Sympathetic Nervous System

The sympathetic nervous system is a part of the peripheral nervous system. To understand the sympathetic nervous system definition, one needs to first understand the different parts of the nervous system. The nervous system is divided into the central nervous system and the peripheral nervous system. The autonomic nervous system is a part of the peripheral nervous system that is involved in controlling the functioning of the body below the level of consciousness. The autonomic nervous system is further divided into three parts - the enteric system, the sympathetic system and the parasympathetic system. Given below are details regarding the sympathetic nervous system functions, structure, disorders and what happens when this system is activated.

Structure
Sympathetic nerves originate in the vertebral column beginning in the first thoracic segment of the spinal cord, extending till the second or third lumbar segments. In order to reach the various target organs, the axons of the nerves travel long distances in the body. Information travels through the sympathetic system in a bidirectional flow, that is, the messages can trigger different changes in the body simultaneously. This is important, because the main function of the sympathetic system is to bring about instant changes in the body which readies it for facing a stressful situation.

Function
The sympathetic system is responsible for mobilizing the body's responses under stressful situations. It is the system that is supposed to initialize the 'flight or fight' response of the body. This is the part of the nervous system that is responsible for mediating the neuronal and hormonal stress response. It acts on many different organs of the body:

• It acts on the eyes by increasing the diameter of the pupil by dilation.
• It acts on the heart to increase the heart rate by increasing the force of contraction of the heart muscles. The sympathetic nervous system and blood pressure are also directly related, as an increase in the heart rate and force of contraction eventually leads to a rise in blood pressure.
• It acts on the lungs by causing dilation of the bronchioles so as to increase the airway passage available.
• It acts on the digestive system by preventing and inhibiting the movement of food.
• It acts on the kidney to increase the secretion of renin.
• It acts on the penis to promote ejaculation.

Thus, the sympathetic nervous system response is such that it equips the body to handle a situation of stress. It primarily activates large amounts of secretion of adrenaline from the adrenal glands. It is also active at a basal level so as to maintain a state of homeostasis in the body.

Disorders
There are many diseases that can affect the functioning of the sympathetic system. These conditions tend to slowly cause degeneration of the nerves, thus, affecting their transmission system. One of the long term effects of alcohol includes degeneration of the peripheral nervous system. Initial consumption of alcohol causes alcoholic cardiomyopathy, which is said to occur due to an increase in the sympathetic output. One of the diseases that affects the central and autonomic nervous system is Parkinson's disease. In this disease, besides impairment of motor skills, there is also alteration in the functioning of the autonomic system, leading to secondary symptoms like orthostatic hypotension, oily skin, excessive sweating, urinary incontinence, altered sexual function, etc.

The sympathetic nervous system is an important component of the nervous system and plays a vital role in stressful situations. Hope this article was interesting and informative!