1. u Chapter 45 ~ Chemical Signals in Animals

2. Objectives u 1. Outline the two ways hormones affect target organs u 2. Draw and annotate both positive and negative feedback in the regulation of homeostasis by hormones. u 3. Explain the control of blood glucose concentration, including the roles of glucagon, insulin and ά and ß cells in the pancreatic islets. u 4. Distinguish between type I and type II diabetes. u 5. List the glands of the endocrine system, name the hormones produced and state their functions.

3. Regulatory systems u Hormone~ chemical signal secreted into body fluids (blood) communicating regulatory messages with in the body. –Produced and secreted by cells of endocrine glands. t Transported in the bloodstream but act only at specific sites called “Target Organs” –Modified a.a. tyrosine (ex. Thyroxin from the thyroid gland), peptides (ex. ADH) or steroid molecules (ex. Sex hormones) –Help control and coordinate body activities –Only circulate in blood for short periods and is broken down in the liver and excreted by the kidneys. t Long acting hormones must be secreted continuously to be effective u Target cells~ body cells that respond to hormones u Endocrine system/glands~ hormone secreting system/glands (ductless); exocrine glands secrete chemicals (sweat, mucus, enzymes) through ducts

5. Review Homeostasis u How do organisms respond to environmental changes? –Regulator – an animal that is able to maintain a constant internal environment t Mammals & birds – can maintain a constant internal temperature over wide range of external temperatures. –Non-regulators – an animal that is unable to maintain a constant internal environment t reptiles u Mammals, regulation of body temperature, blood sugar level, and the amounts of water and ions in blood and tissue fluid are regulated by negative feedback. u Detectors: specialized cells in the brain or other organs u Effectors: skin, liver and kidneys –Information past between them via nerves system or hormones or both

6. Explain that homeostasis involves monitoring levels of variables and correcting changes in levels by negative feedback mechanisms. (previous objective) u Negative feedback is the type of control in which conditions being regulated are brought back to a set value as soon as it is detected that they have deviated from it. Detector: Measures level Of the variable Control unit: Level of operation is set here, and Information from detector received and compared with set value, and commands to effector dispatched from here Effector: Brings about a second change to system (in opposite direction to the input) Output: Condition restored to set value Input: Change to the system

7. Positive vs. Negative u Determine the following: u The chlorine level of a swimming pool decreases when the chlorinator is turned off. –positive u An increase in blood sugar concentration increases the amount of hormones that stores sugar as glycogen. –negative u A decrease in calcium concentration increases the amount of the hormone that releases calcium from the bone. –negative u There is a decrease in water pressure when the faucet is slowly turned off –positive u A decrease in blood sugar concentration increases the amount of the hormone that converts glycogen to sugar –negative

8. Draw and annotate both positive and negative feedback in the regulation of homeostasis by hormones. u Neurosecretory cells~ actual cells that secrete hormones u Many chemicals act as both hormones and nerves system signals –Ex. Epinephrine t Fight or flight hormone t A neurotransmitter in nervous system u Feedback mechanisms ~ negative and positive

10. Positive feedback

11. u What type of feed back is “Baby suckles – sensory cells – nerves signal the brain – triggers a hormone release – causes milk to secrete” –Positive feed back u What type of feedback maintains homeostasis, many endocrine and nervous mechanisms –Negative feedback

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13. u Hormones in mollusks tell it to release its eggs but inhibit anything that would interfere with reproduction u Insects molt

14. Local regulators: cells adjacent to or near point of secretion u Growth factors ~ peptides and proteins for cell proliferation u Nitric oxide (NO) ~ gas; local regulator; neurotransmitter; cell destruction (some bacteria and cancer cells); vessel dilation u Prostaglandins ~ modified fatty acids secreted by placenta and immune system; also found in semen; can cause pain to tell you something is wrong with your body, something harmful is happening (aspirin or ibuprofen inhibit prostaglandins) –PGE – relax –PGF - contract

15. Outline the two ways hormones affect target organs u Hormones –blood stream – all cells in body u Alter the metabolic reactions only in certain cells – must have specific receptor molecules (no receptor molecules=no effect on cell) u Hormones impact differently depending on chemical composition of hormone: –1. Steroid hormones – cross plasma membrane, causes activation of a specific gene in nucleus. t Trigger synthesis of particular protein (enzyme) which brings about change –2. Protein, peptide or amine hormones – binds to receptor on membrane of target cell. (remains on outside of cell). Causes secondary messenger on inside of plasma membrane. This causes activation of existing protein which then brings about specific changes in metabolism

16. Steroid: steroid Peptide: peptidesteroidpeptide

17. u Reception of the signal molecule binds to a specific receptor protein, which is either built into the plasma membrane of the target cell or located inside the target cell

18. Mode of Action: Chemical Signaling u 1- Plasma membrane reception (peptide hormones) signal-transduction pathways (neurotransmitters, growth factors, ADH, FSH, LH, most hormones) u 2- Cell nucleus reception steroid hormones, thyroid hormones, estrogen, progesterone, testosterone, some local regulators

19. Signal transduction pathway u Chemical signals may bind to receptors in the plasma membranes of certain cells and this triggers a signal transduction pathway, consists of a series of molecular events that initiates a response to the signal.

20. Same signals can bring about different responses in different target cells.

21. u Why is it that some body cells respond differently to the same peptide hormones? u A. different target cells have different genes. u B. each cell knows how it fits into the body’s master plan u C. a target cell’s response is determined by the product of a signal transduction pathway u D. the circulatory system regulates responses to hormones by routing the hormones to specific targets. u E. the hormone is chemically altered in different ways as it travels through the circulatory system u Answer C

22. Vertebrate Endocrine System u Hormones can affect one tissue, a few tissues, or most of the tissues in the body (like sex hormones), or they may act as tropic hormones, which have other endocrine glands as their targets.

