Anatomy Summary: Hormones

1. Anatomy Summary: Hormones Figure 7-2 (1 of 2)

2. Anatomy Summary: Hormones Figure 7-2 (2 of 2)

3. Pituitary gland (Hypophysis) • Pituitary gland – two-lobed organ that secretes nine major hormones • Neurohypophysis – posterior lobe (neural tissue) and the infundibulum • Receives, stores, and releases hormones from the hypothalamus • Adenohypophysis – anterior lobe, made up of glandular tissue • Synthesizes and secretes a number of hormones

5. Neurohypophysis hormones Hormones that are produced in the hypothalamus and stored in the neurohypophysis

6. HYPOTHALAMUS 1 Hormone is made and packaged in cell body of neuron. 2 Vesicles are transported down the cell. 3 Vesicles containing hormone are stored in posterior pituitary. POSTERIOR PITUITARY Vein 4 Hormones are released into blood. Figure 7-12, steps 1–4

7. Hypophyseal portal system • Portal system - a system of blood vessels that begins and ends in capillaries. The blood, after passing through one capillary bed, is passing through a second capillary network. • All blood entering the portal system will reach the target cells before returning to the general circulation Question – why is such a system important in the communication between the hypothalamus and the hypophysis?

8. Pituitary-Hypothalamic Relationships: anterior Lobe • The hypophyseal portal system, consisting of: • The primary capillary plexus in the infundibulum • The hypophyseal portal veins • The secondary capillary plexus

9. The anterior lobe • There is no direct neural contact with the hypothalamus • Hormone production is regulated by the hypothalamus • Regulatory factors from the hypothalamus arrive directly to the adenohypophysis through the hypophyseal portal system • Releasing hormones stimulate the synthesis and release of hormones • Inhibiting hormones shut off the synthesis and release of hormones • The hormones of the anterior pituitary (7) are called tropic/trophic hormones because they “turn on” other glands or organs

10. Tropic Hormones of the Anterior Pituitary

11. The Pituitary Gland: Anterior HYPOTHALAMIC HORMONES Neurons in hypothalamus secreting trophic hormones Dopamine* TRH CRH GHRH* GnRH PRFs Somatostatin Portal system Anterior pituitary ANTERIOR PITUITARY HORMONES TSH ACTH Prolactin GH FSH LH Endocrine cells (Gonadotropins) To target tissues ENDOCRINE TARGETS AND THE HORMONES THEY SECRETE Endocrine cells of the gonads Thyroid gland Adrenal cortex Liver Thyroid hormones Estrogens, progesterone Cortisol IGFs Androgens NONENDOCRINE TARGETS Germ cells of the gonads Many tissues Breast Figure 7-13

12. Anterior pituitary hormones

13. Anterior pituitary hormones

14. Anterior pituitary hormones

15. Anterior pituitary hormones

16. Thyroid Gland The thyroid gland on the anterior side of the neck. The thyroid gland has a right lobe and a left lobe connected by a narrow isthmus http://webanatomy.net/histology/endocrine_histology.htm

17. Thyroid Hormone • Thyroid hormone – major metabolic hormone • Consists of two related iodine-containing compounds • T4 – thyroxine; has two tyrosine molecules plus four bound iodine atoms • T3 – triiodothyronine; has two tyrosines with three bound iodine atoms

18. Functions of Thyroid Hormones Elevates rates of oxygen consumption and energy consumption; in children, may cause a rise in body temperature Increases heart rate and force of contraction; generally results in a rise in blood pressure Increases sensitivity to sympathetic stimulation Stimulates red blood cell formation and thus enhances oxygen delivery Activate genes that code for enzymes that are involved in glycolysis (Glucose oxidation) increase rate of ATP production In the nucleus – activate genes that control the synthesis of enzymes that involve with energy production and utilization (for example increase of production of sodium-potassim ATPase that uses ATP)

19. Thyroid Hormone Control Pathway Tonic release Hypothalamus TRH Anteriorpituitary TSH Negative feedback Thyroidgland T4, T3 T4 T3 KEY Stimulus Integrating center Efferent pathway Systemicmetaboliceffects Effector Systemic response Figure 23-11

20. Protein hormones that control calcium • Parathyroid gland – PTH • PTH—most important hormone in Ca2+homeostasis • Thyroid gland – calcitonin • Liver and Kidney - Calcitriol – also known as vitamin D3

21. Calcitonin • Calcitonin targets the skeleton, where it: • Inhibits osteoclast activity (and thus bone resorption) and release of calcium from the bone matrix • Stimulates calcium uptake and incorporation into the bone matrix • Regulated by a humoral (calcium ion concentration in the blood) negative feedback mechanism

22. Effects of Parathyroid Hormone • PTH release increases Ca2+ in the blood: • Stimulates osteoclasts to digest bone matrix • Enhances the reabsorption of Ca2+ and the secretion of phosphate by the kidneys • Increases absorption of Ca2+ by intestinal mucosal • Rising Ca2+ in the blood inhibits PTH release • The antagonist is the Calcitonin secreted by the thyroid gland

23. Simple Endocrine Reflex: Parathyroid Hormone Low plasma [Ca2+] Negative feedback Parathyroid cell Parathyroid hormone Bone and kidney Kidney reabsorption of calcium Production of calcitriol leads to intestinal absorption of Ca2+ Bone resorption Plasma [Ca2+] Figure 7-10

24. Pancreas structure Exocrine pancreas (99% of volume) Cells (pancreatic acini) forming glands and ducts that secrete pancreatic fluid and enzymes with digestive function Endocrine pancreas (1%) Small groups of cells scattered in clusters (pancreatic islets) that secrete hormones

25. Adrenal (Suprarenal) Glands • Structurally and functionally, they are two glands in one • Adrenal medulla – neural tissue; part of the sympathetic nervous system • Adrenal cortex - three layers of glandular tissue that synthesize and secrete corticosteroids

26. Adrenal Cortex • Synthesizes and releases steroid hormones called corticosteroids • Different corticosteroids are produced in each of the three layers • Zonaglomerulosa – glomerulus- little ball. Secretes mineralocorticoids – main one aldosterone • Zonafasciculata– glucocorticoids (chiefly cortisol) • Zonareticularis – gonadocorticoids (chiefly androgens)

27. Zonaglomerulosa – Mineralocorticoids • Aldosterone secretion is stimulated by: • Rising blood levels of K+ • Low blood Na+ • Decreasing blood volume or pressure

28. Aldosterone and urine concentration • Aldosterone is a steroid secreted by the adrenal cortex • It is secreted when blood sodium falls or if blood potassium rises or when blood pressure decreased • Aldosterone increases reabsorption of Na+in the kidneys in exchange for secretion of K+ ions – water follow • Net effect is that the body retains NaCl and water and urine volume reduced • The retention of salt and water help to maintain blood pressure and volume

29. Zonafasciculata - Glucocorticoids (Cortisol/hydrocortisone) • Main hormones secreted are the Cortisol/hydrocortisone and small amounts of corticosterone • It protects against hypoglycemia by stimulating catabolism of energy stores. • While adrenaline is responsible for rapid metabolic responses the glucocorticoids are responsible for long-term stress: • Glucocorticoids accelerate the rates of glucose synthesis and glycogen formation – especially in the liver • Promotes the utilization of fatty acids as source of energy - glucose-sparing effect • Clucocorticoids also have anti-inflammatory effect – inhibit the activities of WBC (use?)