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Anatomy and Physiology, Seventh Edition

Rod R. Seeley

Idaho State University

Trent D. Stephens


Philip Tate

Phoenix College

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

*See PowerPoint Image Slides for all figures and tables pre-inserted into PowerPoint without notes.

Chapter 17

Lecture Outline*

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Chapter 17

Functional Organization of

Endocrine System

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General Characteristics Glands that secrete chemical

signals (hormones) intocirculatory system

Hormone characteristics

Produced in small quantities

Secreted into intercellularspace

Transported some distancein circulatory system

Acts on target tissueselsewhere in body

Regulate activities of body

structures Ligands: more general term for

chemical signals

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Regulation of

Activities:

Comparison of

Endocrine andNervous Systems

Endocrine: amplitude modulated signals.

Amount of hormone determines strengthof signal

Onset within minutes of secretion ofhormone

Nervous: frequency-modulated signals.

Frequency of action potentials producedby neurons determines strength of signal.

Onset within milliseconds

Two systems actually inseparable

Nervous system secretesneurohormones into circulatory system

Nervous system uses neurotransmittersand neuromodulators as ligands

Some parts of endocrine systeminnervated directly by nervous system

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Intercellular Chemical Signals

Hormones: type of intercellular signal. Produced by cells

of endocrine glands, enter circulatory system, and affectdistant cells; e.g., estrogen

Autocrine: released by cells and have a local effect onsame cell type from which chemical signals released; e.g.,

prostaglandin

Paracrine: released by cells and affect other cell typeslocally without being transported in blood; e.g.,somatostatin

Pheromones: secreted into environment and modifybehavior and physiology; e.g., sex pheromones

Neurohormone: produced by neurons and function likehormones; e.g., oxytocin

Neurotransmitter orneuromodulator: produced byneurons and secreted into extracellular spaces by

presynaptic nerve terminals; travels short distances;

influences postsynaptic cells; e.g., acetylcholine.

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Control of Secretion Rate

Most hormones controlled by negative feedbacksystems

Most hormones are not secreted at constant rate,

but their secretion is regulated by three differentmethods

1. The action of a substance other than a hormone on anendocrine gland.

2. Neural control of endocrine gland.3. Control of secretory activity of one endocrine gland

by hormone or neurohormone secreted by anotherendocrine gland

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1. Humoral stimulus: Action of Substance

Other Than Hormone An increased blood glucose

concentration stimulatesincreased insulin secretion fromthe pancreas

Insulin increases glucose uptakeby tissues, which decreasesblood glucose levels.

Autonomic nervous system alsoinfluences insulin secretion

Hypocalcemia stimulates PTHsecretion from parathyroids

Hypersecretion stimulatescalcitonin from parafollicularcells

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2. Nervous System Regulation

Stimuli such as stress orexercise activate thesympathetic division of theautonomic nervous system

Sympathetic neurons stimulate

the release of epinephrine andsmaller amounts ofnorepinephrine from the adrenalmedulla. Epinephrine andnorepinephrine prepare thebody to respond to stressfulconditions.

Once the stressful stimuli areremoved, less epinephrine isreleased as a result of decreasedstimulation from the autonomicnervous system.

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3. Hormonal Regulation

Secretion of tropichomones from hypotha-

lamus stimulates secre-

tion of anterior pituitary

homrones.

Example shows TRH

(thyrotropic releasing

hormone) from hypotha-

lamus stimulating secre-

tion of TSH from anteriorpituitary.

Note: TSH itself is a

tropic hormone in that it

stimulates T3/T4 secretion.

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Positive and Negative Feedback

POSITIVE

During the menstrual cycle, beforeovulation, small amounts ofestrogen are secreted from theovary.

Estrogen stimulates the release ofgonadotropin-releasing hormone

(GnRH) from the hypothalamusand luteinizing hormone (LH)from the anterior pituitary

GnRH also stimulates the releaseof LH from the anterior pituitary

LH causes the release of additional

estrogen from the ovary. TheGnRH and LH levels in the bloodincrease because of this positive-feedback effect.

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Positive and Negative Feedback

NEGATIVE

During the menstrual cycle,after ovulation, the ovarybegins to secreteprogesterone in response toLH.

Progesterone inhibits therelease of GnRH from thehypothalamus and LH fromthe anterior pituitary.

