By Nathan Aleynick AP Biology Period 1 Ms. Straubel

 The endocrine system in charge of producing and distributing hormones through out the body.  Hormones are used by the body to bring about long term changes (Ex. Puberty, Ovulation) by bonding to their target cells.  Hormones are responsible for long distance communication within the body.

 The endocrine system works with the nervous system to keep the body in homeostasis.  Balance is maintained using feedback loops.  Feedback loops come in two forms:  Negative: Most prevalent of the two. The nervous system indicates an imbalance in the body, and the endocrine works to reverse the problem to maintain balance (Ex. High blood sugar is reversed with insulin).  Positive: Less prevalent of the two. The nervous system indicates that a change is beneficial and the endocrine system works to enhance the change (Ex. Uterine contractions are enhanced by the release of oxytocin).

 There are three different kinds of molecules that could be hormones:  Protein/Peptide hormones  Anime (derived from amino acids) hormones  Steroid hormones  Hormones are secreted by a gland, enter the bloodstream and then bind to their target cells.  Once the hormone is bonded to their target cell, a response is triggered.

 Local regulators work similarly to hormones except that they travel between neighboring cells rather than long distance.  Local regulators convey messages through what is called paracrine signaling.  Ex. Nitric oxide is released by endothelial cells when O 2 levels are low, causing other endothelial cells to relax and increase blood flow.

 No hormones are produced by the posterior pituitary gland.  Rather, it stores and secretes the hormones produced by the hypothalamus.

 The hypothalamus produces hormones for the posterior pituitary gland.  Oxytocin: A peptide hormone that stimulates the contraction of the uterus and mammary glands.  Antidiuretic hormone (ADH): A peptide hormone that signals the kidneys to retain water.

 Growth hormone (GH): A protein hormone that stimulates growth and metabolic functions.  Prolactin (PRL): A protein hormone that stimulates the production and secretion of milk.  Follicle-stimulating hormone (FSH): A glycoprotein that stimulates the production of sperm and ova.

 Luteinizing hormone (LH): A glycoprotein that stimulates the ovaries and the testes.  Thyroid-stimulating hormone (TSH): A glycoprotein that stimulates the thyroid gland to release its hormones.  Adrenocorticotropic hormone (ACTH): A peptide hormone that stimulates the adrenal cortex to secrete glucocorticoids.

 Triiodothyronine (T 3 ) and Thyroxine (T 4 ): Amine hormones that stimulate and maintain metabolic processes.  Calcitonin: A peptide hormone that lowers the level of calcium in the blood.

 Parathyroid hormone (PTH): A peptide hormone that raises the level of calcium in the blood.

 Insulin: A protein hormone that lowers the blood glucose level.  Glucagon: A protein hormone that raises the blood glucose level.

 Epinephrine/Norepinephrine: An amine hormone that raises the blood glucose level, increases the body’s metabolic activities and constricts certain blood vessels.

 Glucocorticoids: A steroid hormone that raises the blood glucose level.  Mineralocorticoids: A steroid hormone that increases the absorption of Na + and increase the excretion of K + from the kidneys.

 Androgens: A steroid hormone that aids in the production of sperm and helps develop secondary male sex characteristics.

 Estrogens: Steroid hormones that stimulate the development of the uterine lining and helps develop secondary female sex characteristics.  Progesterone: A steroid hormone that promotes the growth of the uterine lining.

 Melatonin: An amine hormone that helps control biological rhythms (Ex. Sleep cycle).

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