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2014-04-10 11:04:28
endocrine system ch16
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  1. endocrinology
    study of hormones and endocrine organs
  2. endocrine system
    • acts with nervous system to coordinate and integrate activity of body cells
    • influences metabolic activities via hormones transported in blood
    • response slower but longer lasting than nervous system
  3. endocrine system overview of functions
    • reproduction
    • growth and development
    • maintenance of electrolyte, water, and nutrient balance of blood
    • regulation of cellular metabolism and energy balance
    • mobilization fo body defenses
  4. exocrine glands
    • nonhormonal substances (sweat, saliva) 
    • have ducts to carry secretion to membrane surface
  5. endocrine glands
    • produce hormones
    • lack ducts
    • empty contents directly into the blood
  6. name a neuroendocrine organ
  7. which organs have both endocrine and exocrine functions
    pancreas, gonads, placenta
  8. name some tissues and organs that produce hormones
    • adipose cells
    • thymus
    • cells int he walls of small intestine
    • stomach
    • kidneys
    • heart
  9. hormones
    • long distance chemical signals
    • travel in blood of lymph
  10. autocrines
    chemicals that exert effects on same cells that secrete them
  11. paracrines
    locally acting chemicals that affect cells other than those that secrete them
  12. are autocrines and paracrines considered part of the endocrine system
    no; because they are local chemical messengers
  13. what are the two main classes of hormones
    • amino acid-based hormones
    • steroids
  14. amino acid-based hormones
    amino acid derivatives, peptides, and proteins
  15. steroids
    • synthesized from cholesterol
    • gonadal and adrenocortical hormones
  16. target cells
    tissues with receptors for specific hormone
  17. hormones alter target cell ______
  18. hormones action on target cells may be to
    • change plasma membrane permeability and opening/closing ion channels
    • stimulate synthesis of enzymes
    • activate/deactivate enzymes
    • stimulate mitosis
    • induce secretory activity
  19. mechanisms of hormone action: water soluable hormones
    • [all amino acid-based hormones except thyroid hormone]
    • act on plasma membrane receptors
    • act via G protein second messengers
    • cannot enter the cell
  20. mechanisms of hormone action: lipid-soluable hormones
    • [steroid and thyroid hormones]
    • act on intracellular receptors that directly activate genes
    • can enter cell
  21. cAMP signaling mechanisms
    • 1. hormone binds to receptor
    • 2. recept activates G protein
    • 3. G protein activates adenylate cyclase
    • 4. adenylate cyclase converts ATP to cAMP
    • 5. cAMP activates protein kinases that phosphorylate proteins
  22. cAMP is rapidly degraded by enzyme
  23. what does Ca2+ do during second messenger systems
    • alters enzyme activity and channels or binds to regulatory protein calmodulin
    • calcium bound calmodulin activates enzymes that amplify cellular response
  24. intracellular receptors and direct gene activation (steroid and thyroid hormones)
    • 1. diffuse into target cells and bind ith intracellular receptors
    • 2. receptor hormone complex enters nucleus; binds to specific region of DNA
    • 3. prompts DNA transcription to produce mRNA
    • 4. mRNA directs protein synthesis
    • 5. promote metabolic activities or promote synthesis of structural proteins or proteins for export from cell
  25. target cell specificity
    • target cells must have specific receptors to which hormone binds for 
    • ex. ACTH receptors found only on certain cells of adrenal cortex;
    • ex. thyroxin receptors are found on nearly all cells of body
  26. target cell activation depends on 3 factors
    • blood levels of hormone
    • relative number of receptors on or in target cell
    • affinity of binding between receptor and hormone
  27. hormones influence number of their receptors, T or F
  28. up-regulation
    target cells form more receptors in response to low hormone levels
