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The Endocrine System.ppt

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					The Endocrine System
• The endocrine system is a collection of glands
  that secrete chemical messages we call
  hormones.
• The vertebrate endocrine system consists of
  glands (pituitary, thyroid, adrenal), and diffuse
  cell groups scattered in epithelial tissues.
• ductless, which means that their secretions
  (hormones) are released directly into the
  bloodstream and travel to elsewhere in the
  body to target organs, upon which they act.
The roles of hormones in selecting target cells and delivering the hormonal message. Images
from Purves et al., Life: The Science of Biology, 4th Edition, by Sinauer Associates
(www.sinauer.com) and WH Freeman (www.whfreeman.com), used with permission.
           Classification

• Hormones are grouped into three
  classes based on their structure:
• steroids
• peptides
• amines
              Steroids
• Steroids are lipids derived from
  cholesterol
• Steroid hormones are secreted by the
  gonads, adrenal cortex, and
  placenta.
                       Sex Steroids
• Natural sex steroids are made by the (ovaries or testes)[3], by
  adrenal glands, or by conversion from other sex steroids in other
  tissue such as liver or fat.

• Sex steroids include:
androgens: Mainly male hormones
   –   testosterone
   –   androstenedione
   –   dihydrotestosterone
   –   dehydroepiandrosterone
   –   anabolic steroids
estrogens: mainly female hormones
   – estradiol
   – estrone
   – estriol
progestagens: mainly female hormones
   – progesterone
   – progestins
           Corticosteroid
• Glucocorticoids such as cortisol control
  carbohydrate, fat and protein
  metabolism and are anti-inflammatory.

• Mineralocorticoids such as
  aldosterone control electrolyte and
  water levels, mainly by promoting
  sodium retention in the kidney.
          Anabolic steroid
• Anabolic steroids, or anabolic-
  androgenic steroids (AAS), are a class
  of steroid hormones related to the
  hormone testosterone.
• They increase protein synthesis within
  cells, which results in the buildup of
  cellular tissue (anabolism), especially in
  muscles.
    Anabolic steroids can cause
      many adverse effects
• the most common being elevated blood
  pressure, especially in those with pre-
  existing hypertension, and harmful
  changes in cholesterol levels,
• have been shown to alter fasting blood
  sugar and glucose tolerance tests
• increase the risk of cardiovascular disease
  or coronary artery disease
  Anabolic steroids can cause
    many adverse effects
• Acne is fairly common due to
  stimulation of the sebaceous glands by
  increased testosterone levels.
• can accelerate the rate of premature
  baldness for males who are genetically
  predisposed, but testosterone itself
  can produce baldness in females.
• High doses of oral anabolic steroid
  compounds can cause liver damage
                  Peptides
• Peptides are short chains of amino acids; most
  hormones are peptides. They are secreted by
  the pituitary, parathyroid, heart, stomach,
  liver, and kidneys.
                  Amines
• Amines are derived from the amino acid
  tyrosine and are secreted from the thyroid
  and the adrenal medulla.
    The major human endocrine glands
                include
•   the hypothalamus and pituitary gland
•   the thyroid gland
•   the pancreas
•   the adrenal glands
•   the gonads or sex organs
•   the pineal gland
  Hypothalamus and Pituitary gland
• The pituitary gland is called the “master
  gland” but it is under the control of the
  hypothalamus.
• important to the female menstural cycle,
  pregnancy, birth, and lactation (follicle-
  stimulating hormone (FSH) & leutinizing
  hormone (LH) )
• antidiuretic hormone or ADH - helps prevent
  excess water excretion by the kidneys
• endorphins, which belong to the category of
  chemicals known as opiates and serve to
  deaden our pain receptors.
  – The natural response to rub an injured area, such
    as a pinched finger, helps to release endorphins in
    that area.
               Thyroid Gland
• regulate metabolism, therefore body
  temperature and weight
• contain iodine, which the thyroid needs in
  order to manufacture these hormones
  – person lacks iodine in his/her diet, the thyroid
    cannot make the hormones, causing a deficiency
                the pancreas

• Ducted gland - secreting digestive enzymes
  into the small intestine
• Ductless gland - the islets of Langerhans
  secrete insulin and glucagon to regulate the
  blood sugar level
               the adrenal glands
• sit on top of the kidneys
• consist of two parts, the outer cortex and the inner
  medulla
• medulla secretes epinephrine (= adrenaline) and
  other similar hormones in response to stressors
  such as fright, anger, caffeine, or low blood sugar
• The cortex secretes corticosteroids such as
  cortisone, well-known as being anti-inflammatory,
  thus are prescribed for a number of conditions
       the gonads or sex organs
• the female ovaries and male testes (singular =
  testis) secrete hormones
• is controlled by pituitary gland hormones
• both sexes make some of each of the
  hormones
  – male testes secrete primarily androgens including
    testosterone
  – Female ovaries make estrogen and progesterone
• baby’s placenta also secretes hormones to
  maintain the pregnancy
                 pineal gland

• located near the center of the brain in humans
• stimulated by nerves from the eyes
• secreted melatonin at night when it’s dark
  – secretes more in winter when the nights are
    longer
  – Melatonin promotes sleep (makes you feel
    sleepy). It also affects reproductive functions by
    depressing the activity of the gonads
                pineal gland
• it affects thyroid and adrenal cortex functions.
• SAD or seasonal affective disorder
  (syndrome) is a disorder in which too much
  melatonin is produced, especially during the
  long nights of winter, causing profound
  depression, oversleeping, weight gain,
  tiredness, and sadness.

				
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posted:7/19/2012
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