Endocrine System


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Endocrine System

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Endocrine System

  2. 2. Basic Glands in the Body: 1. Exocrine gland  Its secretions are carried to a specific location by tube or duct. 2. Endocrine gland  Its secretions diffuse with the blood and are transported via the circulatory system to the target cells.  They are fondly called “ductless glands”.
  3. 3. HORMONES  Chemical messengers secreted by the endocrine glands and tissues which are carried throughout the body by the blood that have stimulatory, inhibitory, and regulatory effects to the target cells.
  4. 4. Effects of hormone  stimulation or inhibition of growth  Mood swings  induction or suppression of apoptosis (programmed cell death)  activation or inhibition of the immune system  regulation of metabolism  preparation of the body for fighting, sex, fleeing, mating, and other activity  preparation of the body for a new phase of life, such as puberty, parenting, and menopause  control of the reproductive cycle  hunger cravings
  5. 5. TYPES OF HORMONES 1. Steroid hormones  Lipids or derivatives of cholesterol  Have complex of four carbon rings but with different side chains.  E.g. Sex hormones (estrogen & progesterone) 2. Peptide hormone  Peptides, proteins, glycoproteins, or modified amino acids.
  6. 6. MECHANISMS OF HORMONAL ACTION  1st messenger model  accomplished by the steroid hormone.  2nd messenger model  accomplished by the peptide hormone.
  7. 7. 1st messenger model  Steroid hormone after crossing the cell membrane, combines with a receptor protein in the cytoplasm to form a hormone-receptor complex.  This complex moves into the nucleus and interacts with the nuclear DNA which promotes mRNA synthesis that moves into the cytoplasm and serves as template for the synthesis of proteins, usually enzymes.  The synthesized enzymes, in turn, enable reactions that produce the effect that is characteristic of a particular hormone.
  8. 8. 2nd messenger model  This model of hormonal action involves two messengers.  The 1st messenger is the hormone that binds to a receptor protein the cell membrane to form a hormone- receptor complex which in turn activates a certain enzyme called adenylate cyclase that stimulates the conversion of ATP into cyclic AMP (cAMP) or cyclic adenosine monophosphate.  This cAMP serves as the 2nd messenger that sets in motion an enzyme cascade, that is, each enzyme in turn activate another enzyme.  This enzyme activation carries the necessary characteristic effects of the hormone to its target cells.
  9. 9. Gland/Source HORMONES FUNCTIONS EFFECTS OF DEFICIENCY OR EXCESS PITUITARY GLAND OR HYPOPHYSIS A. Anterior Pituitary TSH or thyroid stimulating hormone Regulates production of the thyroid gland ACTH or adrenocorticotropic hormone Stimulates adrenal cortex to secrete its hormones FSH or follicle- stimulating hormone Promotes dev’t. of ovarian follicles and mature sperm LH or luteinizing hormone Evokes ovulation, formation of corpus luteum, and production and release of estrogens and progesterone.
  10. 10. Gland/Source HORMONES FUNCTIONS EFFECTS OF DEFICIENCY/ EXCESS Prolactin or Lactogenic hormone Stimulates milk secretion by mammary glands. Growth hormone or somatotropin Promotes cell metabolism Dwarfism (deficiency) Gigantism (excess in early youths) Acromegaly (excess later in life) MSH or melanophore stimulating hormone Controls adjustable skin pigment cells ( as in frogs)
  11. 11. Gland/Source HORMONES FUNCTIONS EFFECTS OF DEFICIENCY/ EXCESS A. Posterior Pituitary Vasopressin (antidiuretic hormone or ADH) Increases absorption of water by the kidney tubules; causes constriction of the smooth muscles of the arterioles. Oxytocin Causes contraction of the smooth muscles in the uterus; also causes ejection of milk from the mammary gland.
  12. 12. Gland/Source HORMONES FUNCTIONS EFFECTS OF DEFICIENCY OR EXCESS THYROID Thyroxine Triiodothyronine Calcitonin These hormones regulate the general body metabolism, growth and sexual dev’t. Regulates blood calcium (antagonizes bone resorption by osteoclasts. Deficiency: Simple Goiter Cretinism Myxedema Excess: Exophthalmic goiter. PARATHYROID Parathormone Controls Ca and phosphate concentration in blood plasma and their metabolism Muscular twitchings and spasmodic contractions of increasing violence , leading to severe convulsions.
  13. 13. Gland/Source HORMONES FUNCTIONS EFFECTS OF DEFICIENCY OR EXCESS ADRENAL CORTEX Mineralococorticoids (e.g.aldosterone) Glucocorticoids (cortisol and cortisone) Androgen Affects the metabolism of water and electrolytes and the serum concentrations of Na and K. Influencing the metabolism of carbohydrates and proteins Affects sexual dev’t. Addison’s disease In excess caused masculinizing effects for women ADRENAL MEDULLA Adrenaline Noradrenaline “ fight or flight” reaction Ex. raises BP, heart rate, blood sugar level Inability to cope with stress
  14. 14. Gland/Source HORMONES FUNCTIONS EFFECTS OF DEFICIENCY OR EXCESS PANCREAS (Islets of langerhans) Insulin glucagon Glucose to glycogen Conversion Glycogen to glucose conversion Diabetes mellitus DUODENUM Secretin Pancreozymin Stimulates pancreatic Juice secretion STOMACH Gastrin Stimulates gastric juice secretion
  15. 15. Gland/Source HORMONES FUNCTIONS EFFECTS OF DEFICIENCY OR EXCESS TESTIS Testosterone other Androgens Anabolic: growth of muscle mass and strength, increased bone density, growth and strength, Virilizing: maturation of sex organs, formation of scrotum, deepening of voice, growth of beard and axillary hair. Atrophy of reproductive system OVARY OR FOLLICLE Estradiol other estrogen Stimulates sex characteristics, sex urge Decline of secondary sex cha racteristics (deficiency) OVARY OR CORPUS LUTEUM Progesterone Promotes thickenings of the endometrium; induce mammary gland enlargement; inhibits further ovulation by antagonizing FSH secretion Abortion during pregnancy (deficiency)
  16. 16. Gland/Source HORMONES FUNCTIONS EFFECTS OF DEFICIENCY OR EXCESS PLACENTA (pregnancy) progesterone Maintains thickenings of the endometrium. PINEAL GLAND melatonin Concentrates the pigment of melanophores of fishes and amphibians; inhibits gonadal dev’t. and is involved in the regulation of circadian rhythms