Functional Organization of the Endocrine System

• Endocrine Glands secrete hormones called chemical messengers
• The endocrine system with the regulated release of chemical messenger modulate activity in the body.
• Exocrine glands secrete material that are carried by ducts to the epithelial tissue.
• NS vs ES

  both are communication system but differ in target cell.
• NS - direct; Action potential - secrete neurotransmitter - synapse to target cell.
• ES - Indirect; secrete hormones in Blood stream
• Hormones are transported to bloodstream to target tissues which stimulate the response
• Autocrine stimulate the ceel that originally secreted it
• Autocrine are secreted by cells in a local area; influences the activity of the same cell from which it was secreted.
• Produced by a wide variety of tissues and secreted into extracellular fluid; has a localized effect on nearby tissues this is paracrine.
• Neurotransmitter are produced by neurons; secreted into a synaptic cleft by presynaptic nerve terminals; travels short distances; influences postsynaptic cells.
• Paracrine act locally in nearby cell.
• Neurotransmitters activate adjacent cells.
• Endocrine are secreted into the blood by specialized cells; travels some distance to target tissues; results in coordinated regulation of cell function; called hormones.
• Endocrine are hormones secreted into blood and travel to target tissue.
• Somatostatin, histamine, eicosanoids are Paracrine chemical messenger
• Eicosanoids (prostaglandins, thromboxanes, prostacyclins, leukotrienes) are Autocrine chemical messenger.
• Acetylcholine, epinephrine are neurotransmitter chemical messenger
• Thyroid hormones, growth hormone, insulin, epinephrine, estrogen, progesterone, testosterone are Endocrine chemical messenger
• Set into motion is hormone
• CHM - HORMONE - TRAVEL TO TARGET TISSUE - RECEPTOR - COORDINATED RESPONSE
• Humoral Stimuli - fluids of the body - blood; metabolites & molecules - directly stimulate the release of some hormones - in which has cell receptors in certain substance in blood to secrete these hormones.
• glucose, Ca2+, and Na+ can stimulate hormone secretion. When the blood level changes, the hormone is released in response to the molecule’s concentration. example of a humoral regulated hormone is the Ca2+-regulation hormone, parathyroid hormone (PTH).
• Neural Stimuli - Neuron release neurotransmitter that stimulate the cell to secrete hormone.

  Example: stress or exercise, stimulate the adrenal gland to secrete epinephrine and norepinephrine into the bloodstream making heart beat faster and increased blood flow.
• Hormones released by a neuron are neuropeptides.
• Some neuropeptides stimulate hormone secretion from other endocrine cells and are called releasing hormones, a term usually reserved for hormones from the hypothalamus.
• when a neuron releases a neurotransmitter at a synapse to stimulate a hormone’s secretion, it is considered a neural stimulus.
• when a neuron releases a neuropeptide hormone into the blood, which stimulates another hormone’s secretion, it is considered a hormonal stimulus.
• hormonal stimuli occurs when hormone stimulate the secretion of other hormones.
• Hormones of the hypothalamus stimulate the release of Tropic Hormone in the Anterior Pituitary Gland then travel to regulate the secretion of thyroid hormones in thyroid glands.
• Inhibiting Hormone is when a hormone prevents another release of Hormone.
• Blood levels of Hormones are determined by how they are secreted in pattern.
• Chronic Hormone Secretion is constant;stable blood levels of Hormone in long period of time which reaches days or weeks that are triggered by thyroid hormone.

  
• Acute Hormone Secretion is where hormone concentration changes suddenly and irregularly in short time; circulating levels differ in each stimulus.

  
• Episodic Hormonal Secretion are secreted in fair predictable intervals and concentration. Which is consistent time and to roughly the same amount. Example is reproductive Hormone that regulate menstruation that can last to days.

  
• Lipid-soluble Hormone is non polar.
• Water Soluble Hormone is Polar
• LSH or WSH

  
  

  LSH: Steroid Hormones are cholesterol based - testosterone,aldosterone.
• Amino acid derivative (in lipid-soluble)  

  Thyroid hormone (thyroxine)
• LSH or WSH

  
  

  LSH:Fatty acid derivatives Prostaglandins