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ObjectivesObjectives

To define the endocrine system and associated To define the endocrine system and associated terminology.terminology.

To identify the different organs recognized as To identify the different organs recognized as being part of the End. System.being part of the End. System.

To identify the different ways that hormones may To identify the different ways that hormones may be classified.be classified.

To describe the action of hormones.To describe the action of hormones.

To list the different hormones produced by the To list the different hormones produced by the

pituitary gland and their respective actions.pituitary gland and their respective actions.

Role of the Endocrine SystemRole of the Endocrine System

Communication & RegulationCommunication & Regulation

Consists of the hormones and the various Consists of the hormones and the various

cells and glands that secrete them, as well cells and glands that secrete them, as well

as the target cells receiving the message.as the target cells receiving the message.

RegulatesRegulates

MetabolismMetabolism

GrowthGrowth

Water RegulationWater Regulation

Reproductive Cycles & SeasonsReproductive Cycles & Seasons

Response to StressResponse to Stress

MetamorphosisMetamorphosis

Stimulates blood cell productionStimulates blood cell production

LactationLactation

GlandGland

An An organorgan that synthesizes a specificthat synthesizes a specific

chemical substance.chemical substance.

Then secretes this substance either through aThen secretes this substance either through a

duct or onto the surface of the body or directlyduct or onto the surface of the body or directly

into the bloodstream.into the bloodstream.

Endocrine vs. ExocrineEndocrine vs. Exocrine

Anatomy of the Endocrine SystemAnatomy of the Endocrine System HormonesHormones

A chemical messenger liberated by a certain type of gland A chemical messenger liberated by a certain type of gland and transported in the blood to a specific (target) organ.and transported in the blood to a specific (target) organ.

“…..molecular triggers”“…..molecular triggers”

Types:Types:

Based on composition (a.a., protein, lipid)Based on composition (a.a., protein, lipid)

Based on speed (fast vs. slow acting).Based on speed (fast vs. slow acting).

Seconds Seconds �� days days

Free vs. BoundFree vs. Bound

Effect on target cellsEffect on target cells

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Target Cell SpecificityTarget Cell Specificity

Generalizations about receiving cells.Generalizations about receiving cells.> Must have a specific protein receptor to accept > Must have a specific protein receptor to accept

the Hormone.the Hormone.> Binding Hormone with the receptor “turns on” > Binding Hormone with the receptor “turns on”

some genesome gene--determined function.determined function.

Cell activation depends upon:Cell activation depends upon:1) Blood levels of the hormone.1) Blood levels of the hormone.

2) Relative numbers of receptor sites.2) Relative numbers of receptor sites.3) Affinity (strength) of the bond3) Affinity (strength) of the bond

Mechanisms of Hormone ActionMechanisms of Hormone Action

Hormone action on target cellsHormone action on target cells1.1. Alter plasma membrane permeability of Alter plasma membrane permeability of

membrane potential by opening or closing membrane potential by opening or closing ion channelsion channels

2.2. Stimulate synthesis of proteins or regulatory Stimulate synthesis of proteins or regulatory molecules molecules

3.3. Activate or deactivate enzyme systemsActivate or deactivate enzyme systems

4.4. Induce Induce secretorysecretory activityactivity

5.5. Stimulate action e.g. mitosis Stimulate action e.g. mitosis

Action of HormonesAction of Hormones

Slow acting Slow acting –– long lasting e.g. steroidlong lasting e.g. steroid

Fast acting Fast acting –– short duration e.g. peptide short duration e.g. peptide hormones like hormones like thyroxinethyroxine..

Figure 16.3, step 1

Receptor-hormonecomplex

Receptorprotein

Cytoplasm

Nucleus

Extracellular fluid

Steroidhormone

The steroid hormonediffuses through the plasmamembrane and binds anintracellular receptor.

Plasmamembrane

1111

Figure 16.3, step 2

Receptor-hormonecomplex

Receptorprotein

Cytoplasm

Nucleus

Extracellular fluid

Steroidhormone

The steroid hormonediffuses through the plasmamembrane and binds anintracellular receptor.

