Sympathetic Nervous System


Sympathetic Nervous System, Sympathetic System, Sympathetic Nerve

  • Definitions
  1. Sympathetic Nervous System
    1. Part of Autonomic Nervous System with activity that typically counters the Parasympathetic Nervous System
    2. Energy expending (catabolic) system, activated in stressful situations (e.g. emergency fight or flight)
      1. Contrast with the Parasympathetic Nervous System, an energy conserving system activated at times of rest
  • Physiology
  • Activity
  1. See Adrenergic Receptor
  2. See Alpha Adrenergic Receptor (alpha 1 and alpha 2)
  3. See Beta Adrenergic Receptor (beta 1 and beta 2)
  4. Increases Heart Rate (chronotropic), heart contraction strength (ionotropic), Blood Pressure
  5. Increases Respiratory Rate and bronchodilation
  6. Increases pupil size or Mydriasis (contrast with Miosis and accommodation by the Parasympathetic System)
  7. Stimulates Salivary VISCOUS secretion (contrast with watery secretion by Parasympathetic System)
  8. Stimulates sweat secretion (via Cholinergic postganglionic fibers)
  9. Decreases gastrointestinal activity and secretion, and contracts gastrointestinal sphincters
  10. Stimulates liver Gluconeogenesis and glycogenesis and fat lipolysis
  11. Stimulates Kidney renin release and Adrenal MedullaEpinephrine release (Cholinergic postganglionic fibers)
  12. Mediates ejaculation (contrast with Erection mediated by Parasympathetic System)
  13. Shunts Blood Flow to critical organs
    1. Cardiac Muscle and skeletal Muscle vasodilation (beta-2 receptor)
    2. Skin and gastrointestinal Vasoconstriction (alpha-1 receptor)
  • Anatomy
  1. Thoracolumbar division of the Autonomic Nervous System
  2. Signals originate in the spinal cord intermediolateral column (T1 to L2)
  3. Transmit to target organs via paravertebral or prevertebral ganglia
  4. Images
    1. sympatheticNervousSystem.jpg
  • Pathophysiology
  • References
  1. Goldberg (2014) Clinical Neuroanatomy, Medmaster, p. 54-60
  2. Netter (1997) Atlas Human Anatomy, ICON Learning, p. 152-4