Did you know that there are more nerve cells in the human brain than there are stars in the Milky Way? The nervous system is one of the most important systems in the human body. Without the nervous system, no other system could function in the body. Our nervous system helps us feel pain, move, and also tells other systems in the body what to do. The nervous system is the network of cells and nerve fibers that transmit nerve impulses throughout the body. It consists of two main parts, the central nervous system, or CNS, and the peripheral nervous system, or PNS. The central nervous system is made up of the spinal cord and the brain. The job of the CNS is to receive information from different parts of the body, analyze and store it, and then send instructions based on the information received. The peripheral nervous system is composed mainly of nerves and neurons. The PNS connects the central nervous system to the limbs and organs of the body. However, unlike the central nervous system, the peripheral nervous system is not protected by bone or the blood-brain barrier, making it easier to be exposed to toxins and injury. The central nervous system contains the brain, which is the control center. of the body. In the brain, there are three main constituents: the forebrain, the brainstem and the hindbrain. The forebrain receives and processes sensory information and controls motor function. The thalamus and hypothalamus are responsible for motor control, transmission of sensory information, and control of autonomic functions. The forebrain also contains the cerebrum, the largest part of the brain. The majority of information processing in the brain takes place in the cerebral cortex. The brains......middle of paper......together very simply. Sensory nerve fibers react to different things and produce chemical responses. These chemical responses determine how sensations interact. Once these sensations are interpreted, an impulse travels through the nerve to the spinal cord and reaches the brain, all within fractions of a second. Once the brain receives the message, it sends it back through the spine and to the nerves. Sometimes it is not necessary for a signal to reach the brain before a decision is made. These occur in the dorsal horn, which is a section of the spine that serves as an information center. When the dorsal horn makes a decision before the brain, we speak of “reflexes”. However, once the dorsal horn sends a signal, the original information continues to travel to the brain so that it can be stored and processed to a greater extent...