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ENDOCRINE SYSTEM ENDOCRINE SYSTEM I

VIEWS: 3 PAGES: 5

									ENDOCRINE SYSTEM

I.     I.      INTRODUCTION
       A.     A.       the purpose of the endocrine system is to maintain homeostasis; like the nervous
              system it provides control to maintain body function despite changing internal/external
              conditions
       B.     B.       compared top the nervous system which responds in a rapid manner but whose effects
              are short lived, the endocrine sys. response is slow but lasts longer and is widespread
       C.     C.       control is exerted by the secretion of hormones into the blood stream that target certain
              processes such as metabolism, reproduction, altering the internal and external chemical
              balances of cells and fluids, growth and development, and response to stress

II.    II.     COMPOSITION OF THE ENDOCRINE SYSTEM
       A.     A.    Endocrine vs. exocrine glands
              1.   1.        exocrine glands secrete chemicals into a duct which carries the chem. to the
                   target tissue or organ. example the gall bladder, sweat glands, etc.
              2.   2.        endocrine glands secrete chemicals (hormones) into extracellular space which
                   then diffuse into the bloodstream--ductless glands
       B.     B.    Primary endocrine glands
              1.   1.        pituitary gland, thyroid gland, parathyroid glds., adrenal glds., pancreas, gonads

III.   III.    HORMONES
       A.     A.        Definition: chemicals produced by endocrine glands that provide control of body
              activities to maintain homeostasis
       B.     B.        Target cell: cell that is effected by a hormone; all cells are targets of one or more
              hormones; hormones only act on their target cells because of receptors on the surface of the
              cell
       C.     C.        Hormonal action: water soluble vs. lipid soluble
              1.       1.       water soluble--made of amino acids and their derivatives and proteins; cannot
                       diffuse through plasma membrane
              2.       2.       binds to receptor on cell surface (adenylate cyclase) º converts ATP into
                       cAMP º cAMP diffuses throughout cells initiating reactions that lead to activation of
                       protein kinasesº activates other proteins in cell which act on molecules to change cell
                       a.      a.        changes may include stimulating or inhibiting metabolic pathways,
                               synthesis of proteins, altering membranes, secretion of cellular products
                               including hormones
              3.       3.       lipid soluble--steroid hormones that diffuse easily through plasma mem.
              4.       4.       binds to receptors in the cytoplasmº steroid/receptor move into nucleus and
                       bind to DNAº turns on the synthesis of specific genes to make proteins
                       (transcription/translation)
                       a.      a.        new proteins do specific jobs such as stimulating or inhibiting
                               metabolic pathways, altering rates of reactions or become structural components
                               of the cell
              5.       5.       prostaglandins--steroids that are secreted by different parts of the body, act on
                       cells close to them (local hormones)
                       a.      a.        act by modifying effects of other hormones by inhibiting or stimulating
                               formation of cAMP, not true hormones
                       b.      b.       increase or decrease smooth muscle contraction, secretion of HCL in
                               stomach, contraction of uterus, cause inflammation, regulate metabolism, induce
                               sleep, antineoplastic
      D.    D.      Hormonal control
            1.    1.       feedback control--hormones are very potent chemicals, uncontrolled release
                  would not be good ;
            2.    2.       negative feedback system--provides response on opposite direction of stimulus,
                  the feedback is given by the hormone or its products which inhibit further hormone
                  secretion; most feedback systems in the body are this type
                  a.      a.       example: parathyroid gland and blood calcium levels
            3.    3.       positive feedback--provides response in same direction as stimulus, chemical
                  feedback causes endocrine gland to secrete more hormone; move body further from
                  homeostasis
                  a.      a.       example: oxytocin produced by post. pituitary and uterine contractions
            4.    4.       nervous control--only controls a few glands which secrete their hormones when
                  they receive nerve impulses
IV.   IV.    THE ENDOCRINE GLANDS
      A.    A.      Pituitary gland
            1.    1.       located at base of brain, the size of pea weighing .5g, attached to hypothalamus
                  by infundibulum and lies within bony cavity called sella turcica
            2.    2.       anterior lobe--composed of glandular epithelium enclosed by connective tissue,
                  release of 7 hormones controlled by releasing factors (R) from the hypothalamus
                  a.      a.       Growth hormone (GH) --stimulates body cells to grow and divide,
                          increases bone deposition, causes cells to increase uptake of A.A.s and increase
                          catabolism, helps maintain blood sugar by increasing conversion of glycogen to
                          glucose
                  b.      b.       Melanocyte-stimulating hormone (MSH)--increases melanin
                          production in skin
                  c.      c.       Prolactin (PRL) --stimulates and maintains milk secretion by
                          mammary glands, secretion plus ejection of milk is called lactation, levels of
                          PRL are also influenced by other hormonal changes..
                  d.      d.       Thyroid-stimulating hormone (TSH)--stimulates thyroid gland which
                          influences metabolism
                  e.      e.       Adrenocorticotropic hormone (ACTH)--stimulated to release by RF
                          in hypothalamus and by stress, causes cortex of adrenal gland to produce and
                          release hormones
                  f.      f.       Follicle stimulating hormone (FSH) -- in females stimulates
                          development of eggs each month and simulates ovaries to produce estrogen; in
                          males FSH stimulates production of sperm, FSH production controlled by
                          hypoth. in response to estrogen and testosterone levels (neg. feedback)


