The Endocrine System

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The Endocrine System

• Chapter 18

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Information System

• Works much like the nervous system.except
• The nervous system uses nerves to conduct
  messages.
• The Endocrine system uses blood vessels as
  information channels.

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Glands

• Release Messengers , in the form of hormones,
  into the bloodstream.
• HormonGreekto urge on.

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Hormones

• Regulate the functions of an organism.in this
  case.humans.
• Hormones produce their effects by binding to
  receptors.
• A receptor is a site of recognition on target
  tissue---Lock and Key effect.
• Each hormone has its own receptor.

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For Instance

• Thyroid stimulating hormoneits target tissue is
  the thyroid gland. The thyroid gland has a
  receptor for TSH. TSH would not work on the
  pancreas because the pancreas do not have
  receptors for TSH.

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Endocrine vs. Exocrine

• Endocrine GlandsEndowithin and crineto
  secrete. Endocrine glands are ductless. They
  secrete hormones directly into the bloodstream.
• Exocrine send their chemical substances into
  ducts which lead to the outside (exo-) of the
  body. Sweat glands and mammary glands.

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Endocrine Glands

• Thyroid
• Parathyroid
• Adrenal
• Pancreas
• Pituitary

• Ovaries
• Testes
• Pineal
• Thymus

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Pineal and Thymus

• Pineal Located in the central part of brain.
• Said to secrete Melatonin.
• Melatonin---sleep, skin pigmentation.
• Pineal is also referred to as your internal
  clock.

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Thymus

• Located in the mediastinal area.
• Contains lymphatic tissue and T cell lymphocytes.
• Produces Thymosin.
• Important in immunity.
• Shrinks as we age.

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Important Distinction

• Not all hormones are produced by endocrine
  glands.
• Kidney Erythropoietin.
• Gastrointestinal tract Gastrin, secretin and
  cholecystokinin.
• Skin Vitamin D.
• Placenta HCG.
• Prostaglandinsvarious sites.

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Thyroid Gland

• Bi-lobed.
• Located on either side of the trachea.
• Lobes joined by the isthmus.

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Thyroid Function

• Two hormones T3 and T4
• Triiodothyronine and Tetraiidothyronine.
• Both are made from iodine.
• Have to have T3 and T4 in order to maintain
  normal metabolism.
• Where does iodine come from?

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What if you have no iodine?

• TSH signals the thyroid gland to make T3 and
  T4.butT3 and T4 cannot be made because you have
  no iodine.but TSH keeps stimulating the
  thyroidgoiter.

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More Thyroid Hormones

• Calcitonin
• If calcium in the bloodstream is high, the
  thyroid secretes calcitonin.
• Calcitonin will remove calcium from the
  bloodstream and put it in the bones.
• If the opposite occursParathyroid hormone will
  take calcium from the bone and put it in the
  blood.

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Speaking of Parathyroid Hormone

• Parathyroid glandsfour small glands on the back
  of the thyroid.
• They secrete parathyroid hormone (PTH).
• PTH mobilizes calcium from the bones and puts it
  in the bloodstream when needed.
• Excellent example of homeostasis.

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Adrenal Glands

• One lies on top of each kidney.
• Two layers Cortex and Medulla.
• Each layer releases its own hormones.

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Adrenal Cortex

• Three hormones collectively called
  corticosteriods.
• 1. Glucocorticoids
• 2. Mineralocorticoids
• 3. Sex hormones

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Glucocorticoids

• Responsible for the metabolism of sugars, fats
  and proteins and antiinflammatory.
• A. Cortisol--Gluconeogenesis
• B. CortisonInflammatory conditions

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Mineralocorticoids

• Regulate electrolytes
• AldosteroneIncreases the reabsorption of sodium
  and stimulates the secretion of potassium.

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Sex Hormones

• Androgen (andr/omale)
• Estrogen
• Progestins
• Help maintain secondary sexual characteristics.
  Also produced in the ovaries and testes.

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The Medulla

• Secretes two types of catecholamine hormones
• 1. Epinephrine--Adrenalin
• 2. NorepinephrineAoradrenalin
• Both are sympathomimetic agents because they
  mimic the actions of the sympathetic nervous
  system.

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The Pancreas

• Located partially behind the stomach
• Islets of Langerhans

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Function

• The Islets of Langerhans produce two hormones
• 1. Insulinbeta cells
• 2. Glucagonalpha cells

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The Insulin Bus

• You MUST have insulin, in sufficient amounts, for
  the food you eat to get to your cells.
• I call this the insulin bus.
• If insulin is not produced, or produced in
  quantities that are insufficient, then the sugar
  you eat cannot catch a ride to the cells and
  the sugar just floats around.

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Diabetes

• Insulin Dependent
• Non-Insulin Dependent

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Glucagon

• When glucose levels are above normal, the excess
  is taken, by insulin, to the cells to be stored
  for later.
• It is stored as glycogen in the liver.
• Glucagon twin will be released into the
  bloodstream when glucose is low.
• Glucagon causes the stored glycogen to be
  converted back into glucose.

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Pituitary Gland

• Also called the hypophysis
• Small
• Pea-sized gland
• Located at the base of the brain
• Sits in a pocket called the sella turcica

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Two lobes

• Anterior lobeadenohypophysis.
• Posterior lobeneurohypophysis.
• The pituitary gland is known as the Master Gland.
• It is controlled by signals from the hypothalamus.

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Hypothalamus

• Secretes releasing and inhibiting hormones via
  capillaries to the pituitary gland.
• Tells it when to secrete more and when to hold
  back.
• And of course, each lobe of the pituitary
  secretes different hormones.

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Anterior/adenohypophysis

• GH
• TSH
• ACTH
• FSH and LH
• PRL
• MSH

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Posterior/neurohypophysis

• ADH
• Oxytocin

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Ovaries and Testes

• Ovaries secrete estradiol (an estrogen) and
  progesterone.
• Estradiol development and maintenance of
  secondary sexual characteristics.
• Progesterone preparation and maintenance of
  uterus in pregnancy.

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Testes

• Testosterone
• Androgen
• Stimulates and promotes the development of
  secondary sexual characteristics.

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When Things go Wrong!

• Too much hypersecretion
• Too little hyposecretion

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Graves Diseases Hyperthyroid Exophthalmos
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Congenital hypothyroidism
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Acromegaly
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Cushings Disease Adrenal
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Albinism
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TermsKnow for Thursday

• Aden/o
• Adren/o
• Gonad/o
• Pancreat/o
• Parathyroid/o
• Pituitar/o
• Thyr/o
• Andr/o

• Calc/o
• Cortic/o
• Crin/o
• Dips/o
• Estr/o
• Gluc/o
• Glyc/o
• Home/o

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More Terms for Thursday

• Insulin/o
• Kal/I
• Lact/o
• Myx/o
• Natr/o
• Phys/o
• Somat/o
• Ster/o

• Discussion on Thursdaysuffixes
• The difference between diabetes mellitus and
  insipidus.
• Cushings and Addision disease.
• Lab Tests