1. Chapter 18: The Endocrine System
Copyright 2009, John Wiley & Sons, Inc.

4. Nervous and Endocrine Systems
Act together to coordinate functions of all body systems
Nervous system
Nerve impulses/ Neurotransmitters
Faster responses, briefer effects, acts on specific target
Endocrine system
Hormone – mediator molecule released in a part of the body to regulates activity of cells in other parts
Slower responses, effects last longer, broader influence
Copyright 2009, John Wiley & Sons, Inc.

5. Nervous and Endocrine Systems
Copyright 2009, John Wiley & Sons, Inc.

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Body Glands
2 kinds of glands
Exocrine – ducted
Sweat, mucous, and digestive glands.
Endocrine – ductless
Secrete products into interstitial fluid, diffuse into blood
Endocrine glands include
Pituitary, thyroid, parathyroid, adrenal and pineal glands
Organs not exclusively endocrine glands
Hypothalamus, thymus, pancreas, ovaries, testes, kidneys, stomach, liver, small intestine, skin, heart, adipose tissue, and placenta.
Copyright 2009, John Wiley & Sons, Inc.

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Hormone Activity
Hormones work through receptors
Hormones affect only specific target tissues with specific receptors
Receptors constantly synthesized and broken-down
Copyright 2009, John Wiley & Sons, Inc.

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Hormone Activity
Hormones work through receptors
Hormones affect only specific target tissues with specific receptors
Receptors constantly synthesized and broken-down
Down-regulation & Up-regulation
Copyright 2009, John Wiley & Sons, Inc.

9. Copyright 2009, John Wiley & Sons, Inc.
Hormone Activity
Hormones work through receptors
Hormones affect only specific target tissues with specific receptors
Receptors constantly synthesized and broken-down
They operate within feedback systems to maintain an optimal internal environment
They are excreted by the kidney, deactivated by the liver or by other mechanisms
Copyright 2009, John Wiley & Sons, Inc.

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Hormone types
Circulating : circulate in blood throughout body
Local hormones : act locally
Paracrine – act on neighboring cells
Autocrine – act on the same cell that secreted them
Copyright 2009, John Wiley & Sons, Inc.

11. Chemical classes of hormones
Lipid-soluble – use transport proteins
Steroid
Thyroid
Nitric oxide (NO)
Water-soluble – circulate in “free” form
Amine
Peptide/ protein
Eicosanoid
Copyright 2009, John Wiley & Sons, Inc.

12. Lipid-soluble Hormones
Steroids
lipids derived from cholesterol on SER
different functional groups attached to core of structure provide uniqueness
Thyroid hormones
tyrosine ring plus attached iodines are lipid-soluble
Nitric oxide is gas

13. Water-soluble Hormones
Amine, peptide and protein hormones
modified amino acids or amino acids put together
serotonin, melatonin, histamine, epinephrine
some glycoproteins
Eicosanoids
derived from arachidonic acid (fatty acid)
prostaglandins or leukotrienes

14. Hormone Transport in Blood
Protein hormones circulate in free form in blood
Steroid (lipid) & thyroid hormones must attach to transport proteins synthesized by liver
improve transport by making them water-soluble
slow loss of hormone by filtration within kidney
create reserve of hormone
only .1 to 10% of hormone is not bound to transport protein = free fraction

16. Mechanisms of Hormone Action
Response depends on both hormone and target cell
Water-soluble hormones bind to receptors on the plasma membrane
Activates second messenger system
Amplification of original small signal
Lipid-soluble hormones bind to receptors inside target cells
Responsiveness of target cell depends on
Hormone’s concentration
Abundance of target cell receptors
Influence exerted by other hormones
Permissive, synergistic and antagonistic effects
Copyright 2009, John Wiley & Sons, Inc.

17. 1 2 4 3 5 1 2 6 4 3 5 1 2 4 3 1 2 3 1 2 1 Water-soluble hormone
Receptor
cAMP serves as a
second messenger
to activate protein
kinases
G protein
Protein kinases
cAMP
Activated
protein
Protein—
Second messenger
Activated adenylate
cyclase converts
ATP to cAMP
Activated protein
phosphorylate
cellular proteins
Millions of phosphorylated
proteins cause reactions that
produce physiological responses
Blood capillary
Binding of hormone (first messenger)
to its receptor activates G protein,
which activates adenylate cyclase
Adenylate cyclase
Target cell P
ADP
Protein
ATP 1 2 4 3 5
Water-soluble
hormone
Receptor
cAMP serves as a
second messenger
to activate protein
kinases
G protein
Protein kinases
cAMP
Activated
protein
Protein—
Second messenger
Phosphodiesterase
inactivates cAMP
Activated adenylate
cyclase converts
ATP to cAMP
Activated protein
phosphorylate
cellular proteins
Millions of phosphorylated
proteins cause reactions that
produce physiological responses
Blood capillary
Binding of hormone (first messenger)
to its receptor activates G protein,
which activates adenylate cyclase
Adenylate cyclase
Target cell P
ADP
Protein
ATP 1 2 6 4 3 5
Water-soluble
hormone
Receptor
cAMP serves as a
second messenger
to activate protein
kinases
G protein
Protein kinases
cAMP
Activated
protein
Second messenger
Activated adenylate
cyclase converts
ATP to cAMP
Activated protein
phosphorylate
cellular proteins
Blood capillary
Binding of hormone (first messenger)
to its receptor activates G protein,
which activates adenylate cyclase
Adenylate cyclase
Target cell
ATP 1 2 4 3
Protein— P
ADP
Protein
Water-soluble
hormone
Receptor
cAMP serves as a
second messenger
to activate protein
kinases
G protein
Protein kinases
cAMP
Second messenger
Activated adenylate
cyclase converts
ATP to cAMP
Blood capillary
Binding of hormone (first messenger)
to its receptor activates G protein,
which activates adenylate cyclase
Adenylate cyclase
Target cell
ATP 1 2 3
Activated
protein
Water-soluble
hormone
Receptor
G protein
cAMP
Second messenger
Activated adenylate
cyclase converts
ATP to cAMP
Blood capillary
Binding of hormone (first messenger)
to its receptor activates G protein,
which activates adenylate cyclase
Adenylate cyclase
Target cell
ATP 1 2
Water-soluble
hormone
Receptor
G protein
Blood capillary
Binding of hormone (first messenger)
to its receptor activates G protein,
which activates adenylate cyclase
Adenylate cyclase
Target cell 1