  29. down-regulation
    target cells lose receptors in response to high hormone levels
  30. how are blood levels of hormones controlled
    • by negative feedback systems
    • vary only within narrow, desirable range
  31. endocrine gland stimulated to synthesize and release hormones in response to
    • humoral stimuli
    • neural stimuli
    • hormonal stimuli
  32. humoral stimuli
    • changing blood levels of ions and nutrients directly stimulate secretion of hormones
    • ex. declining CA2+ in the blood stimulates parathyroid glands to secrete PTH, which cause CA2+ concentrations to rise, removing the stimulus (PTH stimulates osteoclasts)
  33. neural stimuli
    • nerve fibers stimulate hormone release
    • sympathetic nervous system fibers stimulate adrenal medulla to secrete catecholamines
  34. hormonal stimuli
    • hormones stimulate other endocrine organs to release their hormones
    • hypothalamic hormones stimulate release of most anterior pituitary hormones
    • anterior pituitary hormones stimulate targets to secrete still more hormones
    • hypothalamic-pituitary target endocrine organ feedback loop: hormones from final target organs inhibit release of anterior pituitary hormones
  35. ACTH
    adrenalcorticaltropic hormone
  36. nervous system modulation
    • nervous system modifies stimulation of endocrine glands and their negative feedback mechanisms (ex. under stress, hypothalamus and sympathetic nervous system activated)
    • nervous system can override normal endocrine controls
  37. hormones in the blood
    • circulate either free or bound.
    • (steroids and thyroid hormones are attached to plasma proteins; all others circulate without carriers)
  38. concentration of circulating hormone reflects
    • rate of release
    • speed of inactivation and removal from body
  39. hormones are removed from the blood by
    • degrading enzymes
    • kidneys
    • liver (half-life)
  40. what is half-life
    • time required for hormone's blood level to decrease by half
    • varies from fraction of a minute to a week
  41. onset of hormone activity (time)
    • some responses are immediate
    • some need hours to days (steroids)
    • some must be activated in target cells
  42. duration of hormone activity
    • limited
    • ranges from 10 seconds to several hours
    • effets may disappear as blood levels drop
    • some persist at low blood levels
  43. permissiveness
    one hormone cannot exert its effects without another hormone being present
  44. synergism
    more than one hormone produces same effects on target cell -> amplification
  45. antagonism
    • one or more hormones oppose action of another hormone. 
    • ex. glycagon and insulin
  46. the pituitary gland (hypophysis) has two major lobes:
    • posterior pituitary (lobe): neural tissue
    • anterior pituitary (lobe)(adenohypophysis): glandular tissue
  47. posterior pituitary lobe
    • downgrowth of hypothalamus neural tissue
    • neural connection to hypothalamus
    • nuclei of hypothalamus synthesize neurohormones oxytocin and antidiuretic hormone
    • neurohormones are transported to and stored in posterior pituitary
  48. anterior pituitary lobe
    • originates as outpocketing of oral mucosa
    • vascular connection to hypothalamus
    • hypophyseal portal system: primary capillary plexus, hypophyseal portal veins, secondary capillary plexus, carries releasing and inhibiting hormones to anterior pituitary to regulate hormone secretion
  49. oxytocin and ADH
    • composed of 9 amino acids
    • almost identical but differ in 2 amino acids
  50. oxytocin
    • strong stimulant of uterine contraction
    • released during childbirth
    • hormonal trigger for milk ejection
    • acts as neurotransmitter in brain
  51. ADH
    • antidiuretic hormone (vasopressin)
    • inhibits or prevents urine formation
    • regulates water balance
    • targets kidney tubules > reabsorb more water
    • release also triggered by pain, low blood pressure, and drugs
    • inhibited by alcohol, diuretics
    • high concentrations > vasoconstriction
  52. ADH disorders
    • diabetes insipidus
