15 Chapter 15 The Autonomic Nervous System
By Krishnan Prabhakaran
Motivation
Abnormal functioning of the autonomic nervous system can be life threatening and there is a specific term for it: dysautonomia. Dysregulation of the autonomic nervous system can produce the apparent malfunction of the organs it regulates. For this reason, dysautonomia patients often present with numerous, seemingly unrelated maladies.
Symptoms are wide ranging and can include problems with the regulation of heart rate, blood pressure, body temperature and perspiration. Other symptoms include fatigue, lightheadedness, feeling faint or passing out (syncope), weakness and cognitive impairment.
Autonomic dysfunction can occur as a secondary condition of another disease process, like diabetes, or as a primary disorder where the autonomic nervous system is the only system impacted. These conditions are often misdiagnosed.
Over one million Americans are impacted with a primary autonomic system disorder. The more common forms of these conditions include Postural Orthostatic Tachycardia Syndrome POTS / Orthostatic Intolerance OI (Figure 15.1) , Neurocardiogenic Syncope NCS, Pure Autonomic Failure PAF and Multiple Systems Atrophy MSA.
Learning Objectives
Upon completion of the work in this chapter students should be able to:
- Compare and contrast the sympathetic and parasympathetic divisions of the nervous system
- Differentiate between the functions, target organs and neurotransmitters used by the sympathetic and parasympathetic divisions of the autonomic nervous system
Background.
The Autonomic Nervous System
The autonomic nervous system is tied into emotional responses and the fight-or-flight response sounds like a panic attack. In the modern world, these sorts of reactions are associated with anxiety as much as with response to a threat. It is engrained in the nervous system to respond like this. In fact, the adaptations of the autonomic nervous system probably predate the human species and are likely to be common to all mammals, and perhaps shared by many animals. However, the autonomic nervous system is not just about responding to threats. Besides the fight-or-flight response, there are the responses referred to as “rest and digest”. The digestive system has a big job to do. Much of the function of the autonomic system is based on the connections within an autonomic, or visceral, reflex.”
The Autonomic Nervous System at Work
Jayla is sitting, having an outdoor lunch with friends when a large spider lands on her plate. She immediately freezes, the food in her mouth begins to feel like a wad of dry hay, and she nearly gags as she tries to swallow it. She feels her heart race and pounding in her chest. After swallowing her food, it seems stuck in her throat and chest.
In this scenario, Jayla had been sitting, relaxed and enjoying a meal. In this relaxed state, the body would have a heart rate that is at rest, active peristalsis (activity in muscles of the digestive system),