2006-2007 AP Biology

Endocrine SystemHormones

AP 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

AP Biology

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

AP Biology

Regulation by chemical messengers

Axon

Neurotransmitter

Endocrine gland

Receptor proteins

Hormone carried by blood

Target cell

Neurotransmitters released by neurons Hormones release by endocrine glands

Receptor proteins

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Insect metamorphosis

Is regulated by hormones

Figure 45.1

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Three Key Events in Hormone Function

Three Key Events Reception Signal transduction Response

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Classes of Vertebrate Hormones Three major classes of molecules

function as hormones in vertebrates Proteins and peptides Amines derived from amino acids Steroids

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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 Non polar amines

Modified nonpolar amino acids: thyroxine

AP Biology

How do hormones act on target cells Protein-based

hormones hydrophilic & not

lipid soluble can’t diffuse across

membrane trigger secondary

messenger pathway activate cellular

response enzyme action, uptake or

secretion of molecules…

SECRETORYCELL

Hormonemolecule

VIABLOOD

Signal receptor

TARGETCELL

Signaltransductionpathway

Cytoplasmicresponse

Nuclearresponse

NUCLEUS

DNA

OR

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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

AP Biology

How do hormones act on target cells Lipid-based

hormones hydrophobic &

lipid-soluble diffuse across

membrane & enter cells

bind to receptor proteins in cytoplasm & nucleus

bind to DNA as transcription factors

SECRETORYCELL

Hormonemolecule

VIABLOOD

TARGETCELL

Signalreceptor

Signaltransductionand response

DNA

mRNA

NUCLEUS

Synthesis ofspecific proteins

AP Biologynucleus

cytoplasm

plasma membraneDNA

mRNA protein

steroid hormone blood

proteincarrier2

3

5

4

S

S

S

1S

Action of lipid (steroid) hormones

receptor protein

AP Biology

Multiple Effects The same hormone may have different

effects on target cells that have Different receptors for the hormone Different signal transduction pathways Different proteins for carrying out the

response

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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

AP Biology

The hormone epinephrine Has multiple effects in mediating the

body’s response to short-term stress

Epinephrine: Multiple Effects

Different receptors different cell responses

Epinephrine

receptor

Epinephrine

receptor

Epinephrine

receptor

Vesselconstricts

Vesseldilates Glycogen

breaks downand glucose is releasedfrom cell

(a) Intestinal blood vessel

(b) Skeletal muscleblood vessel

(c) Liver cell

Different intracellular proteins different cell responses

Glycogendeposits

Figure 45.4a–c

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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

AP Biology

Paracrine Signaling by Local Regulators

Paracrine signaling Various types of chemical signals elicit

responses in nearby target cells Local regulators have various functions and

include Cytokines – important in immune response Growth factors – stimulate cell proliferation

and differentiation Nitric oxide – (NO) relaxes neighboring smooth

muscles causing vasodialation Prostaglandins – important in semen and in

immune response promote fever and inflammation

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Fig. 11-5ab

Local signaling

Target cell

Secretoryvesicle

Secretingcell

Local regulatordiffuses throughextracellular fluid

(a) Paracrine signaling (b) Synaptic signaling

Target cellis stimulated

Neurotransmitter diffuses across synapse

Electrical signalalong nerve celltriggers release ofneurotransmitter

AP Biology

The major human endocrine glandsHypothalamus

Pineal gland

Pituitary gland

Thyroid glandParathyroid glands

Adrenal glands

Pancreas

Ovary(female)

Testis(male)

Figure 45.6

AP Biology

Major human endocrine glands and some of their hormones

Table 45.1

AP Biology

Major human endocrine glands and some of their hormones

Table 45.1

AP Biology

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

AP Biology

Relation Between the Hypothalamus and Pituitary Gland The hypothalamus, a region of the lower

brain Contains different sets of neurosecretory

cells

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Relation Between the Hypothalamus and Pituitary Gland

Some of these cells produce direct-acting hormones That are stored in and released from the

posterior pituitary, or neurohypophysis

Figure 45.7

Hypothalamus

Neurosecretorycells of thehypothalamus

Axon

Anteriorpituitary

Posteriorpituitary

HORMONE ADH Oxytocin

TARGET Kidney tubules Mammary glands,uterine muscles

AP Biology

Other hypothalamic cells produce tropic hormones That are secreted into the blood and transported

to the anterior pituitary or adenohypophysis

Tropic Effects OnlyFSH, follicle-stimulating hormoneLH, luteinizing hormoneTSH, thyroid-stimulating hormoneACTH, adrenocorticotropic hormone

Nontropic Effects OnlyProlactinMSH, melanocyte-stimulating hormoneEndorphin

Nontropic and Tropic EffectsGrowth hormone

Neurosecretory cellsof the hypothalamus

Portal vessels

Endocrine cells of theanterior pituitary

Hypothalamicreleasinghormones(red dots)

HORMONE FSH and LH TSH ACTH Prolactin MSH Endorphin Growth hormone

TARGET Testes orovaries

Thyroid Adrenalcortex

Mammaryglands

Melanocytes Pain receptorsin the brain

Liver Bones

Pituitary hormones(blue dots)

