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CHAPTER 20

COORDINATION

20.3 HORMONES IN MAMMALS

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OBJECTIVES

List the types and characteristics of

hormones

Explain the mechanism of hormone

action

Gene activation: steroid hormone

Second messenger (cAMP): non steroid

hormone (adrenaline and glucagon)

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ENDOCRINE SYSTEM

is a collection of glands that produce chemicalmessenger called hormones.

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Endocrine glands characteristics :

Secretes hormones

Has no duct Secreted directly into the bloodstream

Has a rich supply of blood with a

relatively large number of bloodvessels

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HORMONES

is a chemicalmessenger secreted

by cells in theendocrine glands toregulate bodysgrowth, metabolism,sexual developmentand function

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HORMONE PROPERTIES.

Small soluble organic molecule

Travels in the blood

Effective in low concentrations Specific for a particular target cells

Produces response only when they reach

target cells

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T t ti P i i l ti

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Endocrine gland and hormone Target tissue Principal actions

HypothalamusReleasing and inhibiting

hormones

Anterior lobe of anterior Regulate secretion ofhormones by the anteriorpituitary

Hypothalamus (production)

Posterior lobe of pituitary(storage and release)Oxytocin

Antidiuretic hormone(ADH)

UterusMammary glands

Kidneys (collecting ducts)

Stimulates contractionStimulate ejection of milk into

ductsStimulates reabsorption ofwater; conserves water

Anterior lobe of pituitaryGrowth hormone

ProlactinThyroid stimulating hormone

(TSH)

General

Mamary glandsThyroid gland

Stimulates production ofinsulin-like growth factors;stimulates growth bypromoting protein synthesisStimulates milk productionStimulates secretion ofthyroid hormones; stimulates

increase in size of thyroidland

E d i l d d h T t ti P i i l ti

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Endocrine gland and hormone Target tissue Principal actions

Adrenocorticotropic hormone(ACTH)

Adrenal cortex Stimulates secretion ofadrenal corticol hormones

Gonadotropic hormones(follicle-stimulatinghormones[FSH]; luteinizinghormone[LH]

Gonads Stimulates gonad functionand growth

Thyroid glandThyroxine

General Stimulate metabolic rate;essential to normal growthand development

Islets of Langerhans of

PancreasInsulin

Glucagon

General

Liver; adipose tissue

Regulate sglucoseconcentration in blood;stimulates glycogenproduction;stimulates fatstorage and protein synthesisRegulates glucoseconcentration in blood;

stimulates glycogenbreakdown; mobilizes fat

E d i l d d h T t ti P i i l ti

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Endocrine gland and hormone Target tissue Principal actions

Adrenal cortexAldosterone

Cortisol

Kidney tubules

General

Maintain sodium andpotassium balance; increasesodium reabsorption;increase potassium excretionHelp body cope with longterm stress ; raise bloodglucose level; mobilize fat

OvaryEstrogens (estradiol)

Progestrone

General; uterus

Uterus; breast

Develop and maintain sexcharacteristics in female;stimulate growth of uterinelining

Stimulates development ofuterine lining

TestisTestosterone

Inhibin

General; reproductivestructures

Pituitary (anterior)

Develop and maintain sexcharacteristics in male;promotes spermatogenesisInhibits FSH release in male

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TYPES OF HORMONES

Can be divided into 2 groups:

1) Steroids

- large,

- Lipid soluble molecules

- Enable to permeate the cell membrane easily

- Synthesized from cholesterol

- Cortisol, aldosterone

- Testosterone

- Progesterone and estrogen

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2) Non-steroid

- Small

- Water soluble

- Unable to permeate the cell membrane.

