Endocrine System

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Endocrine System
2011-02-10 09:45:34
Endocrine System

Endocrine System
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  1. Hormones
    Chemical signals transported by the bloodstream that stimulate physiological responses in cells of another tissue or organ
  2. Compare Nervous System to the Endocrine System
    • Nervous System communicates through neurotransmitters and release signals through the synapse and effect specific areas.
    • Endocrine System communicate through hormones and release signals in bloodstream, effecting general areas.
  3. Endocrine Glands
    • Ductless glands that secrete hormones
    • Lots of capillaries to carry hormones
  4. Target Organs
    • Target organ cells have receptors specific to that hormone
    • Some hormones have target organs through the body, others have only one.
  5. Adenohypophysis
    Anterior pituitary: True gland
  6. Neurohypophysis
    Posterior Pituitary: neural tissue
  7. Pituitary gland is made of what two parts?
    Adenohypophysis and Neurohypophysis
  8. What chemicals does Neurohypophysis release?
    • Oxytocin is produced by neurons in the paraventricular nucleus.
    • Antidiuretic hormone (vasopressin) produced by neurons in the supraoptic nucleus
  9. Oxytocin
    • Receptor locations: mammary gland, uterus, and heart
    • Causes uterine contractions during labor
    • Allows letdown reflex during breastfeeding
    • Some role in orgasm
    • Some role in trust and empathy
  10. Antidiuretic Hormone or Vasopressin
    • Receptor locations: kidney, liver, and vasculature
    • Regulates water retention by kidneys
    • Ethanol is ADH antagonist
    • Increases blood pressure
  11. Diabetes Insipidus
    • Characterized by excessive thirst and excretion of lots of dilute urine
    • Typically caused by inability to make sufficient amounts of ADH
  12. How does Anterior Pituitary release hormones?
    • Neurosecretory neurons in hypothalamus release "releasing hormone"
    • RH enters hypophyseal portal system (small capillaries between hypothalamus and pituitary)
    • Anterior pituitary cells with receptors for that RH are activated and secrete tropic hormones into general circulation
  13. Prolactin
    • Stimulates milk production in mammary glands
    • Released after orgasm (refractory period?)
  14. Growth Hormone
    • Stimulated by GHRH
    • Inhibited by somatostatin
    • Widespread effects on body
    • Induces mitosis and cellular differentiation in cartilage, bone, muscle, and fat
    • Promotes protein synthesis, decreases protein metabolism
    • Promotes lipid release and metabolism to spare the proteins and carbohydrates for growth and brain function
    • Promotes electrolyte retention
  15. Factors Promoting GH Secretion
    • Stimulate GH:
    • Sleep
    • Vigorous exercises
    • Good nutrition
    • GOnadal hormones during puberty
  16. Factors Inhibiting GH Secretion
  17. Other Factor affecting GH Secretion
    GH stimulates IGF-I and II release from the liver, which prolongs GH's effects
  18. Growth Hormone in Childhood and Adolescence
    • Bone, cartilage, and muscle growth
    • Secret about 700 mg/day in adolescence
  19. Growth Hormone in Adulthood
    • Bone thickening and remodeling
    • Secrete about 400 mg/day
  20. Pituitary Gigantism
    Caused by a tumor in the pituitary gland that leads to excess GH secretion
  21. Acromegaly
    • Expansion of soft tissue and bones, often accompanies gigantism.
    • Due to excess GH secretion.