23. Vertebrate Endocrine System u Tropic hormones ~ a hormone that has another endocrine gland as a target u Hypothalamus~pituitary u Pituitary gland u Pineal gland u Thyroid gland u Parathyroid glands u Thymus u Adrenal glands u Pancreas u Gonads (ovary, testis)

24. u List the glands of the endocrine system, name the hormones produced and state their functions.

27. The hypothalamus & pituitary, I u Releasing and inhibiting hormones u Anterior pituitary: u Growth (GH)~bones √gigantism/dwarfism √acromegaly u Prolactin (PRL)~mammary glands; milk production u Follicle-stimulating (FSH) & u Luteinizing (LH)~ovaries/testes u Thyroid-stimulating (TSH)~ thyroid u Adrenocorticotropic (ACTH)~ adrenal cortex u Melanocyte-stimulating (MSH) u Endorphins~natural ‘opiates’; brain pain receptors

28. The pituitary, II u The posterior pituitary: u Oxytocin ~ uterine and mammary gland cell contraction u Antidiuretic (ADH )~ retention of water by kidneys

29. The pineal, thyroid, & parathyroid u Melatonin ~ pineal gland; biological rhythms u Thyroid hormones: Calcitonin~ lowers blood calcium Thyroxine~ metabolic processes u Parathyroid (PTH)~ raises blood calcium –(tetany – several muscle spasms)

30. The pancreas u Islets of Langerhans u Alpha cells: glucagon~ raises blood glucose levels u Beta cells: insulin~ lowers blood glucose levels u Type I diabetes mellitus (insulin-dependent; autoimmune disorder) u Type II diabetes mellitus (non-insulin-dependent; reduced responsiveness in insulin targets)

31. The adrenal glands u Adrenal medulla (catecholamines): epinephrine & norepinephrine~ increase basal metabolic rate (blood glucose and pressure) u Adrenal cortex (corticosteroids): glucocorticoids (cortisol)~ raise blood glucose mineralocorticoids (aldosterone)~ reabsorption of Na+ and K+

32. The gonads u Steroid hormones: –precursor is cholesterol u androgens –(testosterone)~ sperm formation; male secondary sex characteristics; gonadotropin u estrogens –(estradiol)~uterine lining growth; female secondary sex characteristics; gonadotropin u progestins –(progesterone)~uterine lining growth

33. Explain the control of blood glucose concentration, including the roles of glucagon, insulin and ά and ß cells in the pancreatic islets. u Normal levels of glucose is 90mg in every 100cm3 of blood –Ex. Extended period without food or prolonged physical activity can fall to 70 mg –Ex. Eating a meal heavy in carbs can raise the glucose in the blood to 150 mg

34. Cont. Maintenance important for 2 reasons u 1. respiration continuous process in all cells, to maintain metabolism cells need regular supply of glucose u Most cells hold reserves in glycogen converted to glucose during prolonged physical activity u Reserves quickly used up u Brain no reserves u Falls 60mg – hypoglycemia – faint, convulsions, coma u 2. hyperglycemia – abnormally high concentration of blood glucose u This lowers water potential of blood plasma, water drawn into cells through osmosis from tissues causes blood volume to increase then excreted in kidney – body is dehydrated, circulation deprived of fluid. u Blood pressure can’t be maintained

35. Cont. u Responses to high blood glucose levels u B cells in pancreatic islets produce insulin u Insulin stimulates the liver and muscle cells to absorb glucose from the blood and convert it to glycogen. Granules of glycogen are stored in the cytoplasm of these cells. Other cells are stimulated to absorb glucose and use it in cell respiration instead of fat. These processes lower the blood glucose level u Responses to low blood glucose levels u A cells in the pancreatic islets produce glucagon. u Glucagon stimulates liver cells to break glycogen down into glucose and release the glucose into the blood u This raises the blood glucose level.

36. Glucose regulation by negative feedback Starvation, physical activity Islet of Langerhans of pancreas Secreted by ά cells Glycogen and a.a. are converted into glucose Rise in blood glucose Rise after meal Glucagon secretion stops Islet of Langerhans of pancreas Insulin secreted by ß cells Muscle and other tissues take glucose and converts it to glycogen increases fatty acids, fat and cell respiration Insulin secretion stops

37. Blood circulation connects all organs directly or indirectly glucose glycogen Muscles can import glucose but do not export it glucose glycogen Most tissues can import or export glucose glucose Brain cells import glucose as required but do not store glycogen Small intestine glucose absorption Liver imports glucose when blood level is high; exports glucose when blood glucose level is low Glucose = a.a or glycogen or fat Pancreas contains special cells of two types that are sensitive to the level of sugar in the blood ß cells secrete insulin when glucose level is high, insulin causes lowering of blood glucose level ά cells secrete glucagon when glucose level is low, glucagon causes raising of blood glucose level

38. Distinguish between type I and type II diabetes. u Type I u ‘early onset diabetes’ u Below age of 20 u Due to destruction of ß cells on the islet of Langerhans by the body’s own immune system u Symptoms –Constant thirst –Undiminished hunger –Excessive urination –Insulin injections are used to control glucose levels –Diet itself cannot control this condition u Treatment –Injection of insulin into blood stream daily –Regular measurement of blood glucose level u Type II u ‘late onset diabetes’ u 90% of all cases of diabetes are this type u Common in people over 40 years, overweight, increasing effect on human societies around the world, including young people and children in developing countries, due to poor diet u Symptoms –Mild – sufferers usually have sufficient blood insulin, but insulin receptors on cells have become defective –Usually after childhood –Target cells insensitive to insulin u Treatment –Largely by diet alone (low carb. diets) –Insulin injections are not usually needed

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