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There are 2 groups of non steroid hormones:

a) Amine

The simplest hormonesEpinephrine, norepinephrineThyroxine (can enter cell)FSH,LH, prolactin

b) Peptide/proteinThe largest hormone groupOxytocin, ADH, insulin, GH, Glucagon

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Secreting cellTarget cell

receptor

Not a target cell (no receptor)

MECHANISM OF HORMONE

ACTION

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ormones are very specific

nly target cells that possess the particular protein receptor

that recognise the hormone will show the response

on target cells which lack the particular protein

eceptor do not respond to the hormones

MECHANISM OF HORMONE

ACTION

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The two most important effects are by:

GENE ACTIVATION

CYCLIC AMP ACTIVATION

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Involved the steroid hormones such as sexhormones

Secreted by an endocrine gland and transportedto the target cell via the blood circulation

Small, lipid soluble molecules Can pass freely through the plasma membrane

GENE ACTIVATION

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Hormones then bind with a receptor in the

cytoplasm

Certain receptor can be found in the nucleoplasm

Steroid hormone-receptor complex combines with

spesific site on the DNA

Activates or represses specific genes

Leading to mRNA transcription

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mRNA enters the cytoplasm

Translated into new proteins such as enzyme

Produce the changes in structure or metabolic

activity

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Involved peptide hormones such as adrenaline,

glucagon

Secreted by an endocrine gland and transported to

the target cell via the blood circulation

Insoluble in lipid

Cannot pass through the plasma membrane.

Hormone diffuses through the blood, into theinterstitial fluid, and then reaches the target cell .

Binds to the receptors present on the surface of the cell

CYCLIC AMP ACTIVATION

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This binding activates G protein which in turn activate

adenyl cyclase

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Adenylate cyclase converts ATP into cAMP cAMP then activates a variety of protein kinases in the

cell

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Each type of protein kinase phosphorylates a specific

protein

These phosphorylated proteins will alter the activity of thecells

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In this mechanism,

The hormone acts as the first messenger

Brings information to the plasma membraneonly

A second messenger, cAMP then relays the

message of the hormone inside the cell.

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Adrenaline/Glucagon

Receptor

G Protein

Adenyl cyclase

ATP cAMP

Activate protein kinase

Activate phosphorylase

Glycogen Glucose

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Cascade Effect

The action of one enzyme will activates another

enzymatic reaction resulting in many product of

molecules

At each stage in the process, amplification occurs

Each receptor can affect a number of G proteins

In turn can activate a number of molecules ofadenylate

cyclase

Then produce thousands of molecules of cAMP per second

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COMPARISON BETWEEN GENE

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COMPARISON BETWEEN GENE

ACTIVATION AND CYCLIC-AMP

MECHANISMS

Gene Activation cAMP Activation

Hormones are permeable to cellmembrane

Hormones are impermeable tocell membrane

Hormones bind to internalreceptor

Hormones bind to receptor onthe cell membrane

No second messenger Involves cAMP as the secondmessenger

The effects are caused by theprotein produced by the genes

The effects are caused by thesecond messenger

No cascade effect involved Cascade effect involved

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QUESTION:

Describe the different types of hormones

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Steroid hormones:

- lipid soluble

- permeable to cell membrane- pass into the cell, bind to an

internal receptor and turn on the

genes

- proteins produced by the genesare responsible for the effects

- E.g: male and female sex

hormones

Peptide hormones

- water soluble

- impermeable to cell membrane

- cannot pass through the cellmembrane, therefore, bind to thereceptors on the cell membrane.This causes the release of secondmessenger, cAMP inside the cell

- the second messengers areresponsible for the hormoneeffects

E.g: GH, ACTH, FSH

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ary Morgan has just been brought into the emergency

room of Ipoh Hospital. She is perspiring profusely and is

breathing rapidly and irregularly. Her breath smells likeacetone (sweet and fruity), and her blood glucose tests out

at 650mg/100ml of blood. She is in acidosis. What hormone

drug should be administered, and why?

Critical Thinking.

NEXT

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PLANT

HORMONES

AUXI N

GI BBERELLI N

CYTOKI NI NS

ETHYLENEABSI SI C

ACI D

NEXTLECTURE