Concepts endocrines system.ppt
- 2. Messenger Molecules • Cells must communicate with one another to coordinate cell processes within tissues and to maintain homeostasis. • Cell-to-cell communication is carried out via messenger molecules.
- 3. Three types of chemical signals are used for cell- to-cell communication.
- 4. Four methods of cell-to-cell communication are found in the human body, ranging from direct to remote communication.
- 5. Endocrine hormones • Produced by endocrine (“ductless”) glands and secreted into the bloodstream. • Endocrine hormones may affect a wide array of target cells to produce multiple effects. • Two types: peptides (small proteins) and steroids (lipids).
- 7. Peptide Hormones • Peptide hormones do not enter the cell directly. These hormones bind to receptor proteins in the cell membrane. • When the hormone binds with the receptor protein, a secondary messenger molecule initiates the cell response. • Because peptide hormones are water soluble, they often produce fast responses.
- 8. (cytoplasm) (nucleus) peptide or amino acid-derived hormone (first messenger) (extracellular fluid) cyclic AMP- synthesizing enzyme cyclic AMP ATP inactive enzyme (second messenger) active enzyme reactant product plasma membrane nuclear envelope receptor The hormone binds to a receptor on the plasma membrane of a target cell 1 The activated enzymes catalyze specific reactions 4 The second messenger activates other enzymes 3 Hormone–receptor binding activates an enzyme that catalyzes the synthesis of a second messenger, such as cyclic AMP 2
- 9. Steroid Hormones • Steroid hormones enter through the cell membrane and bind to receptors inside of the target cell. • These hormones may directly stimulate transcription of genes to make certain proteins. • Because steroids work by triggering gene activity, the response is slower than peptide hormones.
- 10. gene plasma membrane ribosome hormone receptor steroid hormone mRNA (nucleus) RNA polymerase DNA (cytoplasm) new protein (extracellular fluid) A steroid hormone diffuses through the plasma membrane The hormone binds to a receptor in the nucleus or to a receptor in the cytoplasm that carries it into the nucleus The hormone–receptor complex binds to DNA and causes RNA polymerase to bind to a nearby promoter site for a specific gene RNA polymerase catalyzes the transcription of DNA into messenger RNA (mRNA) The mRNA leaves the nucleus, then attaches to a ribosome and directs the synthesis of a specific protein product 1 2 3 4 5 nuclear envelope
- 11. Role of the Hypothalamus • The thalamus receives sensory information, relays some to the hypothalamus. • Hypothalamus monitors the body for temperature, pH, other conditions. • Hypothalamus signals pituitary gland if conditions need to be corrected.
- 12. Role of the Pituitary • The pituitary signals other glands to produce their hormones when needed. • The anterior lobe of the pituitary receives signals from the hypothalamus, and responds by sending out the appropriate hormone to other endocrine glands. • The posterior pituitary receives oxytocin or antidiuretic hormone (ADH) from the hypothalamus, relays them to the body as necessary.
- 13. hypothalamus pituitary (anterior lobe) capillary bed endocrine cell blood flow blood flow capillary bed pituitary (posterior lobe) Oxytocin and ADH (blue triangles) are secreted into the blood via capillaries in the posterior pituitary Endocrine cells of the anterior pituitary secrete hormones (red squares) in response to releasing hormones; the pituitary hormones enter the bloodstream Neurosecretory cells of the hypothalamus produce oxytocin and ADH Releasing or inhibiting hormones (green circles) are secreted into capillaries feeding the anterior lobe of the pituitary Neurosecretory cells of the hypothalamus produce releasing and inhibiting hormones 1 2 1 2 3
- 14. Pituitary Hormones Pituitary Hormone Functions Follicle-stimulating hormone Stimulates egg maturation in the ovary and release of sex hormones. Lutenizing hormone Stimulates maturation of egg and of the corpus luteum surrounding the egg, which affects female sex hormones and the menstrual cycle. Thyroid-stimulating hormone Stimulates the thyroid to release thyroxine. Adrenocorticotropic hormone Causes the adrenal gland to release cortisol. Melanocyte-stimulating hormone Stimulates synthesis of skin pigments. Growth hormone Stimulates growth during infancy and puberty. Antidiuretic hormone Signals the kidney to conserve more water. Oxytocin Affects childbirth, lactation, and some behaviors.