18. Amplification of Hormone Effects
Single molecule of hormone binds to receptor
Activates 100 G-proteins
Each activates an adenylate cyclase molecule which then produces 1000 cAMP
Each cAMP activates a protein kinase, which may act upon 1000’s of substrate molecules
One molecule of epinephrine may result in breakdown of millions of glycogen molecules into glucose molecules

19. Mechanisms of Hormone Action
Response depends on both hormone and target cell
Water-soluble hormones bind to receptors on the plasma membrane
Activates second messenger system
Amplification of original small signal
Lipid-soluble hormones bind to receptors inside target cells
Responsiveness of target cell depends on
Hormone’s concentration
Abundance of target cell receptors
Influence exerted by other hormones
Permissive, synergistic and antagonistic effects
Copyright 2009, John Wiley & Sons, Inc.

20. Lipid-soluble hormone diffuses into cell Blood capillary Activated1
Lipid-soluble
hormone
diffuses into cell
Blood capillary
Activated
receptor-hormone
complex alters
gene expression
Nucleus
Receptor
mRNA
Newly formed
mRNA directs
synthesis of
specific proteins
on ribosomes
DNA
Cytosol
Target cell
New proteins alter
cell's activity
Transport
protein
Free hormone
Ribosome
New 2 3 4 1
Lipid-soluble
hormone
diffuses into cell
Blood capillary
Activated
receptor-hormone
complex alters
gene expression
Nucleus
Receptor
mRNA
Newly formed
mRNA directs
synthesis of
specific proteins
on ribosomes
DNA
Cytosol
Target cell
Transport
protein
Free hormone
Ribosome 2 3 1
Lipid-soluble
hormone
diffuses into cell
Blood capillary
Activated
receptor-hormone
complex alters
gene expression
Nucleus
Receptor
mRNA
DNA
Cytosol
Target cell
Transport
protein
Free hormone 2 1
Lipid-soluble
hormone
diffuses into cell
Blood capillary
Target cell
Transport
protein
Free hormone

21. General Mechanisms of Hormone Action
Hormone binds to cell surface or receptor inside target cell
Cell may then
synthesize new molecules
change permeability of membrane
alter rates of reactions
Each target cell responds to hormone differently
liver cells---insulin stimulates glycogen synthesis
adipose---insulin stimulates triglyceride synthesis

22. Mechanisms of Hormone Action
Response depends on both hormone and target cell
Lipid-soluble hormones bind to receptors inside target cells
Water-soluble hormones bind to receptors on the plasma membrane
Activates second messenger system
Amplification of original small signal
Responsiveness of target cell depends on
Hormone’s concentration
Abundance of target cell receptors
Influence exerted by other hormones
Permissive, synergistic and antagonistic effects
Copyright 2009, John Wiley & Sons, Inc.

23. Hormonal Interactions
Permissive effect
a second hormone, is needed and strengthens the effects of the first
thyroid strengthens epinephrine’s effect upon lipolysis
Synergistic effect
Two hormones work together to produce a particular result. May be complimentary or as a greater effect
estrogen & LH are both needed for oocyte production
Antagonistic effects
two hormones with opposite effects
insulin promotes glycogen formation & glucagon stimulates glycogen breakdown
permissive effect. For example, epinephrine alone only
weakly stimulates lipolysis (the breakdown of triglycerides),
but when small amounts of thyroid hormones (T3 and T4) are
present, the same amount of epinephrine stimulates lipolysis
much more powerfully. Sometimes the permissive hormone increases
the number of receptors for the other hormone, and
sometimes it promotes the synthesis of an enzyme required for
the expression of the other hormone’s effects.
When the effect of two hormones acting together is greater
or more extensive than the effect of each hormone acting
alone, the two hormones are said to have a synergistic effect. For
example, normal development of oocytes in the ovaries requires
both follicle-stimulating hormone from the anterior pituitary and
estrogens from the ovaries. Neither hormone alone is sufficient.
When one hormone opposes the actions of another hormone,
the two hormones are said to have antagonistic effects. An example
of an antagonistic pair of hormones is insulin, which promotes
synthesis of glycogen by liver cells, and glucagon, which
stimulates breakdown of glycogen in the liver.

24. Control of Hormone Secretion
Regulated by
Signals from nervous system
Chemical changes in the blood
Other hormones
Chronotropic
Most hormonal regulation by negative feedback (Few examples of positive feedback)
Irregular control will lead to Disorders
Copyright 2009, John Wiley & Sons, Inc.

25. Types of endocrine disorders
Hypo-secretion
Primary hypo-secretion
Deficiency in resources for hormone production
Malfunction in hormone producing organ
Secondary hypo-secretion
Deficiency in tropic “regulatory” hormone
Hyper-secretion
Hypo-responsiveness
Abnormal or deficiency in receptors
Lack of activation enzyme
Hyper-responsiveness
Hormonal upregulation of receptor population
(Example) Thyroid hormone to epinephrine receptor