide hormonesPeptide hormones are peptides of only a few are peptides of only a few

amino acids.amino acids. Protein hormonesProtein hormones are longer chains of amino are longer chains of amino

acids.acids.


All hormones bind target cells; this signal is All hormones bind target cells; this signal is converted into a form that works in the cell to converted into a form that works in the cell to change activity.change activity.

A target cell’s response to a hormone is A target cell’s response to a hormone is dependent on two factors:dependent on two factors:

• Different hormones activate different cellular Different hormones activate different cellular response mechanisms.response mechanisms.

• Not all cells have receptors for all hormones; the Not all cells have receptors for all hormones; the cells that respond are selected by means of the type cells that respond are selected by means of the type of receptor they possess.of receptor they possess.


Steroid hormones interact with cell DNA.Steroid hormones interact with cell DNA. Steroid hormones, such as estrogen and Steroid hormones, such as estrogen and

testosterone, are lipid-soluble and therefore testosterone, are lipid-soluble and therefore cross plasma membranes readily.cross plasma membranes readily.

• Once inside the cell, they penetrate the nuclear Once inside the cell, they penetrate the nuclear membrane and bind to receptors in the nucleus, membrane and bind to receptors in the nucleus, either turning on or turning off genes.either turning on or turning off genes.

• Switching genes on or off changes the proteins that Switching genes on or off changes the proteins that are made by the cell, thus effecting a response.are made by the cell, thus effecting a response.

Some steroid hormones bind receptors in the Some steroid hormones bind receptors in the cell membrane and change membrane cell membrane and change membrane properties to affect change to the target cell’s properties to affect change to the target cell’s function.function.

receptor

hormone-receptor complexchange in

cell activity

1 A steroid hormonemolecule moves from the blood into the fluid that bathes a target cell.

Fig. 15.2a, p. 273

4 Now the hormone-receptor complex triggers gene activity in the DNA

5 In the cytoplasm, the resulting protein carries out the cell’s response to the hormone signal.

2 Being a lipid-soluable molecule, the steroid hormone diffuses across the target cell’s plasma membrane.

3 The hormone diffuses through the cytoplasm, then on through the nuclear envelope. Inside the nucleus, it will bind with a receptor molecule.

Video: Mechanism of a steroid hormoneVideo: Mechanism of a steroid hormone

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Nonsteroid hormones act indirectly, by way Nonsteroid hormones act indirectly, by way of second messengers.of second messengers.

Nonsteroid hormonesNonsteroid hormones include the amine, include the amine, peptide, and protein hormones.peptide, and protein hormones.

Nonsteroid hormones cannot cross the plasma Nonsteroid hormones cannot cross the plasma membrane of target cells, so they must first membrane of target cells, so they must first bind to a receptor on the plasma membrane.bind to a receptor on the plasma membrane.

• Binding of the hormone to the receptor activates the Binding of the hormone to the receptor activates the receptor; it in turn stimulates the production of a receptor; it in turn stimulates the production of a second messengersecond messenger, a small molecule that can relay , a small molecule that can relay signals in the cell.signals in the cell.

• Cyclic AMPCyclic AMP (cyclic adenosine monophosphate) is (cyclic adenosine monophosphate) is one example of a second messenger.one example of a second messenger.

1 A glucagon molecule diffuses from blood into the fluid that bathes the plasma membrane of a liver cell.

ATP

glucagon receptor at target cell’s membrane

3 The cyclic AMP now activates protein kinase A.

5 Protein kinase A also inhibits an enzyme required for glycogen synthesis.

cyclic AMP + Pi

4 Protein kinase A converts phosphorylasekinase to active form. This enzyme activates a different enzyme, which breaks down glycogen to its glucose monomers.

2 Glucagon binds with the receptor, and the binding activates adenylate cyclase. This enzyme catalyzes the formation of cyclic AMP inside the target cell.

Fig. 15.2b, p. 273

Video: Mechanism of a peptide hormoneVideo: Mechanism of a peptide hormone

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The latest references for topics covered in this section can The latest references for topics covered in this section can be found at the be found at the book companion websitebook companion website. Log in to the . Log in to the book’s e-resources page at book’s e-resources page at www.thomsonedu.comwww.thomsonedu.com to to access InfoTrac articlesaccess InfoTrac articles. .

