The endocrine system

1. The endocrinesystem Honors Anatomy & Physiology

2. Endocrine vs nervoussystem • act together to coordinate body’s activities • both: • use chemical messengers to communicate cell to cell • major function: homeostasis • endocrine: slower response time • hormones transported thru circulatory system • target cells (any cell with hormone receptor) anywhere in body • nervous: quicker conduction of signals • neurotransmitters • act on cells close by

3. Glands • no ducts • secretions released and diffuse into blood capillaries • have ducts • secretions released onto surface • example: sweat glands, salivary glands Endocrine Exocrine

4. 2 types of hormones • bind to protein receptors in cell membranes (do not enter cell) • receptor-hormone activate enzyme in cytoplasm  series of reactions result in cell response • enter cell & bind to receptor in cytoplasm or nucleus • Activates transcription of gene  protein produced • generally action slower than peptide hormone Peptide Steroid

6. Endocrine system

7. hypothalamus • part of brain • secretes “releasing” hormones that act on pituitary gland • axons that store the 2 posterior pituitary hormones end there

9. Pituitary gland • 2 lobes: posterior & anterior

10. Negative Feedback Inhibition

11. Thyroid Gland • stimulated by TSH • secretes thyroxin (T4) and triiodothyronine (T3) • (-) feedback inhibition • both have similar effects on target cells

12. hypothyroidism • Thyroid produces too little hormone • several causes: Hashimoto’s autoimmune/ lack of Iodine in diet  goiter (enlargement of thyroid due to increased TSH stimulation • Symptoms: • Adults: lethargy, weight gain, anovulatory cycles • Infants:cretinism: dwarfism, low IQ, failure to reach sexual maturity

13. Goiter

14. hyperthyroidism • excessive secretion of thyroid hormones

15. Parathyroid Glands • 4 small glands embedded in posterior surface of thyroid gland • secrete: parathyroid hormone (PTH) • regulated by serum Ca++ levels • actions: • stimulates removal of Ca++ from bone • increases kidney tubules reabsorption of Ca++ • activates vit D which enhances Ca++ absorption from food

17. thymus • upper thorax, posterior to sternum • largest in infants, decreases as we age • produces: thymosin – programs T cells

18. Adrenal gland

19. Adrenal Cortex • outer layer • produces 2 kinds of steroid hormones • Glucocorticoids • major 1 – cortisol: • reduces swelling by inhibiting immune system/ raises serum glucose (stimulates liver to make glucose from proteins or lipids • Mineralocorticoids • major 1- aldosterone • acts on kidney to promote absorption of Na+ & excretion of K+

20. pancreas • Insulin • protein • reduces blood glucose by increasing entry of glucose into cells/making glycogen in hepatocytes • regulated by blood glucose levels • Glucagon • protein • raises blood glucose by acting on glycogen stores in liver • regulated by blood glucose levels

22. testes • paired oval organs suspended in scrotum • site of: • spermatogenesis • production of androgens: • Testosterone major one • made by interstitial cells/stimulated by FSH & LH • produces male 2◦ sex characteristics in puberty • promotes growth & maturation of reproductive system organs • increases libido

24. ovaries • paired, almond-shaped organs in pelvic cavity • produce ova • release: estrogens & progesterone • begin functioning in puberty in response to anterior pituitary gonadotrophins

25. estrogens • Estrone &Estradiol made by follicle where ova is maturing • stimulate: • development of 2◦ sex characteristics • work with progesterone to prepare uterine lining for implantation • help maintain pregnancy & prepare breasts to lactate(those estrogens made in placenta)

26. progesterone • made &secreted by corpus luteum • acts with estrogen to prepare uterine lining for implantation • quiets uterine muscle during early pregnancy • helps prepare breasts for lactation

27. placenta • produces hCG (human Chorionic Gonadotropin) • stimulates corpus luteum of ovary to continue producing estrogens and progesterone so lining of uterus does not slough off (like in menstruation) • turns pregnancy tests + • by 3rd mo pregnancy placenta produces estrogen & progesterone (ovaries become inactive rest of pregnancy) • also produces hPL (human placental lactogen) works w/E & P in preparing breasts for lactation

29. Pituitary disorders • Giantism: • hypersecretionhCG during chidhood • abnlincrese in length of long bones • hypersecretionhCG in adulthood  acromegaly (epiphyseal plates sealed) see thickening of bones of hands, face & thickening of skin on brow • Diabetes Insipidus: • defects in ADH • excrete large volumes of urine  dehydration & thirst (bed-wetting in children) • can die w/in 2 days from the dehydration Anterior Pituitary Posterior Pituitary

31. Thyroid gland disorders • Hypothyroidism: • Cretinism: congenital hypothyroidism • severe mental retardation if not tx’d • most states require testing new borns • Myxedema:adults • hallmark:edema of facial tissues, slow HR, low body temp, sensitivity to cold, dry skin & hair, muscle weakness

32. Cretinism & myxedema

33. Thyroid gland disorders • Graves Disease • most common form of hypothyroidism • 7 – 10 x more common in females • autoimmune disorder: autoantibodies that mimic TSH  causes thyroid to grow & make thyroid hormones • signs: enlarged thyroid, exophthalmos • tx: surgical excision of all or part of thyroid or use of antithyroid drugs to block synthesis of hormones

34. Graves disease

35. goiter • enlarged thyroid • could be associated with hypo- or hyperthyroidism, or euthyroidism (normal level of hormones) seen when intake of iodine too low

36. Adrenal Gland disorders • Cushing’s Syndrome: • hypersecretion of cortisol • caused by tumors that secrete • cortisol (in adrenal cortex) • ACTH  stimulates more cortisol production in adrenal cortex • muscle wasting  spindly arms & legs, “moon” face, “buffalo hump” red face • ~80% have hypertension

37. Cushing’s Syndrome

38. Adrenal gland disorders • Addison’s Disease: • hyposecretion of glucocorticoids & aldosterone • most are autoimmune: antibodies cause adrenal cortex destruction or block binding of ACTH to its receptors • TB can destroy adrenal cortex • symptoms: (after 90% of cortex destroyed) mental lethargy, anorexia, N/V, wt loss, hypotension, hypoglycemia, muscular weakness

40. Pancreatic islet disorders • Diabetes mellitus: (honey-sweetened) • inabillity to use or produce insulin • 4th leading cause death in USA • blood glucose levels high  glucosuria • 3 polys: polyuria, polydipsia, polyphagi

41. Diabetes Mellitus • Type 1: autoimmune abys destroy beta cells • mostly develops <20 yrs old • most common in northern European heritage • cells starved for glucose so switch to breaking down fatty acids  ketone production  ketoacidosis  untx’d  death • transport of lipids from adipocytes  plaque formation in walls of arteries = atherosclerosis • excess glucose attaches to proteins in lens  catarracts • small vessel disease: blindness, kidney failure, amputation of toes  legs, impotence

42. Diabetes Mellitus Treatment • self-monitoring of blood glucose levels  injections of insulin • Diet: • 45 – 50% carbohydrates • <30% fats Exercise

43. Type 2 Diabetes • non-insulin-dependent diabetes (NIDDM) • more common (90% of all cases) • typically occurs in obese people > 35 yrs old • #s children diagnosed increasing • many control it with diet, exercise, wt loss • oral hypoglycemic drugs • stimulates secretion of insulin from beta cells