Decreased GnRH releasefrom the hypothalamus

reduces LH secretion fromthe anterior pituitary. GnRHand LH levels in the blooddecrease because of thisnegative-feedback effect.

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Changes in Hormone Secretion

Through Time

a) Chronic hormone regulation.Maintenance of relativelyconstant concentration ofhormone. Thyroid hormone.

b) Acute hormone regulation.Epinephrine in response tostress.

c) Cyclic hormone regulation.Female reproductive

hormones.

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Transport and

Distribution Hormones dissolve in blood plasma andare transported in free form or arereversibly bound to plasma proteins

Free form can diffuse from plasma intointerstitial fluid and affect cells

As concentration of free hormonemolecules increase, more hormonesmolecules diffuse from capillaries intointerstitial spaces to bind to target cells

Lipid soluble hormones diffuse throughcapillary cells. Water soluble hormonesdiffuse through pores in capillaries calledfenestrae.

A large decrease in plasma proteinconcentration can result in loss of a

hormone from the blood because freehormones are rapidly eliminated fromcirculation through kidney or liver

Hormones are distributed quickly becausethey circulate in the blood

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Metabolism and Excretion

Half-life: The length oftime it takes for half adose of substance to beeliminated fromcirculatory system

Long half-life: regulate

activities that remain ata constant rate throughtime. Usually lipidsoluble and travel inplasma attached toproteins

Short half-life: water-soluble hormones asproteins, epinephrine,norepinephrine. Have arapid onset and shortduration

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Hormone (Ligand) Interaction with Target

Tissues

Portion of molecule where ligandbinds is called binding site.

If the molecule is a receptor (like ina cell membrane) the binding site iscalled a receptor site

Ligand/receptor site is specific; e.g.,epinephrine cannot bind to thereceptor site for insulin.

The purpose of binding to targettissue is to elicit a response by thetarget cell.

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Down-

Regulation

Normally, receptor molecules aredegraded and replaced on aregular basis.

Down-regulation Rate at which receptors are

synthesized decreases in some cellsafter the cells are exposed to aligand.

Combination of ligands andreceptors can increase the rate at

which receptor molecules aredegraded. This combined form istaken into the cell by phagocytosisand then broken down.

Tissues that exhibit down-regulation are adapted to short-term increases in hormoneconcentration.

Tissues that respond to hormonesmaintained at constant levelsnormally do not exhibit down-

regulation.

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Up-Regulation

Some stimulus causes increasein synthesis of receptors for ahormone, thus increasessensitivity to that hormone

For example, FSH stimulationof the ovary causes an increaseof LH receptors. Ovarian cellsare now more sensitive to LH,even if the concentration of LHdoes not change. This causes

ovulation.

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Membrane-Bound Receptors

Receptor: integral proteins with

receptor site at extracellular surface.Interact with ligands that cannot passthrough the plasma membrane.

Ligands

Water-soluble or large-molecular-

weight hormones. Attachment ofligand causes intracellular reaction.

Large proteins, glycoproteins,polypeptides; smaller moleculeslike epinephrine andnorepinephrine

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Intracellular Receptors

Receptors: in the cytoplasm or

in the nucleus Ligands

Lipid soluble andrelatively small molecules;

pass through the plasma

membrane. React either with enzymesin the cytoplasm or withDNA to causetranscription andtranslation

Thyroid hormones,testosterone, estrogen,

progesterone, aldosterone,and cortisol

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Membrane-Bound Receptors

Proteins or glycoproteins that have polypeptide chainsfolded to cross cell membrane several times

Ligand binds reversibly to receptor site on receptorprotein

Three different results of ligand binding

1. Alteration of membrane permeability. Example:acetylcholine

2. Activation of G proteins associated with themembrane, causes production of intracellular mediatorsuch as cyclicAMP, leads to activation of intracellularenzymes. Example: LH

3. Receptors linked to intracellular enzymes throughintracellular mediators. Mediators alter activity ofintracellular enzymes. Examples: nitric oxide,cyclicGMP, Ca ions.

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Intracellular Receptors

Proteins in cytoplasm or nucleus

Hormones bind with intracellular receptor andreceptor-hormone complex activate certain genes,causes transcription of mRNA and translation.These proteins (enzymes) produce the response of

the target cell to the hormone Latent period of several hours because time is

required to produce mRNA and protein

Processes limited by breakdown of receptor-

hormone complex Estrogen and testosterone produce different

proteins in cells that cause the differing secondarysexual characteristics of females and males.

