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Other Endocrine Glands

thyroid gland - found right below Adam’s apple in the neck 

  • promotes growth/brain development
  • responsible for metamorphosis in amphibians
  • calcitonin - lowers blood calcium level
  • also releases triiodothyronine (T3) and thyroxine (T4)

parathyroid glands - 4 small glands attached to the thyroid gland 

  • stimulates release of calcium from bones
  • parathyroid hormone (PTH) - 1 of 2 hormones humans can’t live w/o
    • released in response to falling calcium levels
  • osteoclasts (bone cells) stimulated to release calcium
  • kidneys stimulated to reabsorb calcium in urine by vitamin D

adrenal glands - found above kidneys, contains adrenal medulla (inside), adrenal cortex (outside) 

  • adrenal medulla - receives neural info from sympathetic division
    • secretes epinephrine/norepinephrine
    • produces fight or flight response due to sympathetic nerves
  • adrenal cortex - produces steroids (called corticosteroids)
    • maintains glucose levels, stimulates gluconeogenesis
    • glucocorticoids - breaks down muscle proteins into amino acids, amino acids into glucose
    • aldosterone - 1 of 2 hormones humans can’t live w/o, stimulates kidneys to reabsorb Na+ and secrete K+

pancreas - located next to stomach, connected to duodenum 

  • secretes bicarbonate and enzymes into small intestine
  • islets of Langerhans - secretes insulin in beta cells, glucagon in alpha cells
  • type I diabetes - lacking insulin-secreting cells, but have insulin injections
  • type II diabetes - cells have reduced sensitivity to insulin
    • can only be helped by diet
  • insulin stimulates absorption of glucose
  • glucagon stimulates hydrolysis of glycogen >> antagonistic to insulin

other endocrine glands - 

  • molting/metamorphosis used for growth since exoskeletons don’t expand
    • brain hormone secreted >> ecdysone produced in thorax >> molting
    • juvenile hormone used up >> metamorphosis no longer inhibited
  • sex steroids - estrogen/progesterone in females, testosterone in males
    • androgens - determines male sex characteristics, overcomes the default female setting in mammals
    • estrogen - determines female sex characteristics, overcomes the default male setting in birds
  • pineal gland - aka “third eye”, secretes melatonin to regulate amount of sleep
    • maintains sleep, seasonal changes during migration, hibernation, mating
  • thymus - produces T cell lymphocytes
    • found in front of chest

endocrine-disrupting chemicals - low concentrations of target cells in blood 

  • small change in concentration >> big changes in effect on organ
  • agonist - chemical that mimic hormone
    • can bind to receptor proteins
  • antagonist - doesn’t mimic hormone, but stops hormones from binding
Subject: 
Biology
Subject X2: 
Biology

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