    • syndrome of inappropriate ADH secretion
  53. diabetes insipidus
    • ADH deficiency due to hypothalamus or posterior pituitary damage
    • must keep well-hydrated
  54. syndrome of inappropriate ADH secretion
    • retention of fluid, headache, disorientation
    • fluid restriction; blood sodium level monitoring
  55. list the anterior pituitary hormones
    • growth hormone (GH)
    • thyroid-stimulating hormone (TSH) or thryotropin
    • adenocorticotropic hormone (ACTH)
    • follicle stimulating hormone (FSH)
    • luteinizing hormone (LH)
    • prolactin (PRL)
  56. characteristics of anterior pituitary hormones
    • all are proteins
    • all except GH activate cyclic AMP second messenger systems at their targets
    • TSH, ACTH, FSH, LH are all tropic hormones meaning they regulate secretory action of other endocrine glands
  57. GH
    • growth hormone or somatotropin
    • direct ations o metabolism
    • increases blood levels of fatty acids, protein synthesis
    • decreases rate of glucose uptake and metabolism to conserve glucose
    • glycogen breakdown and glucose release to blood (anti insulin effect)
    • indirecti actions on growth
    • mediates growth via growth promoting proteins like insulin like growth factors
    • major targets: bone and skeletal muscle
    • chiefly regulated by hypothalamis hormones
    • ghrelin also stimulates release
  58. IGFs
    • insulin like growth factors
    • stimulate uptake of nutrients
    • formation of collagen and deposition of bone matrix
  59. growth hormone releasing hormone GHRH
    stimulates release
  60. growth hormone inhibiting hormone GHIH
    inhibits release
  61. ghrelin
    • hunger hormone
    • stimulates release of growth hormone
  62. thyroid stimulating hormone (thyrotropin)
    • produced by thyrotropic cells of anterior pituitary
    • stimulates normal development and secretory activity of thyroid
    • release triggered by thyrotropin-releasing hormone from hypothalamus
    • inhibited by rising blood levels of thyroid hormones that act on pituitary and hypothalamus
  63. regulation of thyroid hormone secretion
    hypothalamus stimulates anterior pituitary which stimulates thyroid glands which stimulates target cells.
  64. adrenocorticotropic hormone (ACTH) (corticotropin)
    • secreted by corticotropic cels of anterior pituitary
    • stimulates adrenal cortex to release corticosteroids
  65. gonadotropins
    • follicle stimulating hormone (FSH) and luteinizing hormone (LH)
    • secreted by gonadotrophs or anterior pituitary
    • FSH stimulates gamete (egg or sperm) production
    • LH promotes production of gonadal hormones
    • absent from the blood in prepubertal boys and girls
  66. release of gonadotropins
    • triggered by gonadotropin releasing hormone during or after puberty
    • suppressed by gonadal hormones (feedback)
  67. prolactin (PRL)
    • secreted by prolactin cells of anterior pituitary 
    • stimulates milk production
    • role in males not well understood
  68. regulation of prolactin (PRL)
    • primarily controlled by prolactin inhibiting hormone (PIH) (dopamine)
    • blood levels rise toward end of pregnancy
    • sucking stimulates PRL release and promotes continued milk production
    • hypersecretion causes inappropriate lactation, lack of menses, infertility in females, and impotence in males
  69. thyroid gland
    • two alteral lobers connected by median mass called isthumus
    • composed of follicles that produce glycoprotein thyroglobulin
    • colloid fills lumen of follicles and is precursor of thyroid hormone
    • parafollicular cells produce the hormone calcitonin
  70. thyroid hormone (TH)
    • actually two related compounds
    • affects virtually every cell in the body
    • major metabolic hormone
    • increases metabolic rate and heat production
    • regulation fo tissue growth and development
    • maintenance of blood pressure
    • bins to target receptors
  71. negative feedback regulation of TH
    • rising TH levels provide negative feedback inhibition on release of TSH
    • hypothalamic thyrotropin releasing hormone can overcome negative feedback during pregnancy or exposure to cold
