Endocrine System
Glands that send messages via chemicals (hormones) hypothalamic-pituitary-target organ
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Function: communication inside the body to maintain homeostasis, control development and reproduction
Chemical messengers: neurotransmitters and hormones
Linked: many endocrine glands are regulated by a part of the nervous system
(hypothalamus)
Differences: path, speed and length of
response
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Hormones coordinate body functions
Hormone’s Path: production cell  blood  target cell
Production cell: part of the endocrine gland
Target cell: cell that has the receptors to this particular hormone
It will carry a response after hormone is recognized
Hormone-receptor recognition
is very important to regulate the body’s functions
Endocrine disruptors are synthetic chemicals that disrupt the endocrine system
How?
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2

How does an endocrine gland know when to release a hormone and when to stop releasing a hormone?
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Hypothalamus  pituitary  target organ
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The Hypothalamus is the master control center
It controls the endocrine glands
Via the anterior pituitary (AP)
By producing (red dots):
Releasing hormones:
Stimulate release of AP hormones
Inhibiting hormones:
Stop release of AP hormones
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Anterior and Posterior Pituitary
AP: produces hormones that stimulate other endocrine glands
PP: stores hormones made by the hypothalamus
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Estrogen, Testosterone, Progesterone
Function:
-Development of reproductive organs
-Secondary sexual characteristics (hair, mammary glands)
-Regulate reproductive cycle
How is the production of these sex hormones regulated?
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Pancreas secretes insulin and glucagon
Function: Manage blood glucose levels (BGL)
Insulin  lowers BGL
Glucagon  raises BGL
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Diabetes mellitus: two different causes for high blood glucose levels
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Knowledge of the action of these hormones comes from studying other vertebrates
The role of prolactin was discovered in fish, where it plays a role in osmoregulation
The importance of thyroid hormones in embryo development was studied in tadpoles
Studies of the hormone receptors of progesterone and estrogens from chicken oviducts
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Hormone regulation is present in all vertebrates
Hypothalamus  pituitary  organ
The basic plan is present in lampreys
But not hagfish
Hypothalamus hormones
Non mammalian vertebrates and
Fetal mammals produce a hormone
That is similar to oxytocin
Pituitary hormones are present in all vertebrates
The knowledge of the invertebrate endocrine systems is less well known
Hormonal regulation of molting and metamorphosis in insects
Ecdysone promotes molting (ecdysis) of the larva.
High levels of Juvenile Hormone
Results in _________
Low levels of JH
Results in __________
Possible applications of this knowledge?
Fenoxycarb mimics juvenile hormone
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