The Endocrine System Endocrine Glands Endocrine glands release

The Endocrine System

Endocrine Glands • Endocrine glands release hormones • Hormones: chemicals that circulate • through the body to regulate the metabolic functions of other cells in the body The cells affected by a hormone are called its target cells Target cells must have specific protein receptors for the hormone so that the hormone can bind and do its job

Process of hormone release and action Stimulus Hormone is released Hormone travels to target cells Desired effect is achieved Hormone binds to receptor on target cell

Hormones we have mentioned in class… • • Calcitonin Parathyroid hormone (PTH) Growth hormone Estrogen Testosterone Epinephrine (adrenalin) Erythropoietin

Classes of Hormones 2 main types: • Steroid (made from cholesterol) - bind directly to DNA to exert their effects through transcription and translation (ex. Testosterone, estrogen, thyroxine) • Amino acid based (made from amino acids) - bind to a receptor on a cell’s membrane to exert its effect via a 2 nd messenger molecule (ex. Growth hormone, epinephrine, insulin)

Endocrine Gland Stimuli • Neural - nervous system stimulates • • release of hormone Humoral - a substance in the blood stimulates release of a hormone (ex. PTH and blood calcium) Hormonal - a hormone is released for the purpose of stimulating another gland to release a hormone

Hormonal Blood Sugar Regulation • Insulin and glucagon • • • (both released from pancreas) regulate blood sugar Insulin lowers blood sugar if it is too high Glucagon raises blood sugar if it is too low Carbohydrates stimulate insulin release (fats and proteins have little effect on insulin)