  72. calcitonin
    • produced by parafollicular cells
    • antagonist to parathyroid hormone (PTH)
    • at higher than normal doses inhibits osteoclast activity and release of CA2+ from bone matrix, and stimulates CA2+ uptake and incorporation into bone matrix
  73. parathyroid glands
    • four to eight tiny glands embeeded in posterior aspect of thyroid
    • contain oxyphil cells and parathyroid cells that secrete PTH or parathromone
    • PTH most important hormone in CA2+ homeostasis
  74. which hormone is the most important for maintaining CA2+ homeostasis
    parathyroid hormone PTH
  75. functions of the parathyroid glands
    • stimualtes osteoclasts to digest bone matrix and release Ca2+ to blood
    • enhances reabsorption of CA2+ and secretion of phosphate by kidneys
    • promotes activation of vitamin D (by kidneys); increases absorption of Ca2+ by intestinal mucosa
  76. rising Ca2+ in the blood inhibits ______ release
  77. adrenal (suprarenal) glands
    • paired pyramid shaped organs atop kidneys
    • structural and functionally are two glands in one: adrenal medulla and adrenal cortex
  78. adrenal medulla
    nervous tissue; part of sympathetic nervous system
  79. adrenal cortex
    three layers of glandular tissue that synthesize and secrete corticosteroids
  80. three layres of adrenal cortex
    • zona glomerulosa -mineralocorticoids
    • zona fasciulata - glucocorticoids
    • zona reticularis - gonadocorticoids
  81. mineralocorticoids
    • regulate electrolytes in ECF
    • importance of electrolytes Na+ and K+ is to generate action potentials
    • aldosterone most potent mineralocorticoid: stimualtes Na+ reabsorption and water retention by kidneys and eliminates K+
  82. what inhibits aldosterone
    caffeine, making you pee a lot
  83. release of aldosterone is triggered by
    • decreasing blood volume and blood pressure
    • rising blood levels of K+
  84. mechanisms of aldosterone secretion
    look @ powerpoint slide
  85. aldosteronism
    • hypersecretion due to adrenal tumors
    • hypertension and edema due to excessive Na+
    • excretion of K+ leading to abnormal function of neurons and muscle
  86. glucocorticoids
    • keep blood glucose levels relatively constant
    • maintain blood pressure by increasing action of vasoconstrictors
    • cortisol (hydrocortisone) only one in significant amounts found in humans
    • cortisone
    • corticosterone
  87. glucocorticoids: cortisol
    • released in response to ACTH, patterns of eating and activity and stress
    • prime metabolic effect is gluconeogenesis, formation of glucose form fats and proteins
    • saves glucose for brain
    • enhances vasoconstriction, rise in blood pressure to quickly distribute nutrients to cells
  88. gonadocorticoids (sex hormones)
    • most weak adrogens converted to testosterone in tissue cells, some to estrogens
    • may contribute to onset of puberty, appearance of secondary sex characteristics, sex drive in women, estrogens in postmenopausal women
  89. hypersecretions of gonadocorticoids
    • adrenogenital sndrome (masculinization)
    • not noticable in adult males
    • in females: beard, masculine pattern of body hair,
  90. adrenal medulla
    • medullary chromaffin cells synthesize epinephrine (80%) and norephinephrine (20%)
    • effects: vasoconstriction, increased heart rate, increased blood glucose levels, blood diverted to brain, heart, and skeletal muscle
    • response is brief
    • epinephrine stimulates metabolic activities, bronchial dilation, and blood flow to skeletal muscles and heart
    • norephinephrine influences peripheral vasoconstriction and blood pressure
  91. pineal gland
    • small gland hanging from roof of third ventricle
    • pinealocytes secrete melatonin, derived by seratonin
    • melatonin may affect: day/night cycles, timing of sexual maturation, body temp, sleep, appetite, production of antioxidant and detoxification molecules in cells
  92. ancreas
    • triangular gland partillay behind sotmach
    • has both exocrine and endocrine cells
    • acinar cells (exocrine): produce enzymerich juice fo digestion
