The parasympathetic nervous system
The parasympathetic nervous system is part of the autonomic system and is vital for bodily function. Unlike the voluntary nervous system which is consciously influenced to activate muscles and move joints, the parasympathetic nervous system is self regulated and not under our direct conscious control.
Role of the parasympathetic nervous system
The parasympathetic nervous system can be thought of as a system that controls many essential activities which require regulation, but which would require too much conscious effort to maintain. For example, it would be impossible to co-ordinate our heartbeat every second of the day or our digestive activities while we sleep. These activities are taken care of very effectively by the autonomic nervous system.
These activities do require control from our nervous system because they need to adapt to changing circumstances. For example, when we consume food, our digestive system needs to act to digest the food. When the food has been processed, the digestive system needs to reduce its activity otherwise it would end up digesting itself. Equally when we are active, digestion does not become so much of a priority, and our heart and sweat glands need to become more active. These complicated and essential activities need to be carried out without having to think.
The parasympathetic nervous system originates from the central nervous system via certain cranial nerves and spinal nerves. From here they branch off to various glands, the digestive system, the heart and many other internal organs. These nerves also carry sensory information back to the brain making the person aware of when their bladder is full, or when they need to defaecate. The parasympathetic nervous system is also responsible for the sensation of pain in many of our hollow organs. The parasympathetic nervous system is closely related to the enteric nervous system which moderates the digestive system. Other essential roles that it has includes the regulation of our core temperature and the production of tears, mucous and other important secretions.
Relation to the nervous system
The parasympathetic nervous system can be though of as acting to counterbalance the sympathetic nervous system enabling control over the viscera. Whereas the sympathetic nervous system covers a flight and fright response making the body ready for movement and activity, the parasympathetic system serves to ensure that the body is able to rest and digest. Without its influence, it would impossible to calm down, and we would be constantly in a state of arousal, in a cold sweat, and unable to process food efficiently. The parasympathetic and sympathetic nervous systems are constantly monitoring the internal environment and moderating their activity to promote a consistent equilibrium within our bodies.