The body is a physical structure composed of the skeletal, muscular, endocrine, digestive, circulatory, respiratory, excretory, and the one I am representing, nervous, systems, yet the most priceless and vital one that surely should not be laid off is the nervous system. The nervous system consists of two sections. The first is the central nervous system (CNS). The CNS, which coordinates the activities of the entire nervous system, is composed of the brain (cerebrum, cerebellum, and medulla), and the spinal cord that is connected, via the brain stem, to the brain; nerve cells carry impulses from it. The CNS is responsible for sending sensory messages to all body parts. The cerebrum, in control of involuntary actions including memory, thought and senses, has two hemispheres; the right controls the left body and the left controls the right. The medulla, located at the brain stem, controls involuntary activities, such as breathing and heart rate. A person’s motor function and muscle coordination, balance, is associated with the cerebellum.
The second section is the peripheral nervous system (PNS).
The PNS, which can be further subdivided into the somatic and autonomic nervous systems, carries impulses to and from the CNS. It is made up of nerves outside of the Central Nervous System. The somatic is made up of voluntary muscles, sensory nerves and motor nerves; it makes muscles contract or relax, and processes sensory information including hearing, touch, and sight. The autonomic, responsible for controlling involuntary functions, and also connected with emotional responses, can be further broken down into the sympathetic nervous system, associated with the “fight or flight response,” where the body decides to either fight a danger or run from it, and the parasympathetic system that calms down the body. These two parts act on the body in opposite ways; this is known as antagonism. The sympathetic nervous system dilates pupils, inhibits the flow of saliva, accelerates heartbeat, dilates bronchi, inhibits peristalsis and secretion, converts glycogen to glucose, secretes adrenaline and noradrenaline, and inhibits bladder contraction. The parasympathetic system, which acts in opposition to the sympathetic nervous system, contracts pupils, stimulates the flow of saliva, slows heartbeat, constricts bronchi, stimulates peristalsis and secretion, stimulates the release of bile, and contracts the bladder. For example, the size of one’s pupils adjusts automatically, thus unconsciously, so that one might have optimal vision....