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The Endocrine System

The Endocrine System. Ch 34 – Parrot Ch 45 – Advanced Biology. I. The Endocrine System. A. Control Pathways and Feedback Loops 1. Components a. stimulus b. receptor protein c. chemical messengers d. target cells e. response. 2. Control Pathways a. Simple Endocrine Pathway.

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The Endocrine System

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  1. The Endocrine System Ch 34 – Parrot Ch 45 – Advanced Biology

  2. I. The Endocrine System A. Control Pathways and Feedback Loops 1. Components a. stimulus b. receptor protein c. chemical messengers d. target cells e. response

  3. 2. Control Pathways a. Simple Endocrine Pathway

  4. b. Simple Neurohormone Pathway

  5. c. Simple Neuroendocrine Pathway

  6. B. Components of Endocrine System 1. Hormones a. chemical messengers released into extracellular fluid in one part of the body, travel through the circulatory system, affects other parts of the body b. communicates regulatory messages c. binds to specific chemical receptors on cell membranes or within cells

  7. d. Travels throughout the body, but only affects target cells 1) cells that have receptors for a particular hormone e. body’s response to hormones is slower and longer lasting than to the nervous system f. Most endocrine functions depend upon two opposing hormones

  8. 2. Glands a. an organ that produces and releases a substance or secretion b. exocrine glands 1) release their secretions through ducts either out of body to digestive system c. endocrine glands 1) release hormones to blood

  9. 3. Local Regulators a. convey messages between neighboring cells within seconds or milliseconds b. some have cell-surface receptors and some have intracellular receptors

  10. c. Types of chemical compounds acting as local regulators 1) many neurotransmitters 2) cytokines – immune system 3) growth factors 4) nitric oxide a) dilate and constrict blood vessels b) kills some bacteria c) kills some cancer cells

  11. 5) prostaglandins a) cause uterus to contract b) help induce fever, inflammation, and intensify pain c) regulate aggregation of platelets d) dilate and constrict blood vessels

  12. C. Hormone Action

  13. C. Hormone Action 1. Steroid Hormones a. produced from lipid cholesterol b. not water soluble – hydrophobic c. steroids usually pass through the lipid bi-layers of cell membrane and to the nucleus where it changes the pattern of gene expression

  14. d. Steroid action A steroid hormone enters a cell by passing directly across the cell membrane Once inside, the hormone binds to a receptor (found only in the hormone’s target cells) and forms a hormone-receptor complex

  15. 3) The hormone-receptor complex enters the nucleus of the cell, where it binds to regions of DNA that control gene expression 4) This binding initiates the transcription of specific genes to messenger RNA (mRNA)

  16. 5) The mRNA moves into cytoplasm and directs protein synthesis e. Steroids are powerful and long lasting

  17. 2. Non-steroid Hormones a. include proteins, small peptides, and modified amino acids or amines b. water soluble c. bind to receptors on cell membranes and cause the release of secondary messengers that affect cell activities

  18. d. Nonsteroid action 1) a nonsteroid hormone binds to receptors on the cell membrane 2) the binding of the hormone activates enzymes on the inner surface membrane

  19. 3) These enzymes release secondary messengers such as calcium ions, nucleotides, and even fatty acids to relay the hormone’s message within the cell 4) These secondary messengers can activate or inhibit a wide range of cell activities

  20. II. Glands of the Endocrine System A. Functions of Major Endocrine Glands 1. Pituitary Gland a. secretes hormones that directly regulate many body functions or control the actions of other endocrine glands b. anterior pituitary gland c. posterior pituitary gland

  21. 2. Hypothalamus a. attached to posterior pituitary gland b. links CNS and endocrine system c. controls the secretions of the pituitary gland d. activities influenced by 1) the level of hormones and other substances in the blood 2) sensory information from CNS

  22. e. Hormones 1) antidiuretic hormone a) stimulates kidneys to absorb water 2) oxytocin a) stimulates contractions during childbirth

  23. 3) releasing hormones a) hormones released into the anterior pituitary gland causing it to release hormones f. Tropic hormone 1) a hormone that has another endocrine gland as a target

  24. 3. Adrenal gland a. release hormones to help body deal with stress

  25. b. corticosteroids 1) produced by adrenal cortex 2) more than two dozen hormones a) aldosterone 1 – regulates blood volume and pressure b) cortisol 1 – helps control rate of metabolism of carbohydrates, fats, and proteins

