A&PI Chapter 15

• Autonomic system


  Involuntary function that occurs 'without you actively telling your body to do it'
• Preganglionic Neuron

  • Cell body in CNS & axon extends to an autonomic ganglion
• Postganglionic Neuron

  • Unmyelinated axon extending from ganglion to effector (site of innervation)
• Sympathetic division


  • Cell bodies of preganglionic neurons: T1-L2/L3
• Parasympathetic division


  • Cell bodies of the preganglionic division: The nuclei of CN's III, VII, IX & X AND S2-S4 (Sacrum)
• Cranial Parasympathetic outflow

  Brain stem to the 4 CN's
• Sacral Parasympathetic outflow

  Extends from Sacral spinal N's 2-4
• Sympathetic Ganglia(& 2 Major Types)

  • Sympathetic trunk ganglia: lie in vertical row on either side of vertebral column
  • Prevertebral ganglia: lie anterior to vertebral column and close to large abdominal arteries
• Cholinergic Neurons

  • Release: Acetylcholine (Ach)
  • Include nicotinic receptors and muscarinic receptors
• Adrenergic neurons

  • Release: Norepinephrine (NE)
• Sympathetic

  • "fight-or-flight"/"go-into-action"/stress response
  • Therefore, think of what would happen to the body when you are in this state
  • Example: in intense stress/anxiety, heart rate would increase and body functions (digestion or urination) would decrease
• Parasympathetic

  • "rest and digest"/"just chillin" response
  • Functions like digestion, slowed heart rate, urination, etc. would occur
• Autonomic Tone


  • Balance between sympathetic & parasympathetic nervous system activity
  • Regulated by hypothalamus
  • When sympathetic input increases, parasympathetic input decreases (& vice versa)