Introduction to the Endocrine System: Maintaining Homeostasis and Hormonal Control

1. Chapter 12 The Endocrine System

2. Introduction • Maintains internal environment (homeostasis) • Hypothalamus: sends chemical signals to pituitary • Endocrine glands • Ductless • Secrete hormones directly into bloodstream

3. Introduction (cont’d.)

4. The Functions of Hormones

5. The Functions of Hormones • Control cellular respiration, growth and reproduction • Control body fluids and electrolyte balance • Control secretion of other hormones • Control behavior patterns • Regulate reproductive cycles, growth and development

6. The Functions of Hormones (cont’d.) • Chemical control functions as negative feedback loop • Thermostat turns furnace on when temperature falls below set point • Hormones function similarly

7. The Classification of Hormones

8. The Classification of Hormones • Modified amino acids • Epinephrine, oxytocin • Proteins • Insulin, growth hormones • Steroid • Cortisol, estrogen

9. The Hypothalamus of the Brain

10. The Hypothalamus of the Brain • Controls secretions of the pituitary gland • Nerve cells produce chemical signals • Releasing hormones • Releasing inhibitory hormones • Controlled by negative feedback from endocrine system

11. The Major Endocrine Glands and Their Hormones

12. The Anterior Pituitary Gland, Its Hormones, and Some Disorders • Growth hormone (GH): cell metabolism and growth • Decreased production • Dwarfism: childhood • Increased production • Gigantism: childhood • Acromegaly: post puberty

13. The Anterior Pituitary Gland, Its Hormones, and Some Disorders (cont’d.) • GH: cell metabolism and growth • Controlled by two releasing hormones from hypothalamus • Thyroid-stimulating hormone (TSH): stimulates thyroid • Adrenocorticotropic hormone (ACTH): stimulates adrenal cortex

14. The Anterior Pituitary Gland, Its Hormones, and Some Disorders (cont’d.) • Melanocyte-stimulating hormone (MSH): stimulates melanocytes • Follicle-stimulating hormone (FSH) • Females • Stimulates ovarian follicle development • Males • Stimulates sperm cell production

15. The Anterior Pituitary Gland, Its Hormones, and Some Disorders (cont’d.) • Luteinizing hormone (LH) • Females • Stimulates ovulation and progesterone production • Males • Testosterone production

16. The Anterior Pituitary Gland, Its Hormones, and Some Disorders (cont’d.) • Lactogenic hormone (prolactin): stimulates milk production in females • May cause decrease in male sex hormones

17. The Posterior Pituitary Gland and Its Hormones • Antidiuretic hormone (ADH) • Increased water reabsorption in kidney tubules • Deficiency results in diabetes insipidus • Regulated through osmoreceptors • Dehydration causes water conservation

18. The Posterior Pituitary Gland and Its Hormones (cont’d.) • Oxytocin • Contraction of uterine smooth muscles • Constriction of mammary gland cells (lactation) • Given after childbirth to constrict blood vessels to minimize risk of hemorrhage

19. The Thyroid Gland, Its Hormones, and Some Disorders • Located below larynx on either side of trachea • Requires iodine

20. The Thyroid Gland, Its Hormones, and Some Disorders (cont’d.) • Hormones • Thyroxine (T4): metabolism • Triiodothyronine (T3): metabolism • Calcitonin: regulation of calcium and phosphate concentration

21. The Thyroid Gland, Its Hormones, and Some Disorders (cont’d.) • Hypothyroidism • Cretinism • Lowered metabolic rate • Myxedema

22. The Thyroid Gland, Its Hormones, and Some Disorders (cont’d.) • Hyperthyroidism • Elevated metabolism • Graves’ disease • Exophthalmia

23. The Parathyroid Glands, Their Hormones, and Some Disorders • Located within the posterior thyroid gland • Chief cells secrete parathormone (PTH) • PTH stimulates bone cell release of calcium and phosphate

24. The Parathyroid Glands, Their Hormones, and Some Disorders (cont’d.) • Hyperparathyroidism • Breakdown of bone matrix • Hypoparathyroidism • Low calcium level in blood

25. The Parathyroid Glands, Their Hormones, and Some Disorders (cont’d.) • Position of the parathyroid glands

26. The Adrenal Glands, Their Hormones, and Some Disorders • Located on top of each kidney • Adrenal medulla: epinephrine and norepinephrine • Adrenal cortex: aldosterone, cortisol, androgens

27. The Adrenal Glands, Their Hormones, and Some Disorders (cont’d.) • Disorders • Addison’s disease: lack of adrenal cortex hormones • Cushing’s Syndrome: too much adrenal cortex hormones

28. The Pancreas, Its Hormones, and Some Disorders • Islets of Langerhans • Beta cells: insulin production • Alpha cells: glucagon production • Blood glucose levels regulated by negative feedback

29. The Pancreas, Its Hormones, and Some Disorders (cont’d.) • Disorders • Low blood glucose: acidosis • High blood glucose: excess kidney production, dehydration • Diabetes mellitus: insufficient insulin production

30. The Testes and the Ovaries • Testes: testosterone • Development of male reproduction structures • Development of male sex characteristics • Ovaries: estrogen and progesterone • Development of female reproductive organs • Development of female sex characteristics • Control menstrual cycle

31. The Thymus Gland and Its Hormone • Located behind the sternum • Secretes thymosin • Important for T-cell production • Thymus shrinks as we age

32. The Pineal Gland and Its Hormone • Located in the brain near the thalamus • Melatonin • Inhibits reproductive functions • Regulates body rhythms • Serotonin: neurotransmitter and vasoconstrictor • Stimulates smooth muscle contractions

33. Animation – Endocrine System Click Here to Play Endocrine System Animation

34. Summary • Discussed the functions of hormones • Classified hormones into their major chemical categories • Described how the hypothalamus controls the endocrine system

35. Summary (cont’d.) • Named the major endocrine glands and described the effects of their hormones on the body