InfoTrac: Can PYY Cure Obesity? InfoTrac: Can PYY Cure Obesity? U.S. News U.S. News & World Report& World Report, Sept. 15, 2003., Sept. 15, 2003.

Section 3Section 3

The Hypothalamus and The Hypothalamus and Pituitary Gland: Major Pituitary Gland: Major

ControllersControllers

The Hypothalamus and Pituitary GlandThe Hypothalamus and Pituitary Gland

The The hypothalamushypothalamus and and pituitary glandpituitary gland work jointly as the neural-endocrine control work jointly as the neural-endocrine control center.center.

The hypothalamus is a portion of the brain that The hypothalamus is a portion of the brain that monitors internal organs and conditions.monitors internal organs and conditions.

The pituitary is connected to the hypothalamus The pituitary is connected to the hypothalamus by a stalk.by a stalk.

• The The posterior lobeposterior lobe consists of nervous tissue and consists of nervous tissue and releases two hormones made in the hypothalamus.releases two hormones made in the hypothalamus.

• The The anterior lobeanterior lobe makes and secretes hormones makes and secretes hormones that control the activity of other endocrine glands.that control the activity of other endocrine glands.

hypothalamus

pituitary stalk

anterior lobe

posterior lobe

membranearound brain

Fig. 15.1b, p. 271

opticchasma

Location of the pituitary gland:


The posterior pituitary lobe produces ADH The posterior pituitary lobe produces ADH and oxytocin.and oxytocin.

Neurons in the hypothalamus produce Neurons in the hypothalamus produce antidiuretic hormone (antidiuretic hormone (ADHADH) and ) and oxytocinoxytocin, , which are released from axon endings in the which are released from axon endings in the capillary bed of the posterior lobe.capillary bed of the posterior lobe.

ADH (or vasopressin) acts on the walls of ADH (or vasopressin) acts on the walls of kidney tubules to control the body’s water and kidney tubules to control the body’s water and solute levels by stimulating reabsorption.solute levels by stimulating reabsorption.

Oxytocin triggers uterine muscle contractions to Oxytocin triggers uterine muscle contractions to expel the fetus and acts on mammary glands to expel the fetus and acts on mammary glands to release milk.release milk.

Animation: Posterior Pituitary FunctionAnimation: Posterior Pituitary Function

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kidney nephrons mammary

glands

muscles in uterus

wall

ADH oxytocin

Fig. 15.3, p. 274

a Secretory neurons in the hypothalamus synthesize ADH or oxytocin.

b The ADH Oxytocin moves downward inside the axons of the secretory neurons and accumulates in the axon endings.

c Action potentials trigger the release of these hormones, which enter blood capillaries in the posterior lobe of the pituitary.

d The hormone molecules move into the general circulation.


The anterior pituitary lobe produces six The anterior pituitary lobe produces six other hormones.other hormones.

CorticotropinCorticotropin (ACTH) stimulates the adrenal (ACTH) stimulates the adrenal cortex.cortex.

ThyrotropinThyrotropin (TSH) stimulates the thyroid (TSH) stimulates the thyroid gland.gland.

Follicle-stimulating hormoneFollicle-stimulating hormone (FSH) causes (FSH) causes ovarian follicle development and egg ovarian follicle development and egg production.production.


Luteinizing hormoneLuteinizing hormone (LH) also acts on the (LH) also acts on the ovary to release an egg.ovary to release an egg.

ProlactinProlactin (PRL) acts on the mammary glands (PRL) acts on the mammary glands to stimulate and sustain milk production.to stimulate and sustain milk production.

SomatotropinSomatotropin (STH), also known as growth (STH), also known as growth hormone (GH), acts on body cells in general to hormone (GH), acts on body cells in general to promote growth.promote growth.

Most of these hormones are Most of these hormones are releasersreleasers that that stimulate target cells to secrete other stimulate target cells to secrete other hormones; other hormones from the hormones; other hormones from the hypothalamus are hypothalamus are inhibitorsinhibitors and block and block secretions. secretions.