                   g.     g.        Luteinizing hormone (LH)--in females works w/ estrogen to stimulate
                          ovaries to release ovum and prepare the uterus for implantation of egg, in males
                          stimulates testes to produce testosterone
            3.     3.      Posterior lobe -- composed of neuroglial cells that support terminal axons from
                   hypoth., does not produce hormones but stores two hormones produced by nerve cells
                   of hypothalamus
                   a.     a.        Oxytocin (OH) --stimulates contraction of smooth muscle of uterine
                          walls, stimulates cells around mammary ducts to contract leading to ejection of
                          milk; OT levels rise by positive feedback from uterine contraction (until baby is
                          delivered) and nursing (milk ejection plus rapid recovery of uterine muscles)
          b.     b.       Antidiuretic hormone (ADH) --regulates fluid balance in body by
                 increasing water reabsorption by kidneys, thus producing less urine; release
                 controlled by hypoth. which contains osmoreceptors stimulated by increasing
                 blood concentrationººADH production by hypoth. ºº transported to post.
                 pituitary and released ººkidneys reabsorb water and dilute blood concentration;
                 inhibited by excess water; also helps maintain blood pressure by stimulating
                 smooth muscle in walls of arterioles to contract in process called
                 vasoconstriction

B.   B.    THYROID GLAND
     1.   1.      located below larynx in front of trachea, consists of two lobes, composed of
          glandular epithelium w/ outer C.T. capsule, divided into smaller regions called follicles
          where hormones are actually produced and secreted

     2.   2.       thyroxine and triiodothyronine (T4 and T3) --stimulate to release by TSH due
          to low levels of T3 and T4 in blood, affect metabolism by
          a.      a.       8 protein synthesis
          b.      b.       8 fat metabolism
          c.      c.       8 carbohydrate metabolism
          d.      d.       8 heart rate and ventilation rate
          e.      e.       8 actions of nervous system
     3.   3.       iodine is essential in diet for these hormones to be produced
     4.   4.       calcitonin --reduces calcium and phosphate levels in blood by decreasing
          osteoclast activity and reabsorption by kidney
C.   C.    PARATHYROID GLAND
     1.   1.       located posterior to the thyroid gland
     2.   2.       produces parathyroid hormone (PTH) --increase blood calcium by
          a.      a.       8 osteoblast activity
          b.      b.       8 calcium and phosphate reabsorption in kidneys

D.   D.     ADRENAL GLANDS
     1.   1.        located anterior to kidneys, divided into two distinct glands, the adrenal
          medulla and adrenal cortex
     2.   2.        Adrenal medulla--outer region of adrenal gland, composed of modified nervous
          tissue, releases hormones that cause changes like the sympathetic nervous system (fight
          or flight or frolic)
          a.       a.       epinephrine and norepinephrine--stimulated to release by sympathetic
                   system
                   (1).    (1).    8 lipid metabolism
                   (2).    (2).    8glycogenolysis--conversion of glycogen to glucose
                   (3).    (3).    vasoconstriction or vasodilation
                   (4).    (4).    8 heartrate and enlargement of airways
     3.   3.        Adrenal cortex--glandular epithelium forming inner layers of adrenal glands,
          produces steroid hormones from cholesterol
          a.       a.       glucocorticoids-- stimulated to release by ACTH; include cortisol and
                   cortisone; function to increase blood glucose by:
                   (1).    (1).    converting AA to glucose
                   (2).    (2).    stimulating gluconeogenesis in liver
                   (3).    (3).    also inhibits immune response and inflammation by stabilizing
                           lysosomes
          b.       b.       mineralcorticoids--functions to maintain fluid balance by affecting
                 dissolved ions, most important one is aldosterone which acts on the kidneys to
                 (1).    (1).     retaining Na+ and excreting K+ (the body is intolerant of wide
                         fluctuations in these two minerals
                 (2).    (2).     this helps the body conserve water and maintain blood pressure,
                         stimulus for release is low blood volume or high K+
          c.     c.       androgens and estrogens--sex hormones produced in both sexes but in
                 different amounts

E.   E.    PANCREAS
     1.   1.       gland located in abdominal cavity behind stomach, has both endocrine and
          exocrine functions, Islets of Langerhans are groups of cells within pan. that produce and
          release 2 hormones w/ opposite effects
     2.   2.       glucagon--stimulated to release by 9 in blood glucose of 8 in AA, functions 8
          glucose by:
          a.      a.       converting glycogen to glucose in liver
          b.      b.       8 breakdown of triglycerides to free fatty acids in an effort to spare
                  glucose
          c.       c.       high blood glucose feeds back to % cells inhibiting
                   further release of glucagon
     3.   3.        insulin--stimulated to release by 8 blood glucose, has a
          half life of 40 minutes, reduces glucose levels by:
          a.       a.       stimulating glucose uptake by most cells except
                   nervous, renal, and blood cells
          b.       b.       inhibiting fat breakdown
          c.       c.       stimulating protein synthesis
     4.   4.        diabetes mellitus--" sweet siphon", diabetics produce
          copious amounts of urine containing glucose, normal urine
          contains none, this leads to pathogenic conditions
          a.       a.       excess water loss as glucose in urine draws water
                   out of body
          b.       b.       loss of electrolytes in urine, small changes are
                   dangerous
          c.       c.       8 protein catabolism, most proteins are structural
                   or functional
          d.       d.       8 lipolysisºº8 fatty acids and an acid condition in
                   body, acetone breath from ketone bodies, fatty acid
                   deposition on walls of arteries

F.   F.    PINEAL GLAND
     1.   1.       located superior to the thalamus in cranial cavity
     2.   2.        melatonin -- functions are being studied but is available
          in health food stores as a diet supplement
     3.   3.       thought to inhibit FSH and LH secretion by ant. pituitary
     4.   4

								
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