- 15. Endocrine Hormones Gland Hormones Functions Thyroid Thyroxine Regulates metabolism Calcitonin Inhibits release of calcium from the bones Parathyroids Parathyroid hormone Stimulates the release of calcium from the bones. Islet cells (in the pancreas) Insulin Decreases blood sugar by promoting uptake of glucose by cells. Glucagon Increases blood sugar by stimulating breakdown of glycogen in the liver. Testes Testosterone Regulates sperm cell production and secondary sex characteristics. Ovaries Estrogen Stimulates egg maturation, controls secondary sex characteristics. Progesterone Prepares the uterus to receive a fertilized egg. Adrenal cortex Epinephrine Stimulates “fight or flight” response. Adrenal medulla Glucocorticoids Part of stress response, increase blood glucose levels and decrease immune response. Aldosterone Regulates sodium content in the blood. Testosterone (in both sexes) Adult body form (greater muscle mass), libido. Pineal gland Melatonin Sleep cycles, reproductive cycles in many mammals.
- 16. Homeostasis and Hormones • Examples: • Thyroid and temperature control • Thyroid, Parathyroid, and calcium • Pancreas and glucose control
- 18. Blood Calcium
- 20. Other hormone roles • Controlling sleep cycles (melatonin) • Controlling reproductive cycles (melatonin, sex hormones) • Growth (growth hormone) • Responding to stress or emergencies (epinephrine and other hormones)
- 21. Hormones Everywhere! • Many other organs besides the endocrine glands produce hormones. • Kidneys produce several hormones that regulate blood pressure, which is essential for kidney function. • The digestive system produces several hormones that regulate appetite.
- 22. Low body fat stimulates leptin production, which stimulates appetite. The mouse is obese because its low leptin levels give it an enormous appetite. Leptin injections return the mouse’s weight to normal. Humans sometimes have a leptin issue, too, but the problem is a bad leptin receptor on body cells. Alas, leptin injections won’t cure that. The obese mouse on the left does not produce enough leptin, a hormone produced by fat cells.
- 23. Thyroid Gland Thyroid Gland Located along the midline of the neck Secretes two nonsteroid hormones Triiodothyronine (T3) Thyroxine (T4) Calcitonin: calcium metabolism (osteoblast) Regulates metabolism increases protein synthesis promotes glycolysis, gluconeogenesis, glucose uptake
- 24. Thyroid Gland
- 25. Thyroid Gland
- 26. Parathyroid Glands • Embedded in posterior surface of the thyroid gland • Parathyroid hormone (PTH) • Produced by chief cells • In response to low concentrations of Ca2+
- 28. Suprarenal (Adrenal) Gland • Lie along superior border of each kidney • Subdivided into: • Superficial suprarenal cortex • Stores lipids, especially cholesterol and fatty acids • Inner suprarenal medulla • Secretory activities controlled by sympathetic division of ANS
- 29. Suprarenal (Adrenal) Gland Adrenal Medulla Contains two types of secretory cells Epinephrine (70-75% of mass) Increase H.R. and B.P. Increase respiration Increase metabolic rate Increase glycogenolysis Bronchodilation Norepinephrine (20-25% of mass) Vasoconstriction
- 30. Suprarenal (Adrenal) Gland • Adrenal Cortex • Mineralocorticoids (Zona Glomerulosa) • Aldosterone: maintains electrolyte balance • Na+ reabsorption by kidneys & K+ urinary loss • Glucocorticoids (Zona Fasciculate) • Cortisol (Hydrocortisone): • Stimulates gluconeogenisis • Mobilization of free fatty acids • Anti-inflammatory agent • Androgens (Zona Recticularis) • Bone growth, muscle growth & blood formation
- 31. Pineal Gland • Lies in posterior portion of roof of third ventricle • Contains pinealocytes • Synthesize hormone melatonin • Inhibits reproductive functions • Protects against damage from free radicals • Setting circadian rhythms
- 32. Pancreas • Exocrine / Endocrine Gland • Endocrine Pancreas consists of “clusters” of cells called Islets of Langerhans • 4 types of cells of endocrine pancreas • Comprise only 1% of entire pancreas
- 33. Pancreas • Insulin • A peptide hormone released by beta cells • Affects target cells by: • Accelerate glucose uptake • Accelerate glucose utilization and enhances ATP formation • Stimulate glycogen formation • Stimulate amino acid absorption and protein synthesis • Stimulate triglyceride formation in adipose tissue
- 34. Pancreas • Glucagon • Released by alpha cells • Mobilizes energy reserves • Affects target cells: • Stimulates breakdown of glycogen in skeletal muscle and liver tissue • Stimulates breakdown of triglycerides in adipose tissue • Stimulates production of glucose in liver
