Author Linda Kohanov in her book The Tao of Equus (2001), provides an excellent description of the Autonomic Nervous System as it relates to both the “flight or fight”, and the “rest and digest” functions that living beings experience during stressful situations:

Courtesy of Radcliffe Cardiology

Sympathetic Nervous System

Kohanov states that the following bodily functions occur in support of the “flight or fight” response (to a perceived threat) when nerve impulses are transmitted from the deep brain outward to the organs and tissues (2001):

  • Skin sweats
  • Eyes dilate
  • Increased heart rate and blood pressure
  • The digestive system slows and diverts blood to the vital organs (heart, lungs, and brain)
  • The hormones adrenaline and cortisol are released into the bloodstream and cause the following additional symptoms of stress: shaking, pale skin, shallow breathing, nausea, light-headedness

Parasympathetic Nervous System

Kohanov further related that the “rest and digest” functions kick in when a perceived threat to our being has passed, and a being will experience the following:

  • Decreased heart rate and blood pressure
  • Constricted pupils
  • Increased gastric secretions
  • Return to a state of equilibrium (balance)

Enteric Nervous System

Courtesy of Psychology Today

Kohanov tells us that the Enteric Nervous System works in relation with the Sympathetic through a network of nerves that surround the Digestive System (2001). When a perceived threat occurs, the Enteric system prepares for a potential injury in the following manner:

  • Release of histamines that initiate the inflammatory response in the small intestine
  • Immune cells are attracted to this area of the body in anticipation of some type of physical trauma.

To illustrate this phenomenon, Kohanov gave the following scenario:

Our small intestine is full of bacteria (both good and bad), and if the abdominal area was pierced by a knife or other sharp object, said bacteria would be released into the bloodstream, and potentially cause a systemic infection. However, since the enteric system activates prior to injury, the small intestine is armed with immune cells that can thwart foreign invaders and increase one’s chances for survival (2001).

All above described physical reactions are experienced by mammals of both the human and animal kingdoms, and are designed to assist us during acute, life-threatening situations.

What happens when all situations are not life-threats and the stress response becomes chronic? This is a discussion for another day. Until next time-

Be well and take care,



Kohanov, L. (2001). The Tao of Equus: A Woman’s Journey of Healing & Transformation through the Way of the Horse. California: New World Library.