  26. c. Adrenal medulla 1) sympathetic nervous system causes release of hormones a) epinephrine (adrenaline) or norepinephrine 1 – increase heart rate, increase blood pressure, widen air passages, causes release of extra glucose 2 – example of how one chemical signal can have different effects

  27. 4. Pancreas a. exocrine gland 1) releases digestive enzymes b. endocrine gland 1) releases insulin and glycagon from “islets of Langerhans” a) beta (β) cells release insulin b) alpha (α) cells release glucagon

  28. 2) Insulin stimulates cells to take glucose out of blood a) liver and skeletal muscles store glucose as glycogen 1 – glycogen is a polysaccharide (it is the animal equivalent of starch in plants) b) in fat tissue, glucose is converted to lipids

  29. 3) When blood glucose drops, glycagon is released from pancreas a) stimulates liver and skeletal muscle cells to break down glycogen and release glucose into blood b) causes fat cells to convert lipids into glucose

  30. Type I Diabetes Mellitus 1. Autoimmune disorder 2. body’s immune system kills beta (β) cells 3. thus, insulin is not produced Type II Diabetes Mellitus 1. Body cells do not respond to insulin 2. Because insulin receptors do not respond properly 3. Incidence increasing because of obesity

  31. 5. Thyroid and Parathyroid Glands a. thyroxine 1) increases metabolic rate of cells – cells become more active, use more energy, and produce more heat 2) iodine is needed for thyroxine production

  32. 3) Hyperthyroidism a) too much thyroxine b) nervousness, elevated body temperature, increased blood pressure, weight loss 4) Hypothyroidism a) too little thyroxine b) low body temperature, lack of energy, weight gain

  33. b. Calcitonin 1) reduces blood calcium levels 2) signals kidneys to reabsorb less calcium from filtrate, inhibits calcium absorption in small intestine and promotes calcium absorption into bones

  34. c. Parthyroid hormone (PTH) 1) released by 4 parathyroid glands on the back of the thyroid 2) increases calcium levels in the blood 3) promotes release of calcium from bone, reabsorption of calcium in kidneys and increase uptake of calcium from small intestine 4) promotes proper nerve and muscle function and proper bone structure

  35. 6. Reproductive Glands a. gonads 1) testes and ovaries 2) produce gametes (egg and sperm) 3) secrete sex hormones a) ovaries – secrete estrogens b) testes – secrete testosterone

  36. B. Control of Endocrine Glands 1. the endocrine system is regulated by feedback mechanisms that function to maintain homeostasis

  37. 2. Controlling Metabolism 1 – hypothalamus senses that thyroxine levels in blood are low 2 – hypothalamus releases thyrotropin-releasing hormone (TRH) 3 – TRH stimulates anterior pituitary gland to secrete thyroid-stimulating hormone (TSH) 4 – thyroid-stimulating hormone (TSH) stimulates thyroid gland to release thyroxine 5 – as thyroxine levels increase, thyrotropin-releasing hormone (TRH) and thyroid-stimulating hormone (TSH) release decreases 6 – release of thyroxine stops

  38. 3. Controlling Body Temperature 1 – hypothalamus senses that core body temperature is low 2 – hypothalamus releases thyrotropin-releasing hormone (TRH) 3 – TRH stimulates anterior pituitary gland to secrete thyroid-stimulating hormone (TSH) 4 – thyroid-stimulating hormone (TSH) stimulates thyroid gland to release thyroxine 5 – thyroxine increases oxygen consumption and increases cellular metabolism/cellular respiration 6 – the increase in metabolic activity, increase body temperature

  39. 4. Maintaining Water Balance 1 - concentration of solutes in blood increases 2 – hypothalamus signals posterior pituitary gland 3 – posterior pituitary gland releases more antidiuretic hormone (ADH) 4 – more antidiuretic hormone (ADH) goes to kidneys via the blood 5 – kidneys slow down water removal 6 – you realize that you are thirsty and take a drink 7 – water is quickly absorbed into blood 8 – solute concentration in blood decreases 9 – hypothalamus signals posterior pituitary gland 10 – pituitary gland releases less antidiuretic hormone (ADH) 11 – less ADH goes to kidneys via the blood 12 – kidneys increase amount of water removed from blood

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