Did you know that there are more nerve cells in the human brain than stars in the Milky Way? The nervous system is one of the most important systems of the human body. Without the nervous system no other system would be able to function in the body. Our nervous system helps us relieve pain, move, and also tells other systems in the body what to do. The nervous system is the network of nerve cells and 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 consists of the spinal cord and the brain. The central nervous system's job is to receive information from various parts of the body, analyze and store the information, and then send instructions based on the information received. The peripheral nervous system is mainly composed 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 bones or the blood-brain barrier, making it easy to expose to toxins and injury. The central nervous system contains the brain, which is the control center. of the body. There are three main constituents of the brain: 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. Most information processing in the brain occurs in the cerebral cortex. The brain... in the center of the card... together in a very simple way. Sensory nerve fibers respond 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 in fractions of a second. Once the brain receives the message, it sends it back through the spine and to the nerves. Sometimes, a signal does not need to reach the brain before a decision is made. These occur in the dorsal horn, which is a section of the spinal column that serves as an information center. When the dorsal horn makes a decision before the brain, these are called “reflexes”. However, once the dorsal horn sends a signal, the original information still travels to the brain so that it can be stored and processed to a greater extent..