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					Chapter 45 ~
 Homeostasis and
 the Endocrine
 System
                       Endocrine System
   Endocrine system: consists of glands
    that release hormones into the blood
   Endocrine glands~ ductless hormone
    secreting glands
   Hormones~ chemical signals that are
    transported in blood (communicates
    regulatory messages) (Option H)
   Target cells~ body cells that respond
    to specific hormone (Option H)
   Feedback mechanisms
    Homeostasis and Negative Feedback
 Homeostasis = maintaining the
    internal environment of the body
    within limits (a steady state).
   Negative feedback maintains
    homeostasis
     – Level of the hormone has an
        effect that controls the
        hormone’s secretion
          Ex. If ADH levels are high,
           secretion of ADH slows.
          If ADH levels are low,
           secretion of ADH increases.




                            http://health.howstuffworks.com/adam-2000
             The Hypothalamus
 Brain  Region that
  links nervous and
  endocrine system.
 Controls the pituitary
  gland (the body’s
  “master gland”
         Hormone Examples: Insulin and Glucagon

 Islets   of
    Langerhans–
    clusters of endocrine
    cells in pancreas
     – Alpha cells:
          •glucagon~ raises blood
          glucose levels
     – Beta cells:          •insulin~
          lowers blood glucose levels
   Negative feedback!.

   http://video.yahoo.com/video/play?vid=11116902
    82&fr=yfp-t-501
                               Diabetes mellitus
 Blood  glucose
  homeostasis is NOT
  effectively maintained in
  diabetes
 How the disease was
  named:
   – Greek diabainein (to
     pass through), refers
     to excessive urination
     of diabetics.
   – Latin mellitus (honey-
     sweet)
     mellitus-5
                    http://www.healthline.com/galecontent/diabetes-




Two              types:
– Type I diabetes
  mellitus
    Onset: childhood

    autoimmune
     disorder (immune
     system destroys
     beta cells)
    insulin-dependent
     (Beta cells produce
     insufficient insulin)
    Insulin injections
     required
                   http://www.hivandhepatitis.com/hep_c/hepc_news_insulin.html




– Type II diabetes
  mellitus
     Onset: later in life
      (usually after childhood
     non-insulin-dependent
     reduced responsiveness
      to insulin (insensitivity)
     Can usually be
      controlled with low
      carb diets (insulin
      injections usually not
      needed)
End of IB

                   Vertebrate Endocrine System
    http://www.youtube.com/watch?v=rS7SM4vzs18

   Tropic hormones ~ a hormone that has another
    endocrine gland as a target
   Hypothalamus~pituitary
   Pituitary gland
   Pineal gland
   Thyroid gland
   Parathyroid glands
   Thymus
   Adrenal glands
   Pancreas
   Gonads (ovary, testis)

   http://health.howstuffworks.com/adam-200091.htm
             The Anterior Pituitary
   Anterior pituitary hormones:
     – Growth (GH)~bones
         √gigantism/dwarfism
         √acromegaly (abnormal growth of bones in head, hands, feet in
           adults)
     – Prolactin (PRL)~mammary glands; milk production
     – Follicle-stimulating (FSH) & Luteinizing (LH)~ gonadotropins
       (affect ovaries/testes)
     – Thyroid-stimulating (TSH)~ stimulates thyroid gland
     – Adrenocorticotropic (ACTH)~ stimulates adrenal cortex to secrete
       hormones
     – Melanocyte-stimulating (MSH)– regulates pigmented cells, fat
       metabolism
     – Endorphins~natural ‘opiates’; brain pain receptors
             The posterior pituitary

   The posterior pituitary:
   Oxytocin~
         uterine muscle contraction
    during childbirth and mammary
    gland milk secretion
   Antidiuretic (ADH)~
         retention of water by
    kidneys
      The pineal, thyroid, & parathyroid glands
 Melatonin~ pineal gland;
  biological rhythms

 Thyroid       hormones:
        Calcitonin~
  lowers blood calcium (opposite effects of
  PTH—see below
        Thyroxine~
          regulates metabolic processes
          (speeds up metabolism)

 Parathyroid          hormone
  (PTH)~           raises blood calcium
  (reabsorption in kidneys, release of
  calcium from bone)
                         The adrenal glands
   Adrenal medulla
    (catecholamines):
    •epinephrine & norepinephrine~
          increase basal metabolic rate
    (blood glucose and pressure)




                                          Adrenal cortex (corticosteroids):
                                                   •glucocorticoids (cortisol)~ raise
                                          blood glucose
                                                   •mineralocorticoids (aldosterone)~
                                          reabsorption of Na+ and K+, and water
                       The gonads
 Steroid     hormones:
  precursor is cholesterol

 androgens             (testosterone)~
  sperm formation; male secondary sex
  characteristics; gonadotropin

 estrogens                                         QuickTime™ and a
                                                  Cinepak decompressor
  (estradiol)~uterine lining growth; female   are needed to see this picture.

  secondary sex characteristics;
  gonadotropin

 progestins
       (progesterone)~uterine lining
  growth and maintenance
Local regulators: cells adjacent to or near point of secretion


   Growth   factors ~
        proteins for cell proliferation
   Nitric oxide (NO) ~
        neurotransmitter; cell destruction; vessel
        dilation
   Prostaglandins ~
        modified fatty acids secreted by placenta and
        immune system; cause uterine contractions
    during labor, induce inflammation

				
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posted:12/27/2012
language:English
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