The Endocrine Sytem

1. The Endocrine Sytem • Second controlling system of the body • Nervous system is the fast-control system • Uses chemical messengers (hormones) that are released into the blood • Hormones control several major processes • Reproduction • Growth and development • Mobilization of body defenses • Maintenance of much of homeostasis • Regulation of metabolism

2. Pineal gland Hypothalamus Pituitary gland Thyroid gland Parathyroid glands Thymus Adrenal glands Pancreas Ovary (female) Testis (male) Figure 9.3

3. Chemical Make-up • Hormones are classified chemically as • Amino acid–based, which includes • Proteins • Peptides • Amines • Steroids—made from cholesterol • Prostaglandins—made from highly active lipids

4. Mechanisms of Hormone Action Hormones affect only certain tissues or organs (target cells or target organs) Target cells must have specific protein receptors Hormone-binding alters cellular activity

5. Nucleus Cytoplasm Steroidhormone Receptorprotein 1 2 3 Hormone-receptor complex 4 DNA mRNA 5 Newprotein Plasmamembraneof targetcell 6 (a) Steroid hormone action Figure 9.1a

6. Nonsteroidhormone (first messenger) Cytoplasm Enzyme ATP 3 1 2 Secondmessenger cAMP 4 Receptorprotein Effect on cellular function, such as glycogenbreakdown Plasma membraneof target cell (b) Nonsteroid hormone action Figure 9.1b

7. Control of Hormone Release Hormone levels in the blood are mostly maintained by negative feedback A stimulus or low hormone levels in the blood triggers the release of more hormone Hormone release stops once an appropriate level in the blood is reached

8. Hormonal Stimuli of Endocrine Glands Most common stimuli Endocrine glands are activated by other hormones

9. Hypothalamus Hypothalamus Hypothalamus Releasing hormones secreted into portal circulation Anterior pituitary Posterior pituitary Hypophyseal portal system Adrenocorticotropic hormone (ACTH) Growth hormone (GH) Thyrotropic hormone (TH) Adrenal cortex Bones and muscles Prolactin (PRL) Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) Mammary glands Thyroid Testes or ovaries Figure 9.4

10. Hypothalamic neurosecretory cells Optic chiasma Hypothalamus Axon terminals Arterial blood supply Posterior lobe Capillary bed Venous drainage Anterior lobe of the pituitary ADH Oxytocin Kidney tubules Mammary glands Uterine muscles Figure 9.6

11. Hypothalamus • Part of the brain that sits above the pituitary • They work together Anterior Pituitary • Growth hormone • Adrenocorticotropic hormone - ACTH • Thyroid stimulating hormone - TSH Posterior Pituitary • Antidiruetic hormone (ADH) – promotes re-absorption of water in kidney – increases BP • Oxytocin – uterine contractions

12. Adrenal Glands • Respond to ACTH by producing: • Glucocorticoids (cortisone) – produce glucose in blood through fatty acid breakdown, inhibit inflammation. • Mineralocorticoids (aldosterone) – promote uptake of sodium and chloride in kidneys, water follows, increase BP • Epinephrine - emergency hormone

13. Decreased Na+ or increased K+ in blood Stress Hypothalamus Decreased blood volume and/or blood pressure Corticotropin- releasing hormone Anterior pituitary Increased blood pressure or blood volume ACTH Kidney Renin Heart Indirect stimulating effect via angiotensin Atrial natriuretic peptide (ANP) Angiotensin II Direct stimulating effect Inhibitory effect Mineralocorticoid- producing part of adrenal cortex Enhanced secretion of aldosterone targets kidney tubules Increased blood volume and blood pressure Increased absorption of Na+ and water; increased K+ excretion Figure 9.12

14. Short term More prolonged Stress Hypothalamus Releasing hormones Nerve impulses Spinal cord Corticotropic cells of anterior pituitary ACTH Adrenal cortex Preganglionic sympathetic fibers Adrenal medulla Mineralocorticoids Glucocorticoids Long-term stress response Short-term stress response 1. Increased heart rate 2. Increased blood pressure 3. Liver converts glycogen to glucose and releases glucose to blood 4. Dilation of bronchioles 5. Changes in blood flow patterns, leading to increased alertness and decreased digestive and kidney activity 6. Increased metabolic rate 1. Proteins and fats converted to glucose or broken down for energy 2. Increased blood sugar 3. Suppression of immune system Catecholamines (epinephrine and norepinephrine) 1. Retention of sodium and water by kidneys 2. Increased blood volume and blood pressure Figure 9.13

15. Thyroid • Stimulated by Thyrotropin releasing hormone (TRH) from the hypothalamus which stimulates TSH from anterior pituitary. • Thyroxine (iodine) • Maintains metabolism • Hyperthyroidism – high metabolic rate, nervous, irritable • Hypothyroidism – low met. Rate, slow, sluggish, overweight • Calcitonin – takes up calcium from blood to bones

