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The endocrine system is involved inregulating:
- – homeostasis
- – growth and development
- – Reproduction
- – metabolism
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The Endocrine and NervousSystems Compared
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The endocrine system is comprised of allglands or organs secreting hormones
• Pancreas, adrenals, hypothalamus, kidneys,pituitary, thyroid, ovaries and testes
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Categories of Chemical Signals
• Autocrine signals:
• Paracrine signals:
• Endocrine signals:
• Pheromones:
act on same cell that secretes them
act on neighboring cells
hormones carried by blood orother body fluids
released into environment, act onanother individual
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1. Communication by hormones
The specificity of cellular response is dictated byexpression of the receptor on the target cell
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Hormones : definition
- • Organic compounds
- • Secreted from the cells that synthesize them
- • Act on target cells remote from cell oforigin
- • Small concentration, large effects
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4. Hypothalamo-Pituitary-Endocrine Gland Axes
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HORMONES:
Anterior Pituitary:
GH
TSH
ACTH-->Kidney produces Corticosteroids
FSH and LH-->Estrogen and Progesterone and Testostorone
PROLACTIN-->Milk Production
POSTERIOR PITUITARY:
ADH-->Kidney water retention
OXYTOCIN->Uterine contractions and milk letdown
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FEEDBACK AND HORMONES
Short- and long-loopfeedback relationshipsbetween hypothalamic,pituitary, and third-glandHormones regulatehormonesynthesis and secretion.
negative-feedback regulates the axis
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Gonads: Ovaries
- • Female gonads
- • Two compartments– Steroidogenic– Gametogenic
- • Cyclic in function
- • Hormones associated with gametematuration were co-opted over evolutionarytime to regulate sexual behaviors.
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• Male gonads
- Two compartments– Steroidogenic– Gametogenic
- • Static function
- • Hormones associated with gametematuration were co-opted overevolutionary time to regulate sexualbehaviors.
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GROWTH HORMONE:Influences growth and metabolism:
Stimulators and Inhibitors
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Stimulators of GH secretion include:
- •growth hormone releasing hormone(GHRH)
- •sleep
- •exercise
- •dietary proteins
- Inhibitors of GH secretion include:
- •somatostatin
- •circulating concentrations of GH andIGF-1 (negative feedback)
- •dietary carbohydrate
- •glucocorticoids
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Gigantism -
overproduction of GH before puberty
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Acromegaly -
overproduction of GH after puberty
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Posterior Pituitary Hormones
- • Oxytocin
- – Milk let-down (e.g., baby crying)
- – Uterine contractions (e.g., labor induction)
- – Amnesic?
- • Vasopressin (AKA antidiuretic hormone, ADH)
- – Water balance
- – Blood pressure
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Classes of Hormones:
3
(1) Monoamines (Amino Acids and derivatives)
(2) Polypeptides
(3) Steroids
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Hormones derived from Amino Acids:
Epinephrine and Melatonin
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Hormones that are polypeptides
- TRH (tripeptide)
- ACTH (39 amino acids)
- PTH (84 amino acids)
- GH (191 with disulfide bonds)
- FSH,
- TSH,
- LH
- -are Glycoprotein
- -Synthesized in the ER
- -Transported to the Golgi complex
- -Packaged
- -secreted
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Hormones derived from Cholesterol: Steroids
- Aldosterone
- Testostorone
- estradiol
- Progesterone
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Controlling steroid synthesis
- • Steroid hormones are synthesized and secreted only ondemand
- • The rate of synthesis = rate of secretion
- • Control is achieved by stimulation the “rate limiting enzyme”
- • Uptake and availability of cholesterol is mandatory!
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Hormone Transport in Blood
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Hormones: mechanisms of actions
- • Amine and peptide hormones: membranereceptors and second messenger
- systems
- • Steroid hormones and thyroxine: controllinggene expression
- (via nuclear receptors)
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Oxytocin -
the love hormone..
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