Animation: Anterior Pituitary FunctionAnimation: Anterior Pituitary Function

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Fig. 15.4, p. 275

ACTH TSH FSH LH PRL STH(GH)

adrenal glands thyroid gland

testes in males, ovaries in females

mammary glands

a Cell bodies of different secretory neurons in the hypothalamus secrete releasing and inhibiting hormones.

b The hormones are picked up by a capillary bed at the base of the hypothalamus.

c The bloodstream delivers hormones to a capillary bed in the anterior lobe of pituitary.

d Molecules of the releasing or inhibiting hormone diffuse out of capillaries and act on endocrine cells in the anterior lobe.

e Hormones from anterior lobe cells enter small blood vessels that lead to the general circulation.

most cells(growth-promoting effects)

Video: Hypothalamus and PituitaryVideo: Hypothalamus and Pituitary

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The Pituitary SocietyThe Pituitary Society InfoTrac: The Scent of Trust. InfoTrac: The Scent of Trust. PreventionPrevention, Oct. , Oct.

2005.2005.

Section 4Section 4

Factors That Influence Factors That Influence Hormone EffectsHormone Effects

Problems with control mechanisms can Problems with control mechanisms can result in skewed hormone signals.result in skewed hormone signals.

Endocrine glands in general only release small Endocrine glands in general only release small quantities of hormones and control the quantities of hormones and control the frequency of release to make sure there isn’t frequency of release to make sure there isn’t too much or too little hormone.too much or too little hormone.

Factors That Influence Hormone Effects Factors That Influence Hormone Effects

Abnormal quantities of hormones can lead Abnormal quantities of hormones can lead to growth problems.to growth problems.

GigantismGigantism results from an results from an

oversecretion of growth oversecretion of growth

hormone in childhood.hormone in childhood. Pituitary dwarfismPituitary dwarfism

results from an results from an

undersecretion of GH.undersecretion of GH.


Figures 15.5a and 15.14Figures 15.5a and 15.14

AcromegalyAcromegaly is a is a condition resulting from condition resulting from an oversecretion of GH in an oversecretion of GH in adulthood leading to adulthood leading to abnormal thickening of abnormal thickening of tissues.tissues.

Diabetes insipidusDiabetes insipidus occurs when ADH occurs when ADH secretions fall or stop, secretions fall or stop, leading to dilute urine and leading to dilute urine and the possibility of serious the possibility of serious dehydration.dehydration.


Figure 15.5bFigure 15.5b

Hormone interactions, feedback, and other Hormone interactions, feedback, and other factors also influence a hormone’s effects.factors also influence a hormone’s effects.

At least four factors influence the effects of any At least four factors influence the effects of any given hormone.given hormone.

• Hormones often interact with one another.Hormones often interact with one another.• Negative feedback mechanisms control secretion of Negative feedback mechanisms control secretion of

hormones.hormones.• Target cells may react differently to hormones at Target cells may react differently to hormones at

different times.different times.• Environmental cues can affect release of hormones.Environmental cues can affect release of hormones.

Hormones throughout the body are affected in Hormones throughout the body are affected in similar ways.similar ways.


Video: Hormone Replacement TherapyVideo: Hormone Replacement Therapy

This video clip is available in CNN Today This video clip is available in CNN Today Videos for Anatomy & Physiology, 2003, Videos for Anatomy & Physiology, 2003, Volume VII. Instructors, contact your local Volume VII. Instructors, contact your local sales representative to order this volume, sales representative to order this volume, while supplies last.while supplies last.



InfoTrac: AcromegalyInfoTrac: Acromegaly. Ana Pokrajac-Ana Pokrajac-Simeunovic and Peter Trainer. Simeunovic and Peter Trainer. Chemist & Chemist & DruggistDruggist, Nov. 19, 2005., Nov. 19, 2005.