The receptor-hormone complex entersthe nucleus.

Plasmamembrane

1111

2222

Figure 16.3, step 3

DNA

Hormoneresponseelements

Receptor-hormonecomplex

Receptorprotein

Cytoplasm

Nucleus

Extracellular fluid

Steroidhormone

The steroid hormonediffuses through the plasmamembrane and binds anintracellular receptor.

The receptor-hormone complex entersthe nucleus.

The receptor- hormonecomplex binds a hormoneresponse element (aspecific DNA sequence).

Plasmamembrane

1111

2222

3333

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Figure 16.3, step 4

mRNA

DNA

Hormoneresponseelements

Receptor-hormonecomplex

Receptorprotein

Cytoplasm

Nucleus

Extracellular fluid

Steroidhormone

The steroid hormonediffuses through the plasmamembrane and binds anintracellular receptor.

The receptor-hormone complex entersthe nucleus.

The receptor- hormonecomplex binds a hormoneresponse element (aspecific DNA sequence).

Binding initiatestranscription of thegene to mRNA.

Plasmamembrane

1111

2222

3333

4444

Figure 16.3, step 5

mRNA

New protein

DNA

Hormoneresponseelements

Receptor-hormonecomplex

Receptorprotein

Cytoplasm

Nucleus

Extracellular fluid

Steroidhormone

The steroid hormonediffuses through the plasmamembrane and binds anintracellular receptor.

The receptor-hormone complex entersthe nucleus.

The receptor- hormonecomplex binds a hormoneresponse element (aspecific DNA sequence).

Binding initiatestranscription of thegene to mRNA.

The mRNA directsprotein synthesis.

Plasmamembrane

1111

2222

3333

4444

5555

Other tissues and organsOther tissues and organs

…That produce hormones include:

- Adipose cells

- Thymus- Cells in the walls of

the small intestine & stomach

- Kidneys

- Heart

PituitaryPituitary

Formerly known as “Master Gland”Formerly known as “Master Gland”

a.k.a. a.k.a. HypophysisHypophysis

2 parts2 parts

Anterior Pituitary = Anterior Pituitary = adenohypophysisadenohypophysisGlandular tissue Glandular tissue

Posterior Pituitary = Posterior Pituitary = neurohypophysisneurohypophysis

(H’s produced in hypothalamus)(H’s produced in hypothalamus)PituicytesPituicytes ((glialglial--like supporting cells) & nerve fiberslike supporting cells) & nerve fibers

Figure 16.4c

(c) Hormonal Stimulus

Hypothalamus

Thyroidgland

Adrenalcortex

Gonad(Testis)

Pituitarygland

1 The hypothalamus secreteshormones that…

2 …stimulatethe anteriorpituitary glandto secretehormonesthat…

3 …stimulate other endocrineglands to secrete hormones

PituitaryPituitary--Hypothalamic Hypothalamic

RelationshipsRelationshipsPosterior lobePosterior lobe

�� A down growth of hypothalamic neural tissueA down growth of hypothalamic neural tissue

�� Neural connection to the hypothalamusNeural connection to the hypothalamus

�� Nuclei of the hypothalamus synthesize the Nuclei of the hypothalamus synthesize the neurohormonesneurohormones oxytocinoxytocin and and antidiureticantidiuretichormone (ADH)hormone (ADH)

�� NeurohormonesNeurohormones are transported to the are transported to the posterior pituitaryposterior pituitary

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Hormones of the PituitaryHormones of the Pituitary

AnteriorAnterior

(all are peptide H’s)(all are peptide H’s)

-- Growth hormone GHGrowth hormone GH

-- Thyroid Stimulating TSHThyroid Stimulating TSH

-- Adrenocorticotropic ACTHAdrenocorticotropic ACTH

-- Follicle Stimulating FSHFollicle Stimulating FSH

-- Lutenizing LHLutenizing LH

-- ProlactinProlactin

-- Melanocyte stimulating MSHMelanocyte stimulating MSH

PosteriorPosterior

(neurohormones)(neurohormones)

-- Antidiuretic ADHAntidiuretic ADH

-- OxytocinOxytocin