chapter 45

2004-2005 AP Biology

Chapter 45.

Endocrine SystemHormones

2004-2005AP 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

Axon Neurotransmitter

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

2004-2005AP 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

DNA mRNAProtein

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)

Growth

hor

mon

e (GH)

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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

Thyr

oxin

e se

cret

ion

rate

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

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Any Questions??