Section 5Section 5

The Thymus, Thyroid, The Thymus, Thyroid, and Parathyroid Glandsand Parathyroid Glands

Thymus gland hormones aid immunity.Thymus gland hormones aid immunity. Thyroid hormones affect metabolism, Thyroid hormones affect metabolism,

growth, and development.growth, and development. The The thyroid glandthyroid gland secretes secretes thyroid hormonethyroid hormone

(TH), which has effects on metabolism, growth, (TH), which has effects on metabolism, growth, and development; the thyroid gland also and development; the thyroid gland also secretes secretes calcitonincalcitonin, which helps regulate , which helps regulate calcium levels in the blood.calcium levels in the blood.


Fig. 15.6a, p. 278

thyroid cartilage (Adam’sapple)

blood vessel

thyroidgland

trachea(windpipe)

Animation: Thyroid Hormone ActionAnimation: Thyroid Hormone Action

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Fig. 15.6b, p. 278

StimulusBlood level of thyroidhormone falls below a set point.

Hypothalamus

Anterior Pituitary

Thyroid Gland

Rise in the blood level of thyroid hormone inhibits secretion of TRH and THS.

Thyroid hormoneis secreted.

+

TRH

TSH

Response

Fig. 15.6b, p. 278

StimulusBlood level of thyroidhormone falls below a set point.

Stepped Art

TRH

TSH

Thyroid hormoneis secreted.

Thyroid Gland

+Hypothalamus

Anterior Pituitary

Response–

–

Rise in the blood level of thyroid hormone inhibits secretion of TRH and TSH.

Iodine-deficient diets interfere with proper Iodine-deficient diets interfere with proper synthesis of thyroid hormones.synthesis of thyroid hormones.

• Simple goiterSimple goiter is an enlargement is an enlargement

of one or both lobes of the thyroid of one or both lobes of the thyroid

gland in the neck; enlargement gland in the neck; enlargement

follows low blood levels of thyroid follows low blood levels of thyroid

hormones (hormones (hypothyroidismhypothyroidism).).• Graves diseaseGraves disease and other forms of and other forms of

hyperthyroidismhyperthyroidism result from too result from too

much thyroid hormone in the blood.much thyroid hormone in the blood.

Figure 15.7Figure 15.7


PTH from the parathyroids is the main PTH from the parathyroids is the main calcium regulator.calcium regulator.

Humans have four Humans have four parathyroid parathyroid glandsglands,, which secrete which secrete parathyroid hormoneparathyroid hormone (PTH), (PTH), the main regulator of blood the main regulator of blood calcium levels.calcium levels.

• More PTH is secreted when blood calcium levels More PTH is secreted when blood calcium levels drop below a certain point; less is secreted when drop below a certain point; less is secreted when calcium rises.calcium rises.

• Calcitonin contributes to processes that pull calcium Calcitonin contributes to processes that pull calcium out of the blood.out of the blood.


Fig. 15.8, p. 279

Decrease in calcium ionconcentration in blood

Parathyroidglands

PTH

stimulatesCalcium ion

level increases

Osteoclastsreleasecalcium ionsfrom bone

Kidney tubulesincreasecalcium ionreabsorption

Intestineincreasescalcium ionabsorption

Fig. 15.8, p. 279

Decrease in calcium ionconcentration in blood

Osteoclastsreleasecalcium ionsfrom bone

Kidney tubulesIncrease calcium ion reabsorption

IntestineIncreases calcium ion absorption Stepped Art

Parathyroidglands

PTH

stimulatesCalcium ion

level increases

RicketsRickets in children arises from a vitamin D in children arises from a vitamin D deficient diet; vitamin D is needed to aid deficient diet; vitamin D is needed to aid absorption of calcium from food.absorption of calcium from food.

HyperparathyroidismHyperparathyroidism sees so much calcium sees so much calcium being withdrawn from a person’s bones that the being withdrawn from a person’s bones that the bone tissue is dangerously weakened.bone tissue is dangerously weakened.




The American Thyroid AssociationThe American Thyroid Association InfoTrac: Primary Hyperparathyroidism (The InfoTrac: Primary Hyperparathyroidism (The

Effective Physician). William E. Golden; Effective Physician). William E. Golden; Robert H. HopkinsRobert H. Hopkins. Internal Medicine News. Internal Medicine News, , Dec. 1, 2005.Dec. 1, 2005.

