The Endocrine SystemGrouping of organs that produce hormones to affect metabolic activity.

Some hormones work in tandem with other hormoneso Permissiveness- one hormone can not exert it’s full effect without another hormone

being present. Example – thyroid hormone and reproductive system hormones.o Synergism – hormone effects are amplified if the hormones are working in concert.

Glucagon and epinephrine to release glucose in bloodo Antagonism – one hormone opposing the other. Could be caused by blocking receptors

or using another method. Most hormones are regulated by a negative feedback system. As hormone levels increase, the affected organ responds and decreases the need for more hormone.

o Hormones respond to o Humoral stimuli-(think aqueous humor) chemical levels in the body’s fluidso Neural stimuli- Sympathetic and parasympathetic nervous systemo Hormonal stimulation – endocrine glands that produce hormones in response to

hormones produced by other endocrine glands. o The nervous system can modify the above factors to further regulate it.

I. Endocrine Glands - ductlessA. Pituitary – secretes at least 9 hormones. It is as big as a pea on a stalk.

a. The posterior pituitary releases neurohormones that were made by the hypothalamus (it is a storage area)

b. The anterior pituitary is composed of glandular tissue and produces at least 6 protein based hormones. They are released when the hypothalamus tells the pituitary to excrete them.

i. Four of the hormones released affect other hormone releasing glands. ii. Growth hormone – too much = gigantism (8 ft or taller), too little= pituitary

dwarfism (4 ft or less) iii. Thyroid stimulating hormone (TSH) – stimulates normal development of the

thyroid gland. iv. Adrenocorticotropic hormone (ACTH) – stimulates the adrenal cortex to secrete

corticosteroid hormones. v. Gonadotropins- Follicle stimulating Hormone (FSH), Luteinizing hormone (LH)

vi. Prolactin – stimulates the production of milk in breasts. B. Thyroid

a. Thyroid hormone – increases basal metabolic rate and body heat production. i. Hyperthyroidism- Graves disease – metabolic rate is too high, sweating,

irregular heartbeat, nervousness, etc. ii. Hypothyroidism – low metabolic rate, chills, mental sluggishness, etc. Goiter,

cretinism. b. Calcitonin – stimulates calcium uptake in bones c. Parathyroid – stimulates calcium to be released from bones into the blood.

C. AdrenalD. PinealE. Hypothalamus

a. Oxytocin- Strong stimulant for uterine contraction for childbirth, and milk ejection when prolactin is present.

b. Antidiuretic hormone – prevents urine formation. F. PancreasG. Gonads (ovaries and testes)H. PlacentaI. Tissues that have some endocrine cells

a. Adiposeb. Thymusc. Small intestine d. Stomache. Kidneys f. Heart

II. Hormones a. Can be amino acid based or steroid basedb. Eicosanoids – lipid based catalysts that are released by most cells and only affect locally.

III. How they work a. Hormones bind to their receptor on the target cell. b. Receptor activates a G protein on the inside of the cell at the membrane. c. G protein moves and attaches to Adenylate cyclase d. Adenylate cyclase converts ATP to cyclic AMPe. Cyclic AMP activates protein kinase to be a catalyst in reactions.

IV. Hormones only work if the target cell has the right receptor.