THE ENDOCRINE SYSTEM

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

Example

Feedback Loop:

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

Functions of Endocrine Glands

Pineal Gland

Controls sleep and wake

cycles.

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

Hormones of the Ovaries

Estrogen – promotes growth and development of sex organs in female

Progesterone – maintains lining of the uterus

Hormone of the Testis

• Testosterone - regulates

sexual characteristics of male