The autonomic nervous system (ANS) is the system that controls the majority of involuntary or ‘automatic functions of the body. The autonomic nervous system regulates the body’s responses without consciously thinking such as breathing, heart rate, blood pressure, digestion, sexual arousal & many other biochemical processes. The autonomic nervous system sends signals through nerves pathways to control & regulate most organ function such as the heart, lungs, kidney’s etc. The autonomic nervous system is a very complex system of nerves starting in the brain and sent via the spinal cord through peripheral nerves that extend to all parts of the body.
The autonomic nervous system is located in three main areas of the body. The central part of the autonomic nervous system is located in the brain in areas known as the medulla oblogata and in the lower brain stem known as the hypothalmus. The other two portions of the autonomic nervous system (sympathetic nervous system branch & parasympathetic nervous system branch) are found in the peripheral nerves.
The medulla oblongata is the part of the brain that regulates cardiac, respiratory, vasomotor control, as well as reflexes like coughing, sneezing, vommitting and swallowing. The hypothalmus, another part of the brain, performs a supporting role by linking the nervous system to the endocrine system. The hypothalmus regulates body temperature, thirst, hunger, sleep and circadian rythyms in the body. Through endocrine control, the hypothamlus also plays a role in regulating blood volume and blood pressure.
There are two distinct divisions of the autonomic nervous system. These branches are known as the sympathetic nervous system and the parasympathetic nervous system.
The Sympathetic Nervous System is commonly associated with the “fight or flight” responses – those bodily reactions that you need to respond quickly in an emergency. When faced with a life threatening situation, your human instinct takes over and you either fight the danger you are facing, or you take flight and run away from the danger. Your Sympathetic Nervous System allows your body to do this rapidly. For example, in the face of danger, your Sympathetic Nervous system will cause bronchial dilation – this allows you to breathe better while you are fighting or running away from the dangerous situation. Likewise, your heart will beat stronger and faster, also prepping the body to fight or take flight.
The Parasympathetic Nervous System is commonly associated with the “rest and digest” responses – those bodily actions needed to restore energy and rest the body. For example, chewing food triggers the Parasympathetic Nervous System to increase production of saliva and to increase digestion in the gut. The Parasympathetic Nervous System also increases gallbladder function, which assists in the digestive process.