are chemical messengers secreted by glands. Exocrine glands, such as sweat glands, secrete fluids through ducts. glands secrete hormones directly into the bloodstream. The gland plays an important role in puberty and growth. Epinephrine, triggering the "fight or flight" response, is produced by the glands, which sit on top of the kidneys. Most glands that secrete hormones operate using feedback mechanisms. When hormone concentrations are high, the gland will produce of the hormone. Many cells produce chemicals called , hormone-like substances that impact inflammation and reproduction. The gland that helps regulate growth, body temperature, and the level of calcium in the blood is called the . Describe the function and compare steroidal and nonsteroidal hormones. How does each type of hormone interact with the cell? What other molecules are required for or involved in their function? ANSWERS:

1. Hormones

2. endocrine

3. pituitary

4. adrenal

5. less

6. prostaglandins

7. thyroid

8. Steroidal hormones enter the cell directly and interact with DNA inside the nucleus. These hormones change gene expression, affecting the RNA that is produced and the proteins that are translated in a cell. Nonsteroid hormones do not enter the cell. Instead, they bind to specific receptors on the outside of the cell membrane. This triggers molecules called secondary messengers, such as cAMP, to begin their work of relaying information in the cell, where other chemicals, messengers, and proteins are involved to create a cellular response.