16. Disorders of the endocrine system • Goiter – iodine deficiency, thyroxin production declines • The hypothalamus secretes TRH, but has no effect • Results in enlargement of the thyroid • Grave’s disease – antibodies in the immune system mistakenly bind to TSH receptors on the thyroid gland stimulating more thyroxin production - hyperthyroidism

17. Parathyroids • Rest on the thyroid • Parathyroid hormone – releases calcium from bone to blood • Opposite of calcitonin • Bone remodeling

18. Calcitonin Calcitonin stimulates calcium salt deposit in bone. Thyroid gland releases calcitonin. Stimulus Rising blood Ca2+ levels IMBALANCE Calcium homeostasis of blood: 9–11 mg/100 ml BALANCE BALANCE Stimulus Falling blood Ca2+ levels IMBALANCE Thyroid gland Osteoclasts degrade bone matrix and release Ca2+ into blood. Parathyroid glands Parathyroid glands release parathyroid hormone (PTH). PTH Figure 9.10

19. Bone growth Bone remodeling Growing shaft is remodeled as: Bone grows in length because: Articular cartilage 1 Cartilage grows here. Epiphyseal plate 2 Cartilage is replaced by bone here. 1 Bone is resorbed here. 3 2 Cartilage grows here. Bone is added by appositional growth here. 4 Cartilage is replaced by bone here. 3 Bone is resorbed here. Figure 5.6

20. Pancreas • Islets of Langerhans – produce insulin and glucagon • Glucagon stimulates glycogen to break into glucose molecules and be released into the blood • Insulin decreases the glucose in the blood

21. Uptake of glucose from blood is enhanced in most body cells Insulin-secreting cells of the pancreas activated; release insulin into the blood Tissue cells Insulin Glycogen Glucose Pancreas Blood glucose falls to homeostatic set point; stimulus for insulin release diminishes Elevated blood sugar level Liver takes up glucose and stores as glycogen IMBALANCE Stimulus Blood glucose level (e.g., after eating four jelly doughnuts) BALANCE: Normal blood glucose level (about 90 mg/100 ml) Stimulus Blood glucose level (e.g., after skipping a meal) IMBALANCE Blood glucose rises to homeostatic set point; stimulus for glucagon release diminishes Low blood sugar level Glucagon-releasing cells of pancreas activated; release glucagon into blood Glucose Glycogen Liver breaks down glycogen stores and releases glucose to the blood Liver Glucagon Figure 9.15

22. thermoregulation • Ectotherm vs. endotherm • Cooling by evaporation • Warming by metabolism – shivering and metabolizing fat • Vasodilation and vasoconstriction of blood vessels Ex. In hot environments, animals increase blood flow to their ears to release heat and in cold do the opposite. • Countercurrent exchange – warm blood is traveling to extremities. • Hibernation, blubber, hair, basking,…

23. Reproductive Systems • Female • Ovaries – produce eggs (ova) and secrete estrogen and progesterone • Stimulated by FSH and LH • Male • FSH – stimulates sperm production • LH – stimulates interstitial cells to produce testosterone

24. Suspensory ligament of ovary Uterine (fallopian) tube Ovarian blood vessels Fundus of uterus Lumen (cavity) of uterus Ovary Infundibulum Broad ligament Uterine tube Fimbriae Ovarian ligament Round ligament of uterus Body of uterus Endometrium Wall of uterus Myometrium Perimetrium Ureter Cervical canal Uterine blood vessels Uterosacral ligament Vagina Cervix (b) Figure 16.8b

25. Menstrual CyclePhase 1 Follicular phase (10 days) • Anterior pituitary secretes FSH and LH • FSH – follicle stimulating hormone • LH – luteinizing hormone • Follicle grows – releases estrogen which causes uterine lining to thicken-endometrium • Estrogen also causes ant. Pit. To release LH • The luteal surge causes ovulation

26. Growing follicles Primary follicle Degenerating corpus luteum Blood vessels Antrum Corona radiata Mature vesicular (Graafian) follicle Germinal epithelium Corpus luteum Developing corpus luteum Ruptured follicle Ovulation Secondary oocyte Figure 16.7

27. Ovulation – release of the egg from the ovary ends the follicular phase. • Ova floats into fallopian tube (oviduct)

28. Phase 2 Luteal phase • Follicle has released the egg and changes into the corpus luteum • Corpus luteum continues to secrete estrogen and now begins to produce progesterone • Progesterone increases vessels and glands in uterus • After about 13-15 days, if fertilization and implantation have NOT occurred the corpus luteum shuts down

29. Phase 3 Menstruation • Uterus reabsorbs some of the tissue created in the endometrium • The rest sheds off and is passed out of the body

31. Male Reproductive system Ureter Urinary bladder Seminal vesicle Prostatic urethra Ampulla of ductus deferens Pubis Membranous urethra Ejaculatory duct Urogenital diaphragm Rectum Erectile tissue of the penis Prostate Bulbourethral gland Spongy urethra Shaft of the penis Ductus (vas) deferens Glans penis Epididymis Testis Prepuce (a) Scrotum External urethral orifice Figure 16.2a