Section 6Section 6

Adrenal Glands and Adrenal Glands and Stress ResponsesStress Responses

Adrenal Glands and Stress ResponsesAdrenal Glands and Stress Responses

The adrenal cortex produces The adrenal cortex produces glucocorticoids and mineralocorticoids.glucocorticoids and mineralocorticoids.

One One adrenal glandadrenal gland is located on top of each is located on top of each kidney; the outer part of each gland is the kidney; the outer part of each gland is the adrenal cortexadrenal cortex, the site of production for two , the site of production for two major steroid hormones.major steroid hormones.


GlucocorticoidsGlucocorticoids raise the level of glucose in raise the level of glucose in the blood.the blood.

• The main glucocorticoid, The main glucocorticoid, cortisolcortisol, is secreted when , is secreted when the body is stressed and blood sugar levels drop; the body is stressed and blood sugar levels drop; cortisol promotes cortisol promotes gluconeogenesisgluconeogenesis, a mechanism , a mechanism for making glucose from amino acids derived from for making glucose from amino acids derived from protein breakdown.protein breakdown.

• Cortisol also dampens the uptake of glucose from Cortisol also dampens the uptake of glucose from the blood, stimulates the breakdown of fats for the blood, stimulates the breakdown of fats for energy, and suppresses inflammation.energy, and suppresses inflammation.

• HypoglycemiaHypoglycemia can result when the adrenal cortex can result when the adrenal cortex makes too little cortisol; this results in chronically low makes too little cortisol; this results in chronically low glucose levels in the blood.glucose levels in the blood.

Animation: Control of Cortisol SecretionAnimation: Control of Cortisol Secretion

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Hypothalamus

Anterior Pituitary

Adrenal Cortex

CRH

ACTH

Cortisol is secreted, with these effects:

a Blood level of cortisol falls below a set point

adrenal cortex

adrenal medulla

kidney

c Cell uptake of glucose from blood slows in many tissues, especially muscles (not the brain).

d Proteins are broken down in many tissues, muscles especially. The amino acids are converted to glucose, and used in the assembly or repair of cell structures. e Fats in adipose tissue are broken down to fatty acids that enter blood as an alternative energy source, indirectly conserving glucose for the brain.

Fig. 15.9, p. 281

Response

b

f Both thehypothalamusand pituitarydetect rise in blood level of cortisol and slow its secretion.

Stimulus


MineralocorticoidsMineralocorticoids regulate the concentrations regulate the concentrations of minerals such as Kof minerals such as K++ and Na and Na++ in the in the extracellular fluid; aldosterone is one example extracellular fluid; aldosterone is one example that works in the nephrons of the kidneys.that works in the nephrons of the kidneys.

The adrenal cortex also secretes sex hormones The adrenal cortex also secretes sex hormones in the fetus and at puberty.in the fetus and at puberty.


Hormones from the adrenal medulla help Hormones from the adrenal medulla help regulate blood circulation.regulate blood circulation.

The inner part of the adrenal gland, the The inner part of the adrenal gland, the adrenal adrenal medullamedulla, secretes epinephrine and , secretes epinephrine and norepinephrine.norepinephrine.

Secretion by the adrenal medulla influences Secretion by the adrenal medulla influences these molecules to behave like hormones to these molecules to behave like hormones to regulate blood circulation and carbohydrate use regulate blood circulation and carbohydrate use during stress. during stress.


Long-term stress can damage health.Long-term stress can damage health. Stress triggers the fight-flight response and the Stress triggers the fight-flight response and the

release of cortisol, epinephrine, and release of cortisol, epinephrine, and norepinephrine; constant release of these norepinephrine; constant release of these molecules can contribute to hypertension and molecules can contribute to hypertension and cardiovascular disease.cardiovascular disease.

Excess cortisol suppresses the immune Excess cortisol suppresses the immune system, making individuals susceptible to system, making individuals susceptible to disease.disease.

Social connections for support and exercise for Social connections for support and exercise for health can reduce the effects of stress.health can reduce the effects of stress.