- 36. Sex Organs (Testes & Ovaries) • Testes (Gonads) • Produce androgens in interstitial cells • Testosterone is the most important male hormone • Secrete inhibin in nurse (sustentacular) cells • Support differentiation and physical maturation of sperm • Ovaries (Gonads) • Produce estrogens • Principle estrogen is estradiol • After ovulation, follicle cells • Reorganize into corpus luteum • Release estrogens and progestins, especially progesterone
- 37. Thymus Produces thymosins (blend of thymic hormones) That help develop and maintain normal immune defenses
- 38. Endocrine Tissues of Other Organs • Kidneys: • Produce calcitriol and erythropoietin • Produces enzyme renin • Heart: • Produces natriuretic peptides (ANP & BNP) • When blood volume becomes excessive • Action opposes angiotensin II • Resulting in reduction of blood pressure & volume
- 40. Hormone Interactions • General Adaptation Syndrome (GAS) • Also called stress response • How body responds to stress-causing factors • Is divided into three phases: 1. Alarm phase 2. Resistance phase 3. Exhaustion phase
Editor's Notes
- #26: Thyroid-Stimulating Hormone (TSH) Absence causes thyroid follicles to become inactive Neither synthesis nor secretion occurs Binds to membrane receptors Activates key enzymes in thyroid hormone production Thyroid Hormones Enter target cells by transport system Affect most cells in body Bind to receptors in Cytoplasm Surfaces of mitochondria Nucleus In children, essential to normal development of Skeletal, muscular, and nervous systems Calorigenic Effect Cell consumes more energy resulting in increased heat generation Is responsible for strong, immediate, and short-lived increase in rate of cellular metabolism T3/T4 Deficiency: Myxedema / Cretinism – Low metabolic rate / low body temperature / impaired physical & mental development T3/T4 Overproduction: Hyperthyroidism / Graves Disease – High metabolic rate / temperature
- #28: Four Effects of PTH It stimulates osteoclasts Accelerates mineral turnover and releases Ca2+ from bone It inhibits osteoblasts Reduces rate of calcium deposition in bone It enhances reabsorption of Ca2+ at kidneys, reducing urinary loss It stimulates formation and secretion of calcitriol at kidneys Effects complement or enhance PTH Enhances Ca2+, PO43- absorption by digestive tract PTH Deficiency: Hypoparathyroidism – Muscular weakness, neurological problems, formation of dense bones, tetany due to low blood Ca PTH Overproduction: Hyperparathyroidism – Neurological, mental, muscular problems due to high blood Ca, weak brittle / bones
- #30: Interesting that both hormones when released by Adrenal gland, but neurotransmitters when released at synapses Catacholeamine Deficiency: None known Catacholeamine Overproduction: Pheochromocytoma – High metabolic rate, elevated temperature, high HR and blood glucose levels
- #31: Aldosterone Deficiency: Hypoaldosteronism – Polyuria, low blood volume, high serum K, low serum Na Aldosterone Overproduction: Aldosteronism – Increased body weight due to Na & water retention, low serum K Glucocorticoids Deficiency: Addison’s Disease – Inability to tolerate stress, mobilize energy reserves or maintain normal blood glucose levels Glucocorticoids Overproduction: Cushing Disease – Excessive break down of tissue proteins and lipid reserves, impaired glucose metabolism
- #34: Insulin Deficiency: Diabetes Mellitus – High blood sugars, impaired glucose utilization, dependance on lipids of energy, glycosuria Insulin Overproduction: (Iatrogenic / Tumor) – Low blood sugars
- #37: Female: Estrogens Deficiency: Hypogonadism– Sterility, lack of secondary sex characteristics Estrogen Overproduction: Adrenogenital Syndrome – Masculinization Precocious puberty – Premature sexual maturation, related behavioral changes Male: Androgen Deficiency: Hypogonadism– Sterility, lack of secondary sex characteristics Androgen Overproduction: Adrenogenital Syndrome – Breast enlargement Precocious puberty – Premature sexual maturation, related behavioral changes
- #39: Kidneys sense lower GFR and lower blood oxygen saturations, release EPO
- #42: Fight or Flight Epinephrine is dominant hormone
- #43: Stresses that persist for hours / days / weeks – starvation, acute illness, etc Mobilization of remaining Lipid & Protein Reserves Conservation of Glucose for Neural Tissues Elevation & Stabilization of Blood Glucose concentration Conservation of Salts & Water and the Loss of K+ and H+