Hormones & Endocrine Systems

Chapter 40: pp. 735 - 754

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(Caterpillar): © Doug Wechsler/Animals Animals/Earth Scenes; (Moth): © Richard Kolar/Animals Animals/Earth Scenes

OutlineEndocrine Glands

PheromonesSteroid HormonesPeptide Hormones

Hypothalamus and Pituitary GlandOther Endocrine Glands and Hormones

ThyroidParathyroid AdrenalPancreasGonads

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Endocrine Gland

• The endocrine system functions differently from the nervous system.

• An endocrine system consists of glands that coordinate body activities through hormones

• Chemical signals are used between individuals, between body parts, and between cells

• Both the nervous system and the endocrine system rely on negative feedback mechanisms.

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The Human Endocrine System

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ovary (female)

HYPOTHALAMUS

Releasing and inhibiting hormones: regulate the anterior pituitary

PITUITARY GLAND

Posterior Pituitary

Antidiuretic (ADH): water reabsorption by kidneys

Oxytocin: stimulates uterine contraction and milk letdown

Anterior PituitaryThyroid stimulating (TSH): stimulates thyroid

Adrenocorticotropic (ACTH): stimulates adrenal cortex

Gonadotropic (FSH, LH): egg and sperm production; sex hormone production

Prolactin (PL): milk production

Growth (GH): bone growth, protein synthesis, and cell division

THYROID

Thyroxine (T4) and triiodothyronine (T3): increase metabolic rate; regulates growth and development

Calcitonin: lowers blood calcium level

ADRENAL GLAND

Adrenal cortex

Glucocorticoids (cortisol): raises blood glucose level; stimulates breakdown of protein

Mineralocorticoids (aldosterone): reabsorption of sodium and excretion of potassiumSex hormones: reproductive organs and bring about sex characteristics

Adrenal medullaEpinephrine and norepinephrine: active in emergency situations; raise blood glucose level

parathyroid glands(posterior surfaceof thyroid)

PINEAL GLAND

Melatonin: controls circadian and circannual

PARA THYROIDS

Parathyroid hormone (PTH): raises blood

THYMUS

Thymosins: production and maturation of T lymphocytes

PANCREAS

Insulin: lowers blood glucose level and promotes glycogen buildup

Glucagon: raises blood glucose level and promotes glycogen breakdown

GONADS

TestesAndrogens (testosterone):male sex characteristics

OvariesEstrogens and progesterone:female sex characteristics

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testis(male)

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Modes of Action of the Nervous and Endocrine Systems

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receptor

receptor

neurotransmitter

pancreas

arteriole

liverinsulin

liver cell

axon terminal

vesicle

b. Reception of insulin, a hormone

a. Reception of a neurotransmitter

axon ofnerve fiber

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Chemical Signals

• Pheromones– Chemical signals that work at a distance between

individuals

– A woman’s axillary extract can alter another woman’s menstrual cycle

• Hormones– Chemical signals that work

• At a distance between organs, or

• Locally between adjacent cells

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Target Cell Concept

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hormone

capillary

nontarget cell

receptors

target cells

Action of Hormones

HormonesChemical signals produced by one cell that regulate

the metabolism of other cellsSteroid Hormones

Can cross cell membranes

Peptide HormonesMost bind to receptor in plasma membrane

First Messenger

Causes internal release of cAMP Second Messenger

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Peptide Hormone

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capillary

receptor protein

glycogen

1. Hormone binds to a receptor in the plasma membrane.

activatedenzyme

2. Binding leads to activation of an enzyme that changes ATP to cAMP.

cAMP(second messenger)

3. cAMP activates an enzyme cascade.

4. Many molecules of glycogen are broken down to glucose, which enters the bloodstream.

glucose(leaves celland goesto blood)

ATP

peptide hormone(first messenger)

plasmamembrane

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Steroid Hormone

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ribosome

protein

nucleus

cytoplasm

1. Hormone diffuses through plasma membrane because it is lipid soluble.

steroidhormone

plasmamembrane

nuclearpore

2. Hormone binds to receptor inside nucleus.

DNAreceptorprotein

mRNA

3. Hormone-receptor complex activates gene and synthesis of a specific mRN molecule.

4. mRNA moves to ribosomes, and protein synthesis occurs.

mRNA

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Human Endocrine System

• Endocrine glands– Ductless glands that secrete hormones directly into

the bloodstream• Most endocrine hormones are peptides

• Only gonads and adrenal cortex produce steroid hormones

– Effects of hormones are moderated in two ways• Negative feedback opposes release