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Anatomy and Physiology, Seventh Edition

Rod R. Seeley


Trent D. Stephens


Philip Tate

Phoenix College

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

*See PowerPoint Image Slides for all figures and tables pre-inserted into PowerPoint without notes.

Chapter 18

Lecture Outline*

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Endocrine System Functions

Metabolism and tissue maturation

Ion regulation

Water balance Immune system regulation

Heart rate and blood pressure regulation

Control of blood glucose and other nutrients

Control of reproductive functions Uterine contractions and milk release

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Pituitary Gland and

Hypothalamus Where nervous and

endocrine systems interact

Hypothalamus regulatessecretions of anterior

pituitary Posterior pituitary is an

extension of thehypothalamus

Anterior pituitary produces

nine major hormones that Regulate body functions

Regulate the secretions ofother endocrine glands

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Pituitary Gland Structure

Posterior pituitary(neurohypophysis): extension

of the nervous system via the

infundibulum

Secretes neurohormones

Anterior pituitary(adenohypophysis)

Consists of three areas with

indistinct boundaries: pars

distalis, pars intermedia, pars

tuberalis

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Hypothalamus, Anterior Pituitary, and Target Tissues

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Releasing and Inhibiting Hormones

Tropins ortropic hormones: hormones that regulate the hormone secretionsof target endocrine tissues. All anterior pituitary hormones are tropins.

Releasing hormones secreted by the hypothalamus: GHRH. Growth hormone-releasing hormone. Causes the anterior

pituitary to release growth hormone.

TRH. Thyroid-releasing hormone. Causes the anterior pituitary torelease thyroid-stimulating hormone (TSH).

CRH. Corticotropin-releasing hormone. Causes anterior pituitary to

produce adrenocorticotropic hormone (ACTH) GnRH. Gonadotropin-releasing hormone. Causes anterior pituitary toproduce FSH (follicle stimulating hormone) and LH (luteinizinghormone).

PRH. Prolactin-releasing hormone. Causes the anterior pituitary torelease prolactin.

Inhibiting hormones:

GHIH. Growth hormone-inhibiting hormone, somatostatin. Causesthe anterior pituitary to decrease release of growth hormone.

PIH. Prolactin-inhibiting hormone. Causes the anterior pituitary todecrease release of prolactin.

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Hypothalamus, Posterior Pituitary and Target

Tissues

Hypothalamic neurons

syntheisze ADH and

oxytocin.

Latter hormones travel

to post. pituitary via

axons of hypothalamic

neurons.

ADH and oxytocin

enter circulation in post.pituitary.

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Hormones of Posterior Pituitary: ADH

Antidiuretic hormone (ADH). Also called vasopressin.

A. Osmoreceptors (specialized neurons of

hypothalamus monitor changes in intercellular

osmolality (relative concentrations of electrolytes and

water). If the concentration of electrolytes increases

or if the concentration of water decreases, then ADHsecretion is stimulated.

B. Baroreceptors (specialized neurons found in walls of

atria of heart, large veins, carotid arteries, aortic arch)

sense changes in blood pressure (BP). If BPdecreases, then ADH secretion is stimulated.

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Control of ADH Secretion

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Control of Oxytocin Secretion

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Anterior Pituitary Hormones

Growth hormone (GH) or somatotropin

Thyroid-stimulating hormone (TSH)

Adrenocorticotropic hormone (ACTH)

Melanocyte-stimulating hormone(MSH)

Beta endorphins

Lipotropins

Luteinizing hormone (LH)

Follicle-stimulating hormone (FSH)

Prolactin

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Growth Hormone (GH or somatotropin)

Stimulates uptake of amino acids; proteinsynthesis; growth in most tissues.

