| 29.1 What Hormones Do
The endocrine system consists of glands that secrete hormones into the bloodstream. Hormones and nerve impulses allow a person to respond to stimuli. Hormones take longer to work than nerve impulses, but they last longer. Hormones and nerves work together to form the neuroendocrine system. The pituitary gland secretes a number of hormones that regulate other endocrine glands. The endocrine system works on the principle of negative feedback. 29.2 How Hormones Work Steroid hormones bind with receptor proteins inside the cell cytoplasm, forming a complex that then attaches to the DNA, where it activates specific genes. Peptide hormones bind with appropriate receptor proteins on the cell membrane, activating the formation of cyclic AMP that acts as a second messenger inside the cell. 29.3 Glands & their Functions The adrenal glands produce adrenaline to help the body react to sudden crises and deal with long-term stress. Theyre located on top of the kidneys. The thyroid gland produces thyroxin to regulate your metabolism. Too much thyroxin increases your metabolic rate, leading to Graves disease. Too little thyroxin decreases your metabolic rate, leading to goiter. The pancreas makes 2 hormones, insulin and glucagon, to regulate your blood sugar level. The gonads (ovaries & testes) produce sex hormones. The pineal gland makes melatonin. Prostaglandins are small glands located throughout the body. When not enough insulin is produced, blood sugar levels can get too high (diabetes mellitus). Anabolic steroids are a dangerous, illegal form of testosterone. |