• Antagonistic hormones oppose each other’s actions

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Hypothalamus and Pituitary GlandHypothalamus regulates internal environmentActs through autonomic systemAlso controls glandular secretions of pituitary gland

Posterior PituitaryAntidiuretic Hormone (ADH)

Controlled by negative feedbackOxytocin

Controlled by positive feedback

Anterior PituitaryHypothalamus controls by producing

Hypothalamic-releasing hormones, andHypothalamic-inhibiting hormones

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Hypothalamus and the Pituitary

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hypothalamus

Posterior pituitary Anterior pituitary

portal system

1. Neurosecretory cells produce ADH and oxytocin.

2. These hormones move down axons to axon endings.

3. When appropriate, ADH and oxytocin are secreted from axon endings into the bloodstream.

1. Neurosecretory cells produce hypothalamic-releasing and hypothalamic-inhibiting hormones.

2. These hormones are secreted into a portal system.

3. Each type of hypothalamic hormone either stimulates or inhibits production and secretion of an anterior pituitary hormone.

4. The anterior pituitary secretes its hormones into the bloodstream, whereby they are then delivered to specific cells, tissues, and glands.

Thyroid:thyroid-stimulatinghormone (TSH)

Adrenal cortex:adrenocorticotropichormone (ACTH)

Kidney tubules:antidiuretichormone (ADH)

Smooth musclein uterus:oxytocin

Mammary glands:oxytocin

Mammary glands:prolactin (PRL)

Bones, tissues:growth hormone(GH)

Ovaries, testes:gonadotropichormones (FSH, LH)

opticchiasm

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Anterior Pituitary Hormones

Anterior pituitary hormones that affect other glands:Thyroid-Stimulating Hormone (TSH)Adrenocorticotropic Hormone (ACTH)Gonadotropic Hormones

Anterior pituitary hormones that do NOT affect other glandsProlactin (PRL)Melanocyte-Stimulating Hormone (MSH)Growth Hormone (GH)

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Effect of Growth Hormone

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a. b.

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Acromegaly

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From Clinical Pathological Conference, "Acromegaly, Diabetes, Hypermetabolism, Proteinura and Heart Failure", American Journal of Medicine, 20 (1956) 133. Reprinted with permission from Excerpta Medica Inc.

Age 9 Age 16 Age 33 Age 52

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Thyroid Glands

• Composed of large number of follicles filled with– Triiodothyronine (T3), and

– Thyroxine (T4)

• Thyroid hormones increase metabolic rate

• Thyroid-induced abnormalities– Simple goiter - Poor hormone production

– Cretinism - Poor thyroid development

– Myxedema - Hypothyroidism

– Exophthalmic goiter - Hyperthyroidism

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Abnormalities of the thyroid

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a: © Bruce Coleman, Inc./Alamy; b: © Medical-on-Line/Alamy; c: © Dr. P. Marazzi/Photo Researchers, Inc. a. Simple goiter b. Congenital hypothyroidism c. Exophthalmic goiter

affected eye

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Calcitonin• Regulates blood calcium level (in part)• Secreted by thyroid gland when blood calcium level

rises• Brings about deposit of calcium in the bones• Low calcium level in blood stimulates the release of

parathyroid hormone (PTH)– Parathyroid hormone causes

• Phosphate level in blood to decrease, and• Calcium level in blood to increase

– Insufficient production of parathyroid hormone leads to tetany

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Regulation of Blood Calcium Level

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calcitonin

Homeostasis (normal blood Ca2+)

high blood Ca 2+

Thyroid glandsecretes

calcitonininto blood. Bones

take up Ca2+

from blood.

low blood Ca 2+

Blood Ca2+

lowers.

Blood Ca2+

rises.Parathyroid

glandsrelease PTHinto blood.

activatedvitamin D

parathyroidhormone

(PTH)

Intestinesabsorb Ca2+

from digestivetract.

Kidneysreabsorb Ca2+

from kidneytubules.

Bonesrelease Ca2+

into blood.

Adrenal Glands• Paired – One sits atop each kidney (ad-renal)• Each consists of outer cortex and inner

medulla– Inner portion, the adrenal medulla

• Produces– Epinephrine, and– Norepinephrine

• Short-term response to stress (fight or flight)– Outer portion, adrenal cortex

• Produces– Mineralocorticoids, and– Glucocorticoids

• Long-term response to stress

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Adrenal Glands

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epinephrine

norepinephrine

sympathetic fibers

adrenal medulla

Blood glucose level rises.

adrenal cortex

ACTH

Glucocorticoids

Mineralocorticoids

stress

glucocorticoids

mineralocorticoids

hypothalamus

spinal cord(cross section)

neurosecretorycells producehypothalamic-releasinghormone

Stress Response:Long Term

path of nerveimpulses

Protein and fat metabolisminstead of glucosebreakdown.

