The Autonomic Nervous System (ANS) acts through a balance of its two components, the sympathetic nervous system and parasympathetic nervous system.
The ANS is predominantly an efferent system transmitting impulses from the Central Nervous System (CNS) to peripheral organ systems.

Its EFFECTS include:

• Control of heart rate and force of contraction
• Constriction and dilatation of blood vessels
• Coordination of body temperature, respiration, digestion and other vital functions
• Contraction and relaxation of smooth muscle in various organs
• Visual accommodation
• Pupillary size and secretions from exocrine and endocrine glands
  
  Autonomic Failure / Dysautonomia
  This refers to the malfunctioning of Autonomic Nervous System or Dysautonomia which results from dysregulation between the sympathetic and parasympathetic sections.

SIGNS

• Drop in BP while sitting or standing (orthostatic hypotension)
• Drop in BP shortly after meal (postprandial hypotension)
  These drop hinders adequate blood flow to the brain portion, thus leading to dizziness and unconsciousness.

TYPES

• Adie Syndrome
• Autonomic Dysreflexia 
• Autonomic Neuropathy
• Complex Regional Pain Syndromes
• Dysautonomia (Autonomic Dysfunction)
• Familial Dysautonomia
• Gustatory Sweating
•  Horner's Syndrome
• Multiple System Atrophy with Orthostatic Hypotension
• Neurocardiogenic Syncope (NCS)
• Orthostatic Hypotension
• Postural Orthostatic Tachycardia Syndrome (POTS)
• Shy-Drager Syndrome

DIAGNOSIS

• History of family
• Detailed physical exam

TREATMENT

• Applying external pressure to the lower half of the body; Custom-fitted counterpressure support garments can be used
• Physical maneuvers / exercises
• Fludrocortisone - drug for retaining water and controlling blood pressure