Video: Peanut AllergiesVideo: Peanut Allergies

This video clip is available in CNN Today This video clip is available in CNN Today Videos for Anatomy & Physiology, 2004, Videos for Anatomy & Physiology, 2004, Volume VIII. Instructors, contact your local Volume VIII. Instructors, contact your local sales representative to order this volume, sales representative to order this volume, while supplies last.while supplies last.



InfoTrac: Prenatal Exposure to Stress and InfoTrac: Prenatal Exposure to Stress and Stress Hormones Influences Child Stress Hormones Influences Child Development. Elysia Poggi Davis; Curt A. Development. Elysia Poggi Davis; Curt A. SandmanSandman. Infants & Young Children. Infants & Young Children, July–, July–Sept. 2006.Sept. 2006.

Section 7Section 7

The Pancreas: The Pancreas: Regulating Blood SugarRegulating Blood Sugar

The Pancreas: Regulating Blood SugarThe Pancreas: Regulating Blood Sugar

The pancreas has both exocrine and The pancreas has both exocrine and endocrine functions; the endocrine cells are endocrine functions; the endocrine cells are located in clusters called located in clusters called pancreatic isletspancreatic islets. .

Fig. 15.10, p. 282

stomach

pancreas

small intestine

The Pancreas: Regulating Blood SugarThe Pancreas: Regulating Blood Sugar

Each pancreatic islet secretes three Each pancreatic islet secretes three hormones:hormones:

• Alpha cellsAlpha cells secrete secrete glucagonglucagon, which causes , which causes glycogen stored in the liver to be converted to glycogen stored in the liver to be converted to glucose, which then enters the bloodstream.glucose, which then enters the bloodstream.

• Beta cellsBeta cells secrete secrete insulininsulin, which stimulates the , which stimulates the uptake of glucose by liver, muscle, and adipose cells uptake of glucose by liver, muscle, and adipose cells to reduce levels in the blood, especially after a meal.to reduce levels in the blood, especially after a meal.

• Delta cellsDelta cells secrete secrete somatostatinsomatostatin, which can inhibit , which can inhibit the secretion of glucagon and insulin.the secretion of glucagon and insulin.


Animation: Hormones and Animation: Hormones and Glucose MetabolismGlucose Metabolism

CLICKTO PLAY

Fig. 15.10a, p. 282

StimulusIncrease in blood glucose

Stimulus Decrease in blood

glucose

Body cells, especially in muscle and adipose tissue, take up and use more glucose.Cells in skeletal muscle and liver store glucose in the form of glycogen.

ResponseDecrease in blood glucose

ResponseIncrease in blood glucose

Cells in liver breakdown glycogen faster.The released glucosemolecules enter blood.

glucagon insulin

beta cellsalpha cells

PANCREAS

glucagon insulin

beta cellsalpha cells

a

e

f

b c g h

i

j

+_x

d

_+ x


The latest references for topics covered in this section can The latest references for topics covered in this section can be found at the be found at the book companion websitebook companion website. Log in to the . Log in to the book’s e-resources page at book’s e-resources page at www.thomsonedu.comwww.thomsonedu.com to to access InfoTrac articlesaccess InfoTrac articles..

Journal of the PancreasJournal of the Pancreas InfoTrac: Perfecting a ‘Pancreas’: Scientists InfoTrac: Perfecting a ‘Pancreas’: Scientists

Fine-Tune a Device to Be Used by Diabetics. Fine-Tune a Device to Be Used by Diabetics. Jamie Talan. Jamie Talan. Newsday, Newsday, May 15, 2006.May 15, 2006.

Section 8Section 8

Disorders of Glucose Disorders of Glucose HomeostasisHomeostasis

Disorders of Glucose Homeostasis Disorders of Glucose Homeostasis

Diabetes mellitusDiabetes mellitus is a is a

disease resulting from the disease resulting from the

secretion of too little insulin.secretion of too little insulin. Without insulin, cells can’t Without insulin, cells can’t

remove glucose from the remove glucose from the

blood; the kidneys remove the excess in urine, blood; the kidneys remove the excess in urine, creating imbalances in water-solute creating imbalances in water-solute concentrations.concentrations.

