Endocrine System

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Endocrine System
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Endocrine and Exocrine

• Endocrine functions communication and control,
  via hormones
• Exocrine functions secrete products into ducts
  that empty on a surface or into a cavity

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Endocrine

• Secretes HORMONES into the blood
• Endocrine Organs are located throughout the body
  head, neck, chest, abdomen, pelvis.
• Endocrine secretions (hormones)bind to specific
  cells ( target organ cell) that have receptors
  for that specific hormone.

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Mechanisms of Hormone Action

• Two Major classes of hormones
• Protein Steroid
• Differ in mechanisms by which they influence
  target cells

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Protein Hormones

• Protein hormones serve as first
  messengers..that is they send message to a
  specific target organ for functions to take
  place. Then a number of chemical reactions
  occur. These reactions activate molecules inside
  the cellsecond messengers
• Second messengers provide communication within a
  hormones target cells.

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Steroid Hormones

• Pass directly through cell membrane
• Enters the nucleus of the cell
• Forms hormone receptor complex that acts on the
  DNA
• New protein is formed in the cytoplasm that
  causes a specific effect in the target cell

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Regulation of Hormone Secretion

• Controlled by homeostatic feedback
• Negative Feedback reverses the direction of
  change in a physiological system. Ex
  Pancreatic Insulin to lower blood sugar
• Positive Feedback amplifies physiological
  changes. Ex Oxytocin release during labor to
  advance birth

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Endocrine Disease

• Caused by
• Hypersecretion too much hormone secreted
• Hyposecretion too little hormone secreted.
• See Table 10-1, pages 302-303