Figure 45.8

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The anterior pituitary Is a true-endocrine gland

The tropic hormones of the hypothalamus Control release of hormones from the

anterior pituitary

AP Biology

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)

2005-2006AP Biology

Negative Feedback Model

high

low

hormone 1

lowersbody condition

hormone 2

gland

specific body condition

raisesbody condition

gland

2005-2006AP Biology

Body Temperature

high

low

nerve signals

sweat

nerve signals

brain

body temperature

shiver brain

dilates surfaceblood vessels

constricts surfaceblood vessels

FeedbackNervous System Control

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liver

pancreas

liver

Blood Sugar

blood sugar level

insulin

body cells takeup sugar

from blood

liver storessugar

reducesappetite

glucagon

pancreas

liver releases

sugartriggershunger

high

low

FeedbackEndocrine System Control

2005-2006AP Biology

Maintenance of glucose homeostasisBeta cells ofpancreas are stimulatedto release insulininto the blood.

Insulin

Liver takesup glucoseand stores itas glycogen.

Body cellstake up moreglucose.

Blood glucose leveldeclines to set point;stimulus for insulinrelease diminishes.

STIMULUS:Rising blood glucose

level (for instance, aftereating a carbohydrate-

rich meal)

Homeostasis:Blood glucose level

(about 90 mg/100 mL)

Blood glucose levelrises to set point;

stimulus for glucagonrelease diminishes.

STIMULUS:Dropping blood glucoselevel (for instance, after

skipping a meal)

Alpha cells of pancreasare stimulated to releaseglucagon into the blood.

Liver breaksdown glycogenand releasesglucose intoblood.

GlucagonFigure 45.12

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Diabetes Mellitus Diabetes mellitus, perhaps the best-

known endocrine disorder Is caused by a deficiency of insulin or a

decreased response to insulin in target tissues

Is marked by elevated blood glucose levels

2005-2006AP Biology

Types of Diabetes

Type I diabetes mellitus (insulin-dependent diabetes) Is an autoimmune disorder in which the

immune system destroys the beta cells of the pancreas

Type II diabetes mellitus (non-insulin-dependent diabetes) Is characterized either by a deficiency of

insulin or, more commonly, by reduced responsiveness of target cells due to some change in insulin receptors

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Adrenal Hormones: Response to Stress The adrenal glands

Are adjacent to the kidneys Are actually made up of two glands: the

adrenal medulla and the adrenal cortex

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Adrenal Hormones: Response to Stress The adrenal medulla secretes

epinephrine and norepinephrine Hormones which are members of a

class of compounds called catecholamines

2005-2006AP Biology

Adrenal Hormones: Response to Stress

These hormones Are secreted in response to stress-

activated impulses from the nervous system

Mediate various fight-or-flight responses

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Adrenal Hormones: Response to Stress Hormones from the adrenal cortex

Also function in the body’s response to stress

Fall into three classes of steroid hormones

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Adrenal Hormones: Response to Stress Glucocorticoids, such as cortisol

Influence glucose metabolism and the immune system

Mineralocorticoids, such as aldosterone Affect salt and water balance

Sex hormones Are produced in small amounts

2005-2006AP Biology

Stress and the adrenal gland

Spinal cord(cross section)

Nervesignals

Nervecell

Releasinghormone

Stress

Hypothalamus

Anterior pituitary

Blood vessel

ACTH

Adrenalgland

Kidney

Adrenal medullasecretes epinephrineand norepinephrine. Adrenal cortex

secretesmineralocorticoidsand glucocorticoids.

Effects of epinephrine and norepinephrine:

1. Glycogen broken down to glucose; increasedblood glucose

2. Increased blood pressure

3. Increased breathing rate

4. Increased metabolic rate

5. Change in blood flow patterns, leading to increased alertness and decreased digestive and kidney activity

Effects ofmineralocorticoids:

1. Retention of sodiumions and water bykidneys

2. Increased bloodvolume and bloodpressure

Effects ofglucocorticoids:

1. Proteins and fatsbroken down andconverted to glucose,leading to increasedblood glucose

2. Immune system maybe suppressed

(b) Long-term stress response(a) Short-term stress response

Nerve cell

Figure 45.13a,b

2005-2006AP Biology

nephron

low

Blood Osmolarity

blood osmolarityblood pressure

ADH

increasedwater

reabsorption

increasethirst

renin

increasedwater & saltreabsorption

high

FeedbackEndocrine System Control

pituitary

angiotensinogenangiotensin

nephronadrenalgland

aldosterone

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Homology in hormones

prolactin

mammals

milkproduction

birds

fatmetabolism

amphibians

metamorphosis& maturation

fish

salt &water

balance

growth& development

What does this tell you about these hormones?

growthhormone

same gene family

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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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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

2005-2006AP Biology

corpusluteumovary

Female reproductive cycle

pregnancy

maintainsuterus lining

no

yes

Feedback

estrogenegg

matures &is released(ovulation)

builds up uterus lining

FSH & LH

progesterone

progesterone

fertilized egg(zygote)

HCG

corpus luteum breaks downprogesterone drops

menstruation

corpusluteum

maintainsuterus lining

GnRH

pituitarygland

hypothalamus