THE ENDOCRINE SYSTEM

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THE ENDOCRINE SYSTEM

• Chapter 16

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OVERVIEW

• Group of unimpressive, discontinuous organs
• Coordinates and integrates body activity through
  the use of hormones produced in
• ductless glands

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• Differs from nervous system because its work is
  strictly chemical
• Exocrine glands use ducts to deliver their
  secretions

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Organs

• Pineal, hypothalamus, pituitary, thyroid,
  parathyroid, thymus, adrenal, pancreas, testis,
  ovary, placenta, tumors, cells within the
  digestive tract, heart, kidney, etc.

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Adrenal
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1
1
Pineal
Pituitary
1
2
Thyroid
2
Pancreas
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3
Ovaries
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4
9
Testes
Digestive hormones
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Thymus
4
Hypothalamus
1
5
Parathyroid
3
6
7
8
9
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tropic hormones
hypothalamus
thyroid-stimulating hormone (TSH)
antidiuretic hormone (ADH)
posterior pituitary
Thyroid gland
anterior pituitary
Kidney tubules
adrenocorticotropic hormone (ACTH)
oxytocin
Muscles of uterus
gonadotropic hormones follicle- stimulating horm
one (FSH) luteinizing hormone (LH)
melanocyte-stimulating hormone (MSH)
growth hormone (GH)
prolactin (PRL)
Adrenal cortex
Melanocyte in amphibian
Mammary glands in mammals
Bone and muscle
Ovary
Testis
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Hormones

• Chemicals released into extracellular fluids that
  regulate metabolic functions of other cells
• Ex growth, development, metabolism immune
  response, electrolyte water balance, blood
  pressure, RBC production

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• Hormones fall into one of 2 categories
• Amino-acid based most hormones in this
  category ex thyroxine, insulin, melatonin, ADH,
  etc.
• Steroid- (cholesterol based) ex sex hormones
  (estrogen, FSH, LH, testosterone), aldosterone

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• Function by binding to and influencing activity
  of a target cell (cell containing receptors for
  that hormone) ex most body cells have receptors
  for human growth hormone and thyroxine
• Provoke a secondary messenger activity
• OR
• Directly influence DNA activity of the cell

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• Once bound, hormones
• Change plasma membrane permeability
• Promote production of regulatory molecules
  enzymes
• Activate or deactivate enzymes
• Induce secretory activity of the cell

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• Control is by feedback mechanism
• Ex Negative Feedback
• Gland is stimulated due to low levels of hormone
• Hormone is released
• Hormone levels
  increase in
  bloodstream
• Increased levels
  deactivate gland

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Maintaining homeostasis
hormone 1
lowersbody condition
gland
specific body condition
raisesbody condition
gland
Negative FeedbackModel
hormone 2
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Controlling Body Temperature
Nervous System Control
Feedback
nerve signals
brain
sweat
dilates surfaceblood vessels
body temperature
brain
shiver
constricts surfaceblood vessels
nerve signals
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Regulation of Blood Sugar
Feedback
Endocrine System Control
insulin
body cells takeup sugar from blood
liver storessugar
reducesappetite
blood sugar level
liver releasessugar
triggershunger
glucagon
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Blood Osmolarity
Feedback
Endocrine System Control
ADH
increasedwaterreabsorption
increasethirst
blood osmolarity blood pressure
increasedwater saltreabsorption
renin
aldosterone
angiotensin
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Regulation of Blood Calcium
Feedback
Endocrine System Control
calcitonin
? kidney filters Ca
Ca depositedin bones
high
blood calcium level(10 mg/100mL)
? Ca uptakein intestines
low
activated Vitamin D
parathyroid
? kidney reabsorbs Ca
bones release Ca
PTH
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Female reproductive cycle
Feedback
eggmatures is released(ovulation)
builds up uterus lining
estrogen
progesterone
fertilized egg
FSH LH
maintainsuterus lining
HCG
pregnancy
progesterone
GnRH
corpus luteum breaks down progesterone drops
menstruation
maintainsuterus lining
hypothalamus
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• Control falls into one of 3 categories
• Hormonal stimuli Ex FSH from pituitary
  stimulates ovary to release progesterone and
  estrogen this in turn shuts down FSH rhythm

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• Humoral stimuli Ex blood sugar levels
  stimulate pancreas to release insulin this
  lowers sugar levels which in turn reduces insulin
  production

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• Neural stimuli Ex stress triggers adrenal
  gland to release adrenaline

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• Organs/Hormones
• Anterior Pituitary HGH, TSH, ACTH, FSH, LH,
  PRL
• Hypothalamus oxytocin, ADH
• Thyroid thyroxine, calcitonin
• Parathyroid PTH

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• Adrenal glucocorticoids, androgens,
  aldosterone, adrenaline
• Pancreas insulin, glucagon
• Gonads testosterone, estrogen, progesterone
• Pineal melatonin
• Thymus thymopoietin, thymosin

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Goiter

• Iodine deficiency causes thyroid to enlarge as it
  tries to produce thyroxine

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Robert Wadlow 1918-1940 8' 11"
Excessive HGH
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Hyperthyroidism
Graves - hyperthyroid
hypothyroidism
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Cushings Disease