17.4 Relationship of Sympathetic/Parasympathetic Division

• • Most organs innervated by autonomic nervous system are innervated by both the sympathetic and parasympathetic branches. Typically one division will increase activity of the organ, and the other will decrease the organ’s activity.
• Sympathetic division has widespread impact reaching visceral organs and tissues throughout body
• Parasympathetic division modifies activity of structures innervated by some cranial/pelvic nerves
• Most vital organs receive dual innervation
• Dual innervation is innervated by both sympathetic and parasympathetic divisions
• Where dual innervation exists, two divisions often have opposite or antagonist effects 
• Anatomy of Dual Innervation. In head.

  • Sympathetic postganglionic fibers from ciliary, pterygopalatine, submandibular, and otic ganglia accompany cranial nerves to peripheral destinations 
  • Sympathetic innervation reaches same structures above by traveling directly from superior cervical ganglia of sympathetic chain
• Anatomy of Dual Innervation. In thoracic and abdominopelvic cavities

  • Sympathetic postganglionic fibers intermix with parasympathetic preganglionic fibers at series of plexuses 
  • Cardiac plexus, pulmonary plexus, esophageal plexus, celiac plexus, inferior mesenteric plexus, hypogastric plexus 
  • Nerves leaving plexus above travel with blood vessels and lymphatics supplying visceral organs
• Autonomic fibers entering thoracic cavity intersect at cardiac plexus and pulmonary plexus
• Plexuses contain sympathetic fibers innervating heart and parasympathetic fibers innervating heart and lungs
• Esophageal plexus contains descending branches of vagus nerve and splanchnic nerves leaving sympathetic chain ganglia on each side
• Parasympathetic preganglionic fibers of vagus nerve follow esophagus as it enters abdominopelvic cavity
• Parasympathetic fibers joining network of celiac plexus
• Celiac plexus and associated smaller plexus, inferior mesenteric plexus, innervate viscera within abdominal cavity
• Hypogastric plexus contains parasympathetic outflow of pelvic nerves, sympathetic postganglionic fibers from inferior mesenteric ganglion, and sacral splanchnic nerves from sympathetic chain
• Visceral Reflex. Visceral reflexes are autonomic reflexes initiated in the viscera
• Visceral Reflex. Provide automatic motor responses modified by higher centers, especially of hypothalamus
• Visceral Reflex. All visceral reflexes are polysynaptic
• Visceral Reflex. Each visceral reflex arc is made up of a receptor, a sensory nerve, a processing center in the CNS and two visceral motor neurons (preganglionic and ganglionic) 
• Visceral Reflex. Afferent (sensory) nerves deliver info to CNS along spinal/cranial/autonomic nerves innervating peripheral effectors
• Visceral Reflex. Visceral reflexes either long or short
• Visceral Reflex.

  • Long reflexes of ANS resemble polysynaptic reflexes 
  • Short reflexes bypass CNS entirely
• What are visceral reflexes?

  Visceral reflexes are the simplest functional units in the autonomic nervous system. They provide automatic motor responses that can be modified, facilitated, or inhibited by higher centers, especially those of the hypothalamus.
• Name three plexuses in the abdominopelvic cavity.

  The celiac plexus, the inferior mesenteric plexus, and the hypogastric plexus are three plexuses in the abdominopelvic cavity.