Stimulates breakdown of fats to be used as

an energy source but stimulates synthesis ofglycogen: glucose sparing

Promotes bone and cartilage growth

Regulates blood levels of nutrients after ameal and during periods of fasting

Stimulates glucose synthesis by liver

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Figure 16.6

Metabolic Action of Growth

Hormone

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Growth Hormone Stimulation:functions in

regulating growth, tissue maintenance, metabolismGHRHfrom hypothalamus causes release of

Growth hormonefrom anterior pituitary effects

Target tissues: most tissues of the body

Direct effect: GH binds to receptors on cells and causeschanges within the cells. Increased lipolysis and decreaseduse of glucose for energy

Indirect effect: causes liver and skeletal muscle to produce

somatomedins; e.g., insulinlike growth factors (IGFs) Insulinlike growth factors: bind to receptors on

membranes of target cells. Stimulate growth incartilage, bone; increased synthesis of proteins inskeletal muscle.

l i f G S i

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Regulation of GH Secretion1. Stress and decreased glucose

levels increase release of GHRH

and decrease release of GHIH.

2. GHRH and GHIN travel via

thehypothalamohypophyseal

portal system to ant. pituitary

3. Increased GHRH and reduced

GHIH act on AP and result inincreased GH secretion.

4. GH acts on target tissues.

5. Increasing GH levels have neg

feedback effect on hypothala.

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Growth Hormone: Inhibition

Hypothalamus produces growth hormone inhibitinghormone (GHIH = somatostatin)

Inhibits production of GH by anterior pituitary.

GHRH secretion in response to low blood glucose, stress,increase in certain a.a.

GHIH secretions in response to high blood glucose.

Peak GH levels during deep sleep; levels lower at other

times of day. Hyposecretion of GH may result in dwarfism

Hypersecretion may result ingiantism oracromegaly de-

pending on ossification of epiphyseal plates

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TSH and Thyroid Hormones

TRH from hypothalamus causes the release

ofTSHfrom anterior pituitary which

causes secretion and storage of hormonesT3 and T4 from and within the thyroid gland

TSH increases activity of phospholipasethat opens Ca2+ channels, increasing Ca2+concentration in cells of the thyroid gland

T3 and T4 inhibit TRH and TSH secretion

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Adrenocorticotrophic Hormone (ACTH)

CRH from hypothalamus causes release of

ACTH from anterior pituitary which

Causes cortisol secretion from the adrenalcortex (a glucocorticoid from the zonafasciculata)

Causes aldosterone secretion from theadrenal cortex (a mineralocorticoid from

the zona glomerulosa) Binds directly to melanocytes of the skin;

causes increase in production of melanin.

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Melanocyte Stimulating Hormone,

Endorphins, and Lipotropins ACTH, MSH, endorphins and lipotropins all derived

from the same large precursor molecule when stimulated

by CRH

MSH causes melanocytes to produce more melanin

Endorphins act as an analgesic; produced during times of

stress.

Lipotropins cause adipose cells to catabolize fat

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Th id

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Thyroid

Gland One of largest endocrine glands; Highly

vascular. Iodine enters follicular cells by activetransport. Only gland that stores hormone.

Histology Composed offollicles: follicular cells

surrounding thyroglobulin/thyroidhormones

Parafollicular cells: between follicles

Physiology

Follicular cells secrete thyroglobulin intolumen of follicle. Iodine and a.a. tyrosinenecessary for production of T3 and T4.Hormones stored here attached to thethyroglobulin then absorbed into follicular

cells; hormones disattached fromthyroglobulin and released into circulation.

Parafollicular cells. Secrete calcitoninwhich reduces [Ca2+] in body fluids whenCa levels are elevated.

Bi th i f Th id

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Biosynthesis of Thyroid

Hormones

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Thyroid Hormones Produced by follicular cells

Triiodothyronine orT3-less produced Tetraiodothyronine orT4 orthyroxine-more

99.6% of thyroxine in the blood is bound to thyroxine-binding globulin (TBG) from the liver. Rest is free.

TBG has a higher affinity for T4 than for T3; amt of freeunbound T3 in plasma is 10xs greater than free T4.

Only free thyroxine and T3 can enter cells; bound-thyroxine serves as a reservoir of this hormone

33-40% of T4 converted to T3 in cells: T3 more potent

Bind with intracellular receptormolecules and initiatenew protein synthesis

Increase rate of glucose, fat, protein metabolism inmany tissues thus increasing body temperature

Normal growth of many tissues dependent on presence

of thyroid hormones.

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Effects of T3 and T4

1. Maintain normal rate of metabolism.

2. Increase the rate at which glucose, fat, and protein are meta-bolized.

3. Increase the activity of Na+-K+ pump which increases body

temperature.

