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Overview of the Endocrine System
Made up of glands that release hormones into the bloodstream
◦ Hormones are chemical "messengers" that control numerous body functions
Functions:
omaintenance of homeostasis (keeping a balanced environment inside the body)
oregulation of growth and development
Transport of Hormones
Once released from an endocrine gland
hormones are transported throughout the
body by the bloodstream
A given hormone usually affects only a limited
number of cells called target cells
Target cells have the appropriate receptor for
the hormone to attach to
Homeostasis is maintained though a
system called negative feedback
when the amount of a particular
hormone in the blood reaches a certain
level, the endocrine system sends signals
that stop the release of that hormone
Sometimes a hormone with an opposing
function may be released, if needed
Major Glands of the Endocrine System
Pineal and pituitary are in the brain
Parathyroid glands sit on the thyroid in the neck
Thymus is found behind the breastbone
Adrenals sit on the kidneys
Pancreas is in the abdomen
Testes are in the scrotum and ovaries are in the hip area
Hormones of the Pituitary Growth Hormone
(GH)- growth hormone; helps fat be used for energy
Thyroid-stimulating Hormone (TSH)-stimulates growth of the thyroid gland
Adrenocorticotropic Hormone (ACTH)-stimulates growth of the adrenal gland
Follicle stimulating Hormone (FSH) – growth of the ovarian follicles, production of estrogen in females; & production of sperm in males
Luteinizing Hormone (LH) –stimulates ovulation and produces progesterone in females
Oxytocin – released during childbirth; causes contraction of the uterus
Hormone of the Pineal Gland
◦ Melatonin- released at night
to make you sleepy; replenished
during the day
Regulates the circadian rhythm
(24-hour biological clock)
Hormones of the Thyroid Gland
◦ Thyroxine – increases metabolic rate; regulates growth and development
Requires iodine to be produced, which is found in foods and iodized salt
◦ Calcitonin – lowers blood calcium by accelerating storage in bones
99% of calcium in the body is stored in bones, necessary for blood clotting, muscle contraction, and holding cells together
Hormone of the Parathyroid
Parathormone (PTH) – raises
blood calcium (opposite effect of
calcitonin) to maintain proper
levels of circulating calcium
Hormones of the Adrenal Gland
Epinephrine (adrenaline) & Norepinephrine released
in emergency or stress situations
to raise blood glucose levels and
prepare the body for the
“fight or flight” response
Cortisol: “stress hormone”that raises blood glucose by
stimulating the breakdown of
proteins
◦ Too much suppresses the
immune system
Hormones of the Pancreas
Insulin – lowers blood glucose;
promotes storage of glycogen in
liver and muscles
Glucagon– raises blood glucose
Hormone of the Thymus Gland
Thymosin - stimulates
production of antibodies in early
years