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LIBIN LIFE
Maintaining balance Understanding autonomic dysfunction By Kate Bourne, PhD candidate
T
he autonomic nervous system is not something you normally think about in your everyday life. In contrast to the voluntary or somatic nervous system, which controls body movement, the autonomic nervous system works “automatically” to control the involuntary processes in your body including breathing rate, digestion, and your heart rate. The autonomic nervous system can be divided into two main components: the sympathetic nervous system, which is responsible for the body’s “fight or flight” response, and the parasympathetic nervous system, which can be thought of as the “rest and digest” system. When you are startled, for example, the sympathetic nervous system activates the “fight or flight” response by signaling the body to release more adrenaline, increasing your heart rate, breathing rate and perspiration. When you feel your heart pounding in your chest, it is the result of this system. The parasympathetic nervous system is responsible for processes when your
body is at rest, including digestion. A delicate balance of sympathetic and parasympathetic activity is required to maintain a state of balance in the body. If there is a disruption in the function of the sympathetic or parasympathetic nervous systems, this can lead to autonomic dysfunction. If you have ever fainted before, or felt lightheaded when standing up, you may have experienced a type of autonomic dysfunction. Syncope (fainting) and orthostatic intolerance are two common types of autonomic dysfunction, and ones that are studied at the Libin Cardiovascular Institute. Although there are many different causes of fainting, a type of syncope called neurocardiogenic or vasovagal syncope is caused by a sudden drop in heart rate and blood pressure, usually triggered by a stimulus such as prolonged standing, emotional distress or the sight of blood. Orthostatic intolerance occurs when the autonomic nervous system does not respond appropriately to standing. Patients with orthostatic intolerance have severe symptoms
when they stand up and may not be able to do so for long. Two common conditions of orthostatic intolerance are Postural Tachycardia Syndrome (POTS) and Orthostatic Hypotension (OH). Patients with POTS experience a rapid heart rate when standing, whereas patients with OH experience low blood pressure. Autonomic dysfunction is diagnosed using autonomic function testing, a series of specialized tests that evaluate the function of the sympathetic and parasympathetic nervous systems. Patients with autonomic dysfunction often experience quality of life impacts, and more research is required to try to understand underlying mechanisms and develop treatments for these disorders.
If you have ever fainted before, or felt lightheaded when standing up, you may have experienced a type of autonomic dysfunction.