  22. Growth Hormone Deficiency
    • Short Stature
    • Delayed puberty
    • Slow muscular development
    • Causes: genetic mutation, pituitary tumor, radiation, trauma, or surgery to the head
  23. Growth Hormone Use in Athletes
    • In normal adults, GH causes increase in water retention, increase in connective tissue, decrease in fat
    • No increase in muscle strength
    • Recover faster from injury
    • Stamina may be decreased
  24. Growth Hormone in Livestock
    • GH is given to cows to increase milk production
    • Not legal to use GH in cows raised for beed or in poultry or pigs
    • rBST milk: higher IGF-I levels, more pus (sours faster), sometimes lower nutritional quality
  25. Tropic Hormones of Pituitary
    Causes target organ to release its own hormone
  26. Thyroid Gland
    • Largest endocrine gland
    • Reddish brown due to lots of blood flow
    • In response to thyroid stimulating hormone from the pituitary, it secretes "thyroid hormone"
    • Thyroxine or Tetraiodothyronine (T4)
    • Triiodothyronine (T3)
  27. Thyroid Hormones
    • Synthesized by iodine
    • Increase metabolic rate
    • Increase heart and respiratory rates
    • Increase heat production
    • TH levels in rise in cold environments
    • Promote alertness, growth hormone secretion, growth of bones, skin, hair, nails and teeth, development of fetal nervous system
  28. Histology of Thyroid
    • Follicular cells produce T3 and T4
    • C cells secrete calcitonin in response to high blood calcium levels (promotes bone formation)
  29. Goiter
    • Typically caused by iodine deficiency
    • People living in inland regions of developing countries are susceptible
    • Thyroid swells in attempt to capture more iodine
  30. Thyroid Hormone Excess
    Hyperthyroidism: fatigue, heat intolerance, hyperactivity, weight loss
  31. Thyroid Hormone Deficiency
    Hypothyroidism: fatigue, cold intolerance, joint pain, weight gain, bradycardia (slow heart rate)
  32. Ovaries
    • Estrogen, progesterone, some androgens, and inhibin secreted from granulosa and thecal cells
    • Hormones secreted in response to FSH and LH from pituitary
  33. Function of Estrogens
    • 3 estrogens: estradiol, estrone, and estriol
    • Promotes secondary sexual characteristics
    • Increase metabolic rate
    • Reduce muscle mass
    • Increase uterine growth
    • Increase bone formation
    • Influence mood, cognitive function, and libido
  34. Function of Progesterone
    • Prepares the body for pregnancy
    • Regulates immune response
    • Decreases anxiety
    • Probably neuroprotective effects
  35. Testes
    Interstitial (Leydig) cells secrete androgens in response to LH from pituitary
  36. Function of Androgens
    • Include testosterone and several weaker androgens (DHEA, DHT, and androstenedione)
    • Promote sperm production
    • Important for development of male genitalia
    • Inhibit fat storage
    • Promote muscle development
    • Influence aggression, libido, cognitive function
  37. Adrenal Cortex
    Outer "bark"
  38. Adrenal Cortex releases Steroid Hormones
    • Mineralocorticoids from zona glomerulosa
    • Glucocorticoids from zona fasciculata
    • Sex steroids from zona reticularis
  39. Mneralocorticoids (Aldosterone)
    • Promotes salt and water retention by kidney
    • Increases blood volume and blood pressure
  40. HPA Axis
    • Cortisol (primary human glucocorticoid) released when ACTH binds
    • Produces stress response by increasing alertness and blood glucose, inhibiting immune system, and affecting memory.
  41. Adrenal Sex Steroids
    • Androgens: small amounts of testosterone, DHT, and DHEA; a major source of androgens for females
    • Estrogens: small amounts of estradiol; important for postmenopausal women
  42. Congenital Adrenal Hyperplasia
    • Caused by dysfunction of one of the enzymes needed to produce glucocorticoids and mineralocorticoids
    • Result is overproduction of androgen
  43. Female CAH Patient
    Excess testosterone in prenatal development can lead to masculinized genitalia, infertility, masculinized behavour
  44. Adrenal Medulla
    • Inner "Core"
    • Modified part of sympathetic nervous system
    • Chromaffin cells release epinephrine and norepinephrine into the bloodstream when SNS neurons release Acetylcholine
  45. Effects of Epinephrine (adrenaline)
    • Similar effects as remainder of sympathetic nervous system
    • Increases heart rate and blood pressure, dilates airways, increases blood glucose levels, increases circulation to muscles, and inhibits digestion and reproduction