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ENDOCRINE SYSTEM
--> made up of several glands or a group of cells that secrete chemical messages in our
bloodstreams; second messenger system of the body; Uses chemical messages called
“Hormones”
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Major processes controlled by hormones:
◼ Reproduction
◼ Growth and development
◼ Mobilization of body defenses
◼ Maintenance of much of homeostasis
 Homeostasis - hormones are used to balance chemicals in the body
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 Target cell - contains “receptors” where the hormone binds to
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✱ Hormonal stimuli → endocrine glands are activated by other hormones; when a gland
releases a hormone that causes another gland to also release hormones
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✱ Neural stimuli → Nerve impulse stimulate hormone release; most are under control of the
sympathetic nervous system
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Pineal Gland - behind hypothalamus
2)
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Pituitary gland - base of the brain
4)
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Parathyroid - in the neck
6
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) Adrenal - on top of the kidney
8
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) Testes - Lower abdomen(Male)
Ovaries - Lower abdomen(Female)

Image from https://www
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gov
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Pituitary Gland
 Size of a grape; hangs by a stalk from the hypothalamus; directed by Hypothalamus
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 Growth hormone(GH) - affects the growth of skeletal muscles and long bones; causes
amino acids to be built into proteins; causes fat to be broken down for a source of
energy; general metabolic hormone
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Adrenocorticotropic hormone(ACTH) - controls the production of hormones in the
adrenal cortex or kidney
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→ Stimulates sperm development in testes
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✱ Posterior pituitary → Releases oxytocin and Antidiuretic hormones
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2)
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 Thyroid hormone - Major metabolic hormone; controls metabolism; contains iodine
> thyroxine (T4)
> triiodothyronine (T3)
( ) Hyperthyroidism - Too much Thyroxine and Triiodothyronine
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Diseases:
 High blood pressure - Too much Thyroid hormone
 Goiter - Too less Thyroid hormone



Calcitonin - Decreases blood calcium levels by causing its deposition on bone;
Antagonistic to parathyroid hormone
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Parathyroid Gland
 Tiny masses on the posterior of the thyroid; secretes parathyroid hormone
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> Osteoclast → bone destroying cell
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Adrenal Gland
 Sits on top of the kidneys
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5)
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Pineal Gland
 Found in the third ventricle of the brain; secretes melatonin; body’s wake and
sleep( Circadian Rythm )
 Melatonin - promotes sleep
7)
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 Thymosin - important in developing immune system; matures the blood cells
8)
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 Progesterone - produced by corpus luteum; thickens uterus along with estrogen; helps in
implantation of the embryo; brings about the menstrual cycle
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Testes
 Produces testosterone; most important androgen
 Testosterone - promotes growth and maturation of male reproductive system; required
for sperm cell production; Responsible for adult male secondary sex characteristics
NEGATIVE FEEDBACK MECHANISM
↳ The role is to decrease the production of hormones; bring things back to normal; maintain
internal balance or homeostasis
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