Unit 2.3 Chemical Communication

1.What is a hormone? Chemical (specifically a protein) secreted by an endocrine gland that signals a cell or an organ to do something. Some hormones are short-term (like adrenalin speeding up heart rate) and some are long term (like growth hormone) The same hormone can be secreted by multiple organs (for example, the ovaries and adrenal glands both make estrogen). Very small amounts of hormones can have very large effects. Endocrine glands = endocrine organs found in the endocrine system. Include pancreas, thymus, thyroid, pituitary gland, pineal gland, adrenal glands, ovaries and testes. Endocrine glands are found throughout the body, but are all ultimately controlled by the hypothalamus and pituitary gland in the brain

1.What is a hormone? Cont.

HormoneSecreted byFunction InsulinPancreasRegulates blood sugar levels by allowing cells to take in sugar GH (growth hormone)Anterior pituitaryStimulates growth FSH (follicle stimulating hormone) Anterior pituitaryStimulates follicle maturation GlucagonPancreasIncreases sugar levels in blood TRH (thyrotropin releasing hormone) HypothalamusTriggers pituitary gland to secrete TSH TSH (thyroid stimulating hormone) Anterior pituitaryTriggers thyroid gland to secrete T 3 /T 4 T 3 /T 4 ThyroidRegulate metabolism

2. How do hormones interact with target cells? Each hormone travels in the blood looking for target cells. Target cells have receptors that the hormone fits into, like a key. For example, a male sex hormone would only fit receptors in cells in the male sex organ and would have no effect on other cells.

3. What are examples of endocrine glands and exocrine glands in the human body? Endocrine (“secrete within”) glands Secrete hormones INSIDE the body The blood stream carries the hormones to the target cell or organ

3. What are examples of endocrine glands and exocrine glands in the human body? Cont. Exocrine (“secrete outside”) glands Secrete product into ducts to be carried outside of the body or inside an organ GlandProductLocation Sweat glandSweatSkin Cowper’s glandPre-ejaculateBase of Penis Mammary glandMilkBreast Cobelli’s glandMucusesophagus

4. How do feedback loops help regulate the action of hormones? Feedback loops keep hormones in balance and body in homeostasis. Positive feedback loops produce response that reinforces the stimulus Negative feedback loops bring body back to homeostasis When hormone levels go ABOVE homeostasis, feedback loops REDUCE hormone levels. When hormone levels drop BELOW homeostasis, feedback loops bring them back up to normal levels.

4. How do feedback loops help regulate the action of hormones?

5. How can too little or too much of a hormone lead to disease? HormoneProblem with levelsResulting disease InsulinToo lowType I Diabetes – high blood sugar Growth HormoneToo highAcromegaly -excess growth T3/T4Too highHyperthyroidism – high metabolism CortisolToo lowAddison’s Disease – weakness, fatigue. Etc.