Reduction of inflammation;immune cells aresuppressed.

Sodium ions and waterare reabsorbed by kidney.

Blood volume andpressure increase.

Stress Response:Short Term

Heartbeat and bloodpressure increase.

Muscles becomeenergized.

anteriorpituitarysecretesACTH

neuroncell body

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Glucocorticoids

• Cortisol– Raises blood glucose level– Promotes breakdown of muscle proteins to amino

acids– Promotes metabolism of fatty acids– Counteracts inflammatory response

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Mineralocorticoids

AldosteronePromotes two renal functions:

Absorption of sodium, andExcretion of potassium

Renin-angiotensin-aldosterone systemRaises blood pressureAngiotensin II constricts arteriolesAldosterone causes kidneys to reabsorb sodium (causing water

retention)

Atrial natriuretic hormone (ANH) is antagonistic to aldosterone

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Regulation of Blood Pressure and Volume

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renin

aldosterone

Homeostasis (normal blood pressure)

low blood Na +

atrial natriuretichormone (ANH)

Kidneys excreteNa+ and water

in urine.

Heart secretesatrial natriuretichormone (ANH)

into blood.

Blood pressurelowers.

Blood pressurerises.

Kidneys secreterenin into blood.

Kidneysreabsorb Na+

and water fromkidney tubules.

Adrenal cortexsecretes

aldosteroneinto blood.

angiotensinI and II

high blood Na+

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Addison Disease

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a. b.

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a: © Custom Medical Stock Photos; b: © NMSB/Custom Medical Stock Photos

Cushing Syndrome

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(Both): Atlas of Pediatric Physical Diagnosis, Second Edition by Zitelli & Davis, 1992. Mosby-Wolfe Europe Limited, London, UK

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Pancreas• Made up of exocrine and endocrine tissue

– Endocrine Portion of the Pancreas:• Consists of pancreatic islets• Produce and secrete

– Insulin» Secreted during high blood glucose level» Stimulates uptake of glucose by cells

– Glucagon» Secreted during low blood glucose level» Stimulates liver to break down glycogen

– Exocrine Portion of the Pancreas:• Secretes enzymes and buffers into intestine

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Regulation of Blood Glucose Level

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high blood glucose

low blood glucose

insulin

glucagon

Liver storesglucose from

blood asglycogen.

Pancreatic isletof Langerhans

After eating,pancreas

secretes insulininto blood.

Muscle cellsstore glycogen

and build protein.

Adipose tissueuses glucosefrom bloodto form fat.

Homeostasis (normal blood glucose)

Blood glucoselevel lowers.

Before eating,pancreas secretes

glucagon intoblood.

Liver breaksdown glycogen

to glucose.Glucose enters

blood.

Adipose tissuebreaks down fat.

Pancreatic isletof Langerhans

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Other Endocrine Glands

• Gonads– Testes

• Produce testosterone

• Secondary sex characteristics

– Ovaries• Produce estrogen and progesterone

• Reproduction

• Secondary sex characteristics

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The Effects of Anabolic Steroid Use

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deepening of voice in women severe acne

balding in men and women; hair on face and chest in women

breast enlargement in menand breast reduction in women

liver dysfunctionand cancer

kidney disease andretention of fluids,called "steroid bloat"

reduced testicularsize, low sperm count,and impotency

'roid mania–delusions and hallucinations;depression upon withdrawal

high blood cholesterol andatherosclerosis; high bloodpressure and damage to heart

in women, increasedsize of ovaries;cessation of ovulationand menstruation

stunted growth inyoungsters by pre-maturely halting fusionof the growth plates

Other Endocrine Glands

Pineal GlandProduces melatoninInvolved in Circadian rhythms

Thymus GlandSecrete thymosinsAid in differentiation of lymphocytes

ProstaglandinsProduced within cells Not distributed in blood

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Melatonin Production

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6 P.M. 6 A.M.

b. winter

a. experimental

c. summer

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© The McGraw-Hill Companies, Inc./ Evelyn Jo Johnson, photographer

ReviewEndocrine Glands

PheromonesSteroid HormonesPeptide Hormones

Hypothalamus and Pituitary GlandOther Endocrine Glands and Hormones

ThyroidParathyroid AdrenalPancreasGonads

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