The Endocrine system and cell communicaiton

1. The Endocrine system and cell communicaiton AP 11/09

2. What are hormones? • From the Greek horman : to excite • Responsible for alley cats howling, teenagers moodiness, diabetes and even a caterpillar transforming into a butterfly

3. Hormones – chemical signal that is received by specific cell receptors • The Endocrine System is made up of glands that produce these hormone signals and the changes that they elicit in target cells. They “communicate” messages from one area to another, usually in an attempt to maintain homeostasis.

4. The Glands: • Exocrine – release secretions through ducts (sweat, tears, digestive juices) • Endocrine – release hormones directly to blood

5. 2 feedback loops: + and - • Negative – the response reduces the initial stimulus so it stops. • Positive – the response reinforces the stimulus and leads to a greater response.

6. 2 Main Types of Hormones: • #1 – Steroid – made from the lipid cholesterol. • They can easily cross cell membranes into cells and even nuclei. They can turn on or off sets of genes and drive protein synthesis:

7. #2 – Nonsteroid hormones: • Water soluble, generally cannot pass through cell membrane. • Binds to a cell surface receptor, which activates 2nd messengers (calcium, cAMP)

8. Paracrine signaling – local regulators between neighboring cells. • Cytokines – immune response and growth • Nitrous oxide (NO) – improves blood flow to tissues (how Viagra works). • Prostaglandins (PGs) – induce labor, contracts uterus so sperm reaches egg, induce fever and inflammation. Aspirin and ibuprofen inhibit PGs so fever and swelling reduce. Also, PGs help platelets aggregate into blood clots – but can form heart attacks. Why A and I prevent heart attacks in some people!

9. The Hypothalamus: In brain • Interacts between nervous system and endocrine. It controls the pituitary (master gland). It is our “thermostat”.

10. Pituitary – 9 hormones, 2 parts • #1 – Posterior pituitary: • Antidiuretic hormone (ADH) –makes kidneys reabsorb water. • Oxytocin – uterine contractions, milk releasing

11. Anterior pituitary: • Follicle-stimulating (FSH) – stimulates production of sperm and eggs • Luteinizing (LH) – stimulates ovaries and testes • Growth hormone (GH) – stimulates protein synthesis and growth in cells (diseases if faulty). • Prolactin – stimulates milk production in moms • Melanocyte-stimulating (MSH) – increase in skin pigrment melanin.

12. Growth hormone problems: • Too much – acromegaly • Too little - dwarfism

13. Thyroid: in the throat • Major role is regulating body’s metabolism • Makes triiodothyronine (T3 - iodine) and thyroxine (T4). These regulate cell respiration to release or slow down ATP production. • Calcitonin – lowers blood calcium levels. Ca is necessary for ALL cells, if the level falls convulsions called tetany occur and are fatal if not corrected.

14. Thyroid Disease: • Hyper and hypothyroidism – crucial in vertebrate development and maturation, so too much or little changes that. • Hyper – Graves Disease and goiter • Hypo – Cretinism, Hashimoto’s

15. Parathyroid (PTH) – raises levels of blood Calcium:

16. Adrenal Glands: • Sit on kidneys – help body deal with stress. • Makes more than 2 dozen hormones. • Epinepherine (aka adrenaline)and norepinepherine – fight or flight response. Stimulate liver to release glycogen to burn in CR – heart rate, muscles, oxygen delivery all increase. (pg 957)

17. Adrenal Diseases: • Too much – Cushing’s Syndrome • Too little – Addisons Disease

18. Pancreas: • Right side of and behind stomach. • Islets of Langerhansare clusters of cells that make insulin and glucagon. They both help keep the blood glucose level stable. • Insulin stimulates cells in liver and muscles to remove sugar from blood and store it as glycogen or fat.

19. Glucagon: stimulates liver to break down and release glucose

20. Pancreas Diseases: • Too little insulin – Diabetes mellitus, kidneys excrete glucose in urine. Organs and tissues will be damaged including coronary artery. • 2 types – Type 1 is Juvenile onset diabetes, no secretions of insulin. Control with diet and injections. • Type 2 – is adult onset. Cells are unable to respond to insulin due to body fat.

21. The Gonads – Reproductive glands: • Primary source of sex hormones. • 3 types: • 1) angrogens • 2) estrogens • 3) progestins Found in males and females but in different proportions. All babies are identical until 7 weeks.

22. Testes: Synthesize androgens • Primarily testosterone – stimulates male reproductive system. Produces sperm. • At puberty – hair patterns, lower voice, increase in muscle and bone mass.

23. Estrogens – make eggs • Most important is estradiol. Responsible for female reproductive system and secondary characteristics. • Progestins, like progesterone are involved in preparing and maintaining the uterus for an embryo. • Controlled by FSH, LH and GnRH (comlex!)

24. Eggs - • Females have about 400,000 follicles – clusters of cells surrounding a single egg. • A female does not produce any new eggs during her lifetime • Only about 400 eggs will actually be released.

25. Hormones in other life forms? • Not only found in vertebrates • Arthropods - molting, growing, reproduction • Crustaceans - pigments, movement etc.. • Plants – we’ll do a lab! Fungi – pheromones, Bacteria