    • pancreative islets: contain endocrine cells alpha and beta
  93. alpha cells of the pancreas produce
    glucagon (hyerglycemic hormone)
  94. beta cells of the pancreas produce
    insulin (hypoglycemic hormone)
  95. glucagon
    • major target is the liver
    • causes increased blood glucose levels
    • effects include: glycogenolysis and gluconeogenesis
  96. glycogenolysis
    breakdown of glycogen to glucose
  97. gluconeogenesis
    • synthesis of glucose from lactic acid and non carbohydrates
    • release glucose to blood
  98. insulin
    • lowers blood glucose levels
    • enhances membrane transport glucose into fat and muscle cells
    • inhibits glycogenolysis and gluoneogenesis
    • participates in neuronal development and learning and memory
    • not needed for glucose uptake in liver, kidney, or brain
  99. insulin action on cells
    • activates tyrosine kinase enzyme receptor
    • cascade > increased glucose uptake
    • triggers enzymes to catalyze oxidation of glucose to ATP production, polymerize glucose to form glycogen, convert glucose to fat
  100. factors that influence insulin release
    • elevated blood glucose levels (primary stimulus)
    • rising blood levels of amino acids and fatty acids
    • release of acetylcholine by parasympathetic nerve fibers
    • hormones glucagon, epinephrine, growth hormone, thyroxine, glucocorticoids
    • somatostatin, sympathetic nervous system
  101. diabetes mellitus
    • due to hyposecretion (type 1) or hypoactivity (type 2) of insulin
    • blood glucose levels remain high causing nausea and higher blood glucose levels (fight or flight response)
    • glycosuria: glucose spilled into urine
    • fats used for cellular fuel > lipidemia. if severed > ketones from fatty acid metabolism > ketonuria and ketoacidosis
    • untreated ketoacidosis causes hyperpnea; disrupted heart activity and O2 transport, depression of nervous system, coma, and death possibly
  102. 3 signs of diabetes mellitus
    • polyuria: huge urine output; glucose acts as osmotic diuretic
    • polydipsia: excessive thirst; from water loss due to polyuria
    • polyphagia: excessive hunger and food consumption; cells cannot take up glucose and are starving
  103. hyperinsulinism
    • excessive insulin secretion
    • causes hypoglycemia (low blood glucose levels, anxiety, nervousness, disorientation, even death)
    • treated by sugar ingestion
  104. ovaries and placenta
    • gonads produce steroid sex hormones
    • ovaries produce estrogens and progesterone
    • placenta secretes astrogens, progesterone, and hu man chorionic gonadotropin (hCG)
  105. what is the significance of human chorionic gonadotropin hCG
    its presence indicates pregnancy
  106. testes
    • produce testosterone
    • initiates maturation of male reproductive organs
    • causes appearance of male secondary sexual characteristics and sex drive
    • necessary for normal sperm production
    • maintains reproductive organs in functional state
  107. adipose tissue
    • leptin: appetite control; stimulates increased energy expenditure
    • resistin: insulin antagonist
    • adiponectin: enhances sensitivity to insulin
  108. enteroendocrine cells of gasterointestinal tract
    • gastrin: stimulates release of HCl
    • secretin: stimulates liver and pancreas
    • cholecystokinin: stimulates pancreas, gallbladder, and hepatopancreatic sphincter
    • serotonin: acts as paracrine
  109. heart secretes
    • atrial natriuretic peptide (ANP)
    • decreases blood Na+ concentration, which decreases blood pressure and blood volume
  110. kidneys secrete
    • erythropoietin: signals production of red blood cells
    • renin: initiates the renin angiotensin aldosterone mechanism
  111. skeleton secretes
    osteocalcin: prods pancreas to secrete more insulin, restricts fat storage, activated by insulin, low levels of osteocalcin in type 2 diabetes
  112. skin secretes
    cholecalciferol: precursor of vitamin D
  113. thymus secretes
    • thymulin
    • thymopoietins
    • thymosins
    • all of these involved i normal development of T lymphocytes in immune response
    • classified as hormones but act as paracrines