Metabolic acidosisMetabolic acidosis, a lower than optimal blood , a lower than optimal blood pH, can result because of this imbalance.pH, can result because of this imbalance.



In In type 1 diabetestype 1 diabetes (also known as (also known as “juvenile-onset diabetes”) the insulin is no “juvenile-onset diabetes”) the insulin is no longer produced because the beta cells longer produced because the beta cells have been destroyed by an autoimmune have been destroyed by an autoimmune response.response.

Only about 1 in 10 diabetics have this form of Only about 1 in 10 diabetics have this form of diabetes.diabetes.

Treatment is by insulin injection.Treatment is by insulin injection.


Type 2 diabetes is a global health crisis.Type 2 diabetes is a global health crisis. In In type 2 diabetestype 2 diabetes the insulin levels are near the insulin levels are near

normal but the target cells cannot respond to normal but the target cells cannot respond to the hormone.the hormone.

• Beta cells eventually break down and produce less Beta cells eventually break down and produce less and less insulin.and less insulin.

• Excess glucose in the blood damages capillaries.Excess glucose in the blood damages capillaries. Cardiovascular disease, stroke, heart attack, Cardiovascular disease, stroke, heart attack,

and other serious complications arise.and other serious complications arise.


Metabolic syndrome is a warning sign.Metabolic syndrome is a warning sign. PrediabetesPrediabetes describes individuals with slightly describes individuals with slightly

elevated blood sugar levels that have an elevated blood sugar levels that have an increased risk for developing type 2 diabetes; increased risk for developing type 2 diabetes; about 20 million Americans fall into this about 20 million Americans fall into this category and do not know it.category and do not know it.


A composite of features collectively called A composite of features collectively called metabolic syndromemetabolic syndrome also describe risk for also describe risk for diabetes; these features include: “apple diabetes; these features include: “apple shaped” waistline, elevated blood pressure, low shaped” waistline, elevated blood pressure, low levels of HDL, and elevated glucose and levels of HDL, and elevated glucose and triglycerides.triglycerides.

Type 2 diabetes can be controlled with a Type 2 diabetes can be controlled with a combination of improved diet, exercise, and combination of improved diet, exercise, and sometimes drugs.sometimes drugs.

Video: Gene Therapy for DiabetesVideo: Gene Therapy for Diabetes

This video clip is available in CNN Today This video clip is available in CNN Today Videos for Genetics, 2005, Volume VII. Videos for Genetics, 2005, Volume VII. Instructors, contact your local sales Instructors, contact your local sales representative to order this volume, while representative to order this volume, while supplies last.supplies last.



American Diabetes AssociationAmerican Diabetes Association CDC: DiabetesCDC: Diabetes InfoTrac: Pancreas and Islet Transplantation InfoTrac: Pancreas and Islet Transplantation

in Type 1 Diabetes. in Type 1 Diabetes. Diabetes CareDiabetes Care, April , April 2006.2006.

InfoTrac: Preventing Diabetes. Kathy InfoTrac: Preventing Diabetes. Kathy Doheny. Doheny. Natural Health, Natural Health, April 2004.April 2004.

Section 9Section 9

Some Final Examples of Some Final Examples of Integration and ControlIntegration and Control

Light/dark cycles influence the pineal gland, Light/dark cycles influence the pineal gland, which produces melatonin.which produces melatonin.

Located in the brain, the Located in the brain, the pineal glandpineal gland is a is a modification of a primitive “third eye” and is modification of a primitive “third eye” and is sensitive to light and seasonal influences; this sensitive to light and seasonal influences; this gland secretes the hormone gland secretes the hormone melatoninmelatonin..

• Melatonin is secreted in the dark, and levels change Melatonin is secreted in the dark, and levels change with the seasons.with the seasons.

• The The biological clockbiological clock seems to tick in synchrony seems to tick in synchrony with day length and is apparently influenced by with day length and is apparently influenced by melatonin.melatonin.

