General properties of the Sympathetic Nervous System.

• Mediates the body's response to activity, stress, danger, or environmental challenge.
  The overall pattern of sympathetic activation is typified by the fright, fight or flight
  reaction to danger. Its responses include:
  
  • Increased Heart Rate and Contractility.
  • Dilation of bronchioles for easier breathing.
  • Constriction of arterioles in skin, digestive system, and non-exercising muscles.
  • Inhibition of digestive functions.
  • Widening of pupils.
  • Increased glucose in blood due to glycogenolysis in liver.
  • Increased fatty acid in blood from adipose tissues.
  • Piloerection.
  • Cold sweat (stimulated sweating with constricted skin arterioles).
    
• Involved in expending energy.
• Originates in the thoracic and lumbar spinal cord.
• Intermediate synapses near spinal cord, far from target organ. Most of the synapses are in the
  paravertebral ganglia near the spinal cord. Preganglionic fibers are short, postganglionic are long.
• Sympathetic neurons branch extensively. One cell may innervate many target cells, leading to
  more generalized sympathetic responses in the body.
• The Sympathetic system can also act selectively in some reflexes.
• Primary target tissues are:
  
  • Cardiovascular system.
  • Lungs.
  • Smooth muscle in all organs.
  • Some glands (sweat, salivary, and digestive).
  • Metabolic tissue (fat cells, liver).
    
• Sympathetic stimulation can cause excitation of some tissues, inhibition of others.
  For example, contraction of arteriolar smooth muscle and relaxation of bronchiolar
  smooth muscle are both due to sympathetic stimulation.