Download The Endocrine System

The Endocrine System
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Endocrine system –
the body’s second
great controlling
system
Nervous and Endocrine
Regulation
Delivery
Control
Response
Duration
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Review of glands
 Exocrine
 Endocrine
– pituitary, thyroid, parathyroid,
adrenal, pineal, thymus, ovaries,
testes, pancreas, hypothalamus
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Hormones
 Hormones
 Regulate the metabolic function of other cells
 Are classified as:
 Amino acid-based hormones
 Steroids
 Eicosanoids
 Target Cell
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How hormones activate cells:
 Amino acid based (amine) –
 Amines, thyroxine, peptide,
and protein hormones
 Second messenger
mechanism
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
Amino acid (Amine) based
1) Hormone binds
2) The G protein is then
activated
3) Activated G protein activates
the effector enzyme
adenylate cyclase
4) Adenylate cyclase generates
cAMP from ATP
5) cAMP activates protein
kinases (chemical reactions)
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How hormones work
Steroid based
gonadal and adrenocortical
hormones,
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Hormone Mode of Action

Changes in target cells
 Alter plasma membrane permeability
 Stimulate protein synthesis
 Activate or deactivate enzyme systems
 Induce secretory activity
 Stimulate mitosis
Hormone inactivation and removal
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Target cell receptor specificity



Hormones affect target cells only.
Bind to cell surface or intracellular protein receptors.
Further activation is dependent on 3 other factors:
1) Blood levels
2)
Relative number of receptors
3)
Affinity of those receptors
a) Up-regulation
b) Down-regulation
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Interactions of Hormones at Target Cells
 Three types of hormone interaction
 Permissiveness
 Synergism
 Antagonism
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Stimuli –
Control of hormone release
1)
Humoral
2)
Neural
3)
Hormonal
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Questions:
17.2 Which system produces a quicker response, the nervous system or the
endocrine system? Which system produces a longer-acting response?
17.4 Why would follicle stimulating hormone act on the ovaries but not on the
thyroid?
17.6 Where do lipid-soluble hormones bind to their target cells?
water soluble hormones bind to their target cells?
Where do
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?
17.9 What are the three influences over hormone secretion?
Why are organs such as the kidneys, stomach, heart, and skin considered to
be part of the endocrine system?
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