2008-2009 AP Biology

Chapter 45.

Endocrine SystemHormones

2008-2009AP Biology

Regulation Why are hormones needed?

chemical messages from one body part to another

communication needed to coordinate whole body

homeostasis & regulation metabolism growth development maturation reproduction

growth hormones

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Regulation & Communication Animals rely on 2 systems for regulation

endocrine system ductless gland which secrete

chemical signals directly into blood chemical travels to target tissue slow, long-lasting response

nervous system system of neurons, central

nerve system transmits “electrical” signal to

target tissue fast, short-lasting response

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Regulation by chemical messengers

AxonNeurotransmitter

Endocrine gland

Receptor proteins

Hormonecarried by blood

Target cell

Neurotransmitters released by neurons Hormones release by endocrine glands

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Classes of Hormones Protein-based hormones

polypeptides small proteins: insulin, ADH

glycoproteins large proteins + carbohydrate: FSH, LH

amines modified amino acids: epinephrine, melatonin

Lipid-based hormones steroids

modified cholesterol: sex hormones, aldosterone

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How do hormones act on target cells Lipid-based hormones

lipid-soluble diffuse across membrane & enter cells

bind to receptor proteins in cytoplasm & then this hormone-receptor complex moves into nucleus

bind to receptor proteins in nucleus bind to DNA as transcription factors

2008-2009AP BiologyNucleus

Cytoplasm

Steroid hormone (S) passes through plasma membrane.

Inside target cell, the steroid hormone binds to a specific receptor protein in the cytoplasm or nucleus.

Hormone-receptor complex enters nucleus & binds to DNA, causing gene transcription

Protein is produced.

Protein synthesis is induced.

Plasma membrane

DNAmRNA

Protein

Steroidhormone

Blood plasma

Proteincarrier

1

2

2

3

3

5

5 4

4

S

S

S

1S

Action of steroid (lipid) hormones

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How do hormones act on target cellsSignal molecule

Cell surface receptorenzyme

G proteincAMP

Targetprotein

Nucleus

Cytoplasm

ATP

Protein-based hormones hydrophilic & not lipid

soluble can’t diffuse across

membrane trigger secondary (2°)

messenger pathway transmit “signal” across

membrane “signal transduction”

usually activates a series of 2° messengers multi-step “cascade”

activate cellular response enzyme action, uptake or

secretion of molecules, etc.

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Action of protein hormones

3

4

GTPactivatesenzyme

activatesenzyme

activatesenzyme

Receptorprotein

cAMP

Proteinhormone

ATP

1

2

Cytoplasm

Produces an action

proteinmessengercascade

G protein

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adrenal gland

Action of epinephrine (adrenalin)

3

4

GTPactivates

protein kinase-A

activatesphosphorylase

activates adenylyl cyclase

Receptorprotein cAMP

Epinephrine

ATP

1

2

Cytoplasm

G protein

Liver cell

GlucoseGlycogen

releasedto blood

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Benefits of a 2° messenger system

Amplification!

Signal molecule Receptor protein Activated adenylyl cyclase

Amplification

Amplification

Amplification

Amplification

GTP G protein

2

1

3

4

5

6

7

Enzymatic product

Enzyme

Protein kinase

cAMP

Not yetactivated

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Ductless glands release hormones into blood

Endocrine system

Duct glands = exocrine(tears, salivary)

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Major vertebrate hormones (1)

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Major vertebrate hormones (2)

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Endocrine & Nervous system links Hypothalamus = “master control center”

nervous system receives information from nerves around body

about internal conditions regulates release of hormones from pituitary

Pituitary gland = “master gland” endocrine system secretes broad range

of hormones regulating other glands

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Thyroid gland

Hypothalamus

Anteriorpituitary

Gonadotropic hormones:Follicle-stimulatinghormone (FSH) & luteinizing hormone (LH)

Mammaryglandsin mammals

Musclesof uterus

Kidneytubules

Posteriorpituitary

Thyroid-stimulating Hormone(TSH)

Antidiuretic hormone(ADH)

Adrenalcortex

Boneand muscle Testis

Ovary

Melanocytein amphibian

Adrenocorticotropic

hormone (ACTH) Melanocyte-stimulating hormone(MSH)

OxytocinProlactin (PRL)

Gro

wth

hor

mon

e (G

H)

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Homology in hormones

prolactin

mammals birds amphibiansfish

milkproduction

fatmetabolism

metamorphosis& maturation

salt &water

balance

growthhormone

growth& development

What does this tell you about these hormones?

same gene family

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Hormones & Homeostasis Negative feedback

stimulus triggers control mechanism that inhibits further change body temperature sugar metabolism

Positive feedback stimulus triggers

control mechanism that amplifies effect lactation labor contractions

Anterior pituitary

Inhibition

–

Inhibition

Target glands

Hypothalamus

Releasing hormones(TRH, CRH, GnRH)

Tropic hormones(TSH, ACTH, FSH, LH)

–

(thyroid, adrenal cortex, gonads)

Hormones

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- triggers release of glucose by liver

- stimulates appetite

Regulating blood sugar levels

- triggers uptake of glucose by body cells

- triggers storage in liver

- depresses appetite

pancreas

pancreas

beta islet cells

alpha islet cells

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Regulating blood osmolarityIf amount of dissolved material in blood too high, need to dilute blood

ADH

Dehydration Lowers blood volume & pressure

Increased waterretention

Increasedvasoconstrictionleading to higherblood pressureReduced

urine volume

Osmotic concentrationof blood increases

ADH synthesized in hypothalamus

ADH released from posterior pituitary into blood

Osmoreceptors NegativefeedbackNegative

feedback

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Regulating metabolism Hypothalamus

TRH = TSH-releasing hormone

Anterior Pituitary TSH = thyroid stimulating hormone

Thyroid produces thyroxine hormones metabolism & development

bone growth mental development metabolic use of energy blood pressure & heart rate muscle tone digestion reproduction

tyrosineiodine

thyroxine

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GoiterIodine deficiency causes thyroid to enlarge as it tries to produce thyroxine

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Homology in hormones

Days from emergence of forelimb

TRH rises

TRH TSH Thyroxine

–35 –30 –25 –20 –15 –10 –5 0 +5 +10

Th

yro

xin

e s

ecre

tio

n r

ate

Thyroxine stimulates metamorphosis in amphibians

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Regulating blood calcium levels

Increased blood Ca++

Thyroid

ParathyroidsLow blood Ca++

Parathyroidhormone (PTH)

Increased absorptionof Ca++ from intestine due to PTH activation of Vitamin D

Reabsorption of Ca++ &excretion of PO4

Osteoclasts dissolve CaPO4crystals in bone, releasing Ca++

–Negativefeedback

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Hormonal regulation of insect development

Neurosecretory cells

Larval molt Pupal molt Adult molt

ProthoracicglandLow amounts

Brain hormone

Juvenile hormone

Molting hormone

2008-2009 AP Biology

Any Questions??