Some Final Examples ofSome Final Examples ofIntegration and ControlIntegration and Control

Seasonal affective disorderSeasonal affective disorder (SAD) affects persons during (SAD) affects persons during the winter and may result the winter and may result from an out-of-sync biological from an out-of-sync biological clock; melatonin makes it clock; melatonin makes it worse; exposure to intense worse; exposure to intense light helps.light helps.

Melatonin levels may Melatonin levels may potentially be linked to the potentially be linked to the onset of puberty.onset of puberty.


Hormones also are produced in the heart Hormones also are produced in the heart and GI tract.and GI tract.

Atrial natriuretic peptideAtrial natriuretic peptide (ANP) produced by (ANP) produced by the heart atria regulates blood pressure.the heart atria regulates blood pressure.

Gastrin and secretin from the GI tract stimulate Gastrin and secretin from the GI tract stimulate release of stomach and intestinal secretions.release of stomach and intestinal secretions.


Prostaglandins have many effects.Prostaglandins have many effects. More than 16 More than 16 prostaglandinsprostaglandins have been have been

identified in tissues throughout the body.identified in tissues throughout the body.• When stimulated by epinephrine and norepinephrine, When stimulated by epinephrine and norepinephrine,

prostaglandins cause smooth muscles in blood prostaglandins cause smooth muscles in blood vessels to constrict or dilate.vessels to constrict or dilate.

• Allergic responses to dust and pollen may be Allergic responses to dust and pollen may be aggravated by the effects of prostaglandins on aggravated by the effects of prostaglandins on airways in the lungs.airways in the lungs.

Prostaglandins have major effects on Prostaglandins have major effects on menstruation and childbirth.menstruation and childbirth.


Some Final Examples of Some Final Examples of Integration and Control Integration and Control

Growth factors influence cell division.Growth factors influence cell division. Hormonelike proteins called Hormonelike proteins called growth factorsgrowth factors

influence growth by regulating the rate of influence growth by regulating the rate of cellular division.cellular division.

• Epidermal growth factorEpidermal growth factor (EGF) influences the growth (EGF) influences the growth of many cell types, as does of many cell types, as does insulinlike growth factorinsulinlike growth factor (IGF). (IGF).

• Nerve growth factorNerve growth factor (NGF) (NGF) promotes growth and survival promotes growth and survival of neurons in the developing of neurons in the developing embryo.embryo.


The current list of growth factors is expanding The current list of growth factors is expanding rapidly; many of these factors may have rapidly; many of these factors may have applications in medicine.applications in medicine.

Pheromones may be important Pheromones may be important communication molecules in humans.communication molecules in humans.

Pheromones are released outside of the body Pheromones are released outside of the body by several animals to serve as sex attractants, by several animals to serve as sex attractants, territory markers, and communication signals.territory markers, and communication signals.

Recent studies suggest that humans also may Recent studies suggest that humans also may communicate using pheromones.communicate using pheromones.


Are endocrine disrupters at work?Are endocrine disrupters at work? Endocrine disrupters are proposed to be Endocrine disrupters are proposed to be

environmental substances that interfere with environmental substances that interfere with reproduction or development.reproduction or development.

Sperm counts in Sperm counts in males in Western males in Western countries declined countries declined about 40% between about 40% between the years 1938 and the years 1938 and 1990, possibly due 1990, possibly due to exposure to estrogens in the environment.to exposure to estrogens in the environment.




National Research Center for Women & Families: National Research Center for Women & Families: Are Pretty Products Causing Early Puberty?Are Pretty Products Causing Early Puberty?

Howard Hughes Medical Institute: The Matters: Howard Hughes Medical Institute: The Matters: Biological ClockworksBiological Clockworks

InfoTrac: Drug of Darkness: Can a Pineal Hormone InfoTrac: Drug of Darkness: Can a Pineal Hormone Head Off Everything from Breast Cancer to Aging? Head Off Everything from Breast Cancer to Aging? Science NewsScience News, May 13, 1995., May 13, 1995.

InfoTrac: The Chemistry of Love. Sanjay Gupta. InfoTrac: The Chemistry of Love. Sanjay Gupta. TimeTime, Feb. 18, 2002., Feb. 18, 2002.

Video: Hormone-Induced AdjustmentsVideo: Hormone-Induced Adjustments

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