The document discusses the endocrine system and how it regulates bodily functions through hormones secreted into the bloodstream. It explains that the endocrine system works slowly and hormones can last a long time in the blood compared to the nervous system which works faster through nerve impulses. Some of the major glands and hormones discussed include the adrenal gland which secretes adrenaline to prepare the body for fight or flight, the thyroid gland which controls metabolism through thyroxine, and the pituitary gland which influences many other glands.