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The Endocrine SystemThe Endocrine System

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Endocrine systemEndocrine system – – the body’s second the body’s second great controlling great controlling systemsystem

Nervous and Endocrine

Regulation

Delivery

Control

Response

Duration

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Review of glandsReview of glands

ExocrineExocrine

EndocrineEndocrine– – pituitary, thyroid, parathyroid, pituitary, thyroid, parathyroid,

adrenal, pineal, thymus, ovaries, adrenal, pineal, thymus, ovaries, testes, pancreas, hypothalamus testes, pancreas, hypothalamus

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HormonesHormones

HormonesHormones Regulate the metabolic function of other cellsRegulate the metabolic function of other cells Are classified as: Are classified as:

Amino acid-based hormonesAmino acid-based hormones SteroidsSteroids EicosanoidsEicosanoids

Target CellTarget Cell

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How hormones activate cells:How hormones activate cells:

Amino acid basedAmino acid based (amine) – (amine) –

Amines, thyroxine, peptide, Amines, thyroxine, peptide, and protein hormonesand protein hormones

Second messenger Second messenger mechanismmechanism

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Amino acid (Amine) basedAmino acid (Amine) based

1)1) Hormone bindsHormone binds

2)2) The G protein is then The G protein is then activated activated

3)3) Activated G protein activates Activated G protein activates the effector enzyme the effector enzyme adenylate cyclaseadenylate cyclase

4)4) Adenylate cyclase generates Adenylate cyclase generates cAMP from ATPcAMP from ATP

5)5) cAMP activates protein cAMP activates protein kinases (chemical reactions)kinases (chemical reactions)

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Steroid based

gonadal and adrenocortical hormones,

How hormones workHow hormones work

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Hormone Mode of ActionHormone Mode of Action Changes in target cellsChanges in target cells

Alter plasma membrane permeability Alter plasma membrane permeability Stimulate protein synthesis Stimulate protein synthesis Activate or deactivate enzyme systemsActivate or deactivate enzyme systems Induce secretory activityInduce secretory activity Stimulate mitosisStimulate mitosis

Hormone inactivation and removalHormone inactivation and removal

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Target cell receptor specificityTarget cell receptor specificity

Hormones affect target cells only. Hormones affect target cells only. Bind to cell surface or intracellular protein receptors.Bind to cell surface or intracellular protein receptors.

Further activation is dependent on 3 other factors:Further activation is dependent on 3 other factors:

1)1) Blood levelsBlood levels

2)2) Relative number of receptors Relative number of receptors

3)3) Affinity of those receptorsAffinity of those receptors a)a) Up-regulationUp-regulation

b)b) Down-regulationDown-regulation

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Three types of hormone interactionThree types of hormone interaction

PermissivenessPermissiveness

Synergism Synergism

AntagonismAntagonism

Interactions of Hormones at Target CellsInteractions of Hormones at Target Cells

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Stimuli –Stimuli –Control of hormone releaseControl of hormone release

1)1) HumoralHumoral

2)2) NeuralNeural

3)3) HormonalHormonal

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Questions:Questions:

17.2 Which system produces a quicker response, the nervous system or the 17.2 Which system produces a quicker response, the nervous system or the endocrine system? Which system produces a longer-acting response?endocrine system? Which system produces a longer-acting response?

17.4 Why would follicle stimulating hormone act on the ovaries but not on the 17.4 Why would follicle stimulating hormone act on the ovaries but not on the thyroid?thyroid?

17.6 Where do lipid-soluble hormones bind to their target cells? Where do 17.6 Where do lipid-soluble hormones bind to their target cells? Where do water soluble hormones bind to their target cells?water soluble hormones bind to their target cells?

17.7 Why is cyclic AMP considered to be a second messenger?17.7 Why is cyclic AMP considered to be a second messenger?

17.8 What factors determine the responsiveness of a target cell to a hormone?17.8 What factors determine the responsiveness of a target cell to a hormone?

17.9 What are the three influences over hormone secretion?17.9 What are the three influences over hormone secretion?

Why are organs such as the kidneys, stomach, heart, and skin considered to Why are organs such as the kidneys, stomach, heart, and skin considered to be part of the endocrine system?be part of the endocrine system?