4. Can alter the number and activity of mitochondria resulting in

greater ATP synthesis and heat production.

5. Normal growth and maturation of bone, hair, teeth, c.t., and

nervous tissue require thyroid hormone.

6. Both T3 and T4 play a permissive role for GH and GH does not

have its normal effect on tissues if T3 and T4 are lacking.7. See Table 18.4 for effects of hypo- and hypersecretion

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Regulation of T3 and T4 Secretion

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Regulation of Calcitonin Secretion

Produced by parafollicular cells

Secretion triggered by high Ca2+

concentration in blood; acts to decreaseCa2+ concentration

Primary target tissue: bone. Decreases

osteoclast activity, lengthens life span

of osteoblasts.

P th id Gl d

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Parathyroid Glands Embedded in thyroid

Two glands on each side Secrete PTH: target tissues arebone, kidneys and intestines.

Increases blood calcium andphosphate levels

Stimulates osteoclasts

Promotes calcium reabsorption bykidneys and PO4 excretion

Increases synthesis of vitamin Dwhich, in turn, increases absorptionof Ca and PO4 by intestines. Netloss of PO4 under influence of

PTH. Regulation depends on calcium

levels.

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Figure 16.11

Effects of Parathyroid Hormone

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Adrenal Glands

Near superior poles ofkidneys; retroperitoneal

Inner medulla; outercortex

Medulla: formed fromneural crest; sympathetic.Secretes epinephrine andnorepinephrine

Cortex: three zones from

superficial to deep Zona glomerulosa

Zona fasciculata

Zona reticularis

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H f Ad l C

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Hormones of Adrenal Cortex

Mineralocorticoids: Zona glomerulosa

Aldosterone produced in greatest amounts. Increasesrate of sodium reabsorption by kidneys increasingsodium blood levels

Glucocorticoids: Zona fasciculata

Cortisol is major hormone. Increases fat and proteinbreakdown, increases glucose synthesis, decreasesinflammatory response

Androgens: Zona reticularis

Weak androgens secreted then converted to testosteroneby peripheral tissues. Stimulate pubic and axillary hairgrowth and sexual drive in females

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Regulation of Cortisol Secretion

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Figure 16.15

Stress and the Adrenal Gland

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Pancreas

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Pancreas

Located along small intestine and

stomach; retroperitoneal Exocrine gland

Produces pancreatic digestive

juices

Endocrine gland

Consists of pancreatic islets

Composed of

Alpha cells; secrete glucagon

Beta cells; secrete insulin

Delta cells; secrete somatostatin

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A 29-amino-acid polypeptide hormone that is a

potent hyperglycemic agent

Its major target is the liver, where it promotes: Glycogenolysis the breakdown of glycogen to

glucose

Gluconeogenesissynthesis of glucose from lactic acid

and noncarbohydrates Release of glucose to the blood from liver cells

Glucagon

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Target tissue is the liver, adipose tissue, muscle,and satiety center of hypothalamus

A 51-amino-acid protein consisting of two amino

acid chains linked by disulfide bonds

Synthesized as part of proinsulin and then excised

by enzymes, releasing functional insulin

Insulin:

Lowers blood glucose levels Enhances transport of glucose into body cells

Counters metabolic activity that would enhance blood

glucose levels

Insulin

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Figure 16.18

Diabetes Mellitus (DM)

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Regulation of Insulin Secretion

Regulation of Blood Nutrient Levels

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g

During Exercise

Hormones of the Reproductive System

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Hormones of the Reproductive System

Male: Testes

Testosterone

Regulates production of sperm

cells and development and

maintenance of male

reproductive organs and

secondary sex characteristics

Inhibin

Inhibits FSH secretion

Female: Ovaries

Estrogen and Progesterone

Uterine and mammary glanddevelopment and function,external genitalia structure,

secondary sex characteristics,menstrual cycle

Inhibin

Inhibits FSH secretion

Relaxin

Increases flexibility ofsymphysis pubis

Pineal Body

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Pineal Body

In epithalamus; produces melatonin and arginine

vasotocin

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Effects of Aging on

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Effects of Aging on

Endocrine System

Gradual decrease in secretory activity of some glands

GH as people age except in people who exercise regularly

Melatonin

Thyroid hormones Kidneys secrete less renin

Familial tendency to develop type II diabetes

151 endocrine

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