Chemical Signals in Animals

1. Chemical Signals in Animals Chapter 45

2. 2 communication systems in body. • 1Nervous system, 2endocrine system. • Endocrine system - glands and tissues that secrete hormones, chemical messengers produced by cells to act on other cells.

3. http://scienceblogs.com/clock/upload/2006/06/endocrine%20system.jpghttp://scienceblogs.com/clock/upload/2006/06/endocrine%20system.jpg

4. Some hormones act on nearby cells (paracrine signals) others on same cells that made them (autocrine signal). • Signals in endocrine system take longer to reach destination (carried by blood), longer lasting than nervous impulses.

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6. Endocrine glands secrete hormones directly into bloodstream. • Exocrine secretions do not contain hormones; released through ducts into body compartment. • Example - pancreas in digestion.

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8. Hormones classified into 2 groups: steroid hormones, peptide hormones. • Both must bind to protein receptor on target cell, peptide hormones must bind to receptors on cell surface since they cannot cross membrane. • Causes signal to be transmitted to inside of cell.

9. Signal can activate 2nd messengers, which amplify signal and alter cell activities - called signal transduction cascade because process amplified as it continues down path.

11. Steroid hormones usually smaller and can pass through membrane. • Most come from cholesterol and usually enter nucleus of cell, altering protein synthesis (transcription). • Steroid hormones not stored, unlike protein hormones - need to be regulated in order to be secreted.

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13. Endocrine glands • Regulation of production and secretion of hormones done through feedback loop. • Some hormones regulate release of other hormones.

15. 1Hypothalamus and pituitary – found in forebrain, located above pituitary gland. • Pituitary has 2 parts: anterior pituitary, posterior pituitary. • Posterior - vasopressin (antidiuretic hormone or ADH) - acts on kidney to conserve water; oxytocin - aids in childbirth.

16. http://www.becomehealthynow.com/images/organs/nervous/glakgar_pit_hypothalamus.jpghttp://www.becomehealthynow.com/images/organs/nervous/glakgar_pit_hypothalamus.jpg

17. Hormones made in hypothalamus, pass through posterior pituitary - secreted. • Anterior pituitary regulated by hypothalamus through portal blood circulation - carries blood directly from hypothalamus to pituitary.

18. http://www.brainexplorer.org/brain-images/hypothalamus.jpg

19. Hypothalamus stimulated - releasing factors into portal blood circulation carried to pituitary - cause release of hormone from anterior pituitary. • Growth hormone promotes growth in body tissues.

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21. Thyroid stimulating hormone (TSH) stimulates thyroid to secrete thyroxin. • Adrenocorticotrophic hormone (ACTH) stimulates adrenal cortex to secrete corticosteroids in response to stress.

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23. Prolactin - responsible for milk production. • Follicle-stimulating hormone (FSH) promotes maturation of seminiferous tubules in males, ovaries in females. • Luteinizing hormone (LH) - promotes testes to secrete testosterone in males; causes ovulation of egg in females.

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25. Endorphins act on central nervous system to block pain signaling (like opiates). • 2Thyroid gland – thyroxine accelerates metabolism. • Person deficient can develop goiter, lethargy, obesity. • Hyperthyroidism causes profuse sweating, weight loss, increased BMR.

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27. Thyroxine secretion stimulated by hypothalamus in response to environment (like cold), acts on thyroid gland. • Thyroid gland also produces calcitonin - regulates calcium concentration in blood.

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29. Calcitonin increases stimulates bone formation, decreases bone destruction. • Calcitonin opposed by parathyroid hormone. • 3Parathyroid glands – located on backside of thyroid gland, secretes parathyroid hormone - regulates calcium, phosphate balance between blood, other tissue.

30. http://cyber.law.harvard.edu/blogs/static/heydan/parathyroid.jpghttp://cyber.law.harvard.edu/blogs/static/heydan/parathyroid.jpg

31. Increased parathyroid hormone increase bone release of calcium. • Decreased calcium in blood causes secretion of parathyroid hormone which increases activity of osteoclasts (bone breaking cells) - remodels bones to release calcium.

32. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

33. 4Pancreas – performs both exocrine, endocrine functions. • Endocrine function occurs in islets of Langerhans which contain alpha and beta cells that secrete glucagon and insulin. • Insulin stimulates muscles and other cells to release glucose from blood.

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35. Causes muscles and liver to convert glucose to glycogen (storage form of glucose). • Glucagon responds to low levels of blood glucose - stimulates breakdown of glycogen to glucose. • Diabetics cannot control levels of insulin.

37. 5Adrenal glands – found on top of kidneys, consist of adrenal cortex on exterior + adrenal medulla on inside of gland. • Medulla responsible for epinephrine and norepinephrine in response to stress.

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39. Epinephrine responsible for adrenaline release as well as causing blood to shunt away from skin, digestive organs, kidneys; increases blood flow to heart, brain, skeletal muscle. • Also increases metabolic activity.

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41. Cortex responsible for secretion of corticosteroids - regulated by nervous system in response to stress, 3 types. • AGlucocorticoids help to raise blood glucose levels. • High doses help in inflammation response.

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43. BMineral corticoids - promote reabsorption of Na+, excretion of K by kidneys. • CSex hormones – androgens responsible in part for female sex drive.

45. 6Ovaries, Testes - testes produce testosterone in males, estrogen and progesterone in females. • 7th week of development, information on Y chromosome (if present) starts to produce testosterone. • Absent - female hormones are produced.

47. ATestes – releases androgens (like testosterone) responsible for production of sperm and secondary male sex characteristics. • BOvaries – secrete estrogen and progesterone.

48. http://www.redhotflush.co.uk/images/cartoons/hormones.jpg

49. 1Estrogen responsible for stimulating lining of uterus to grow and secondary sex characteristics of females. • 2Progesterone responsible for promoting lining of uterus to grow.

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