Describe the organization of the nervous system, including a description of the

The entire nervous system is organized into two main divisions: the central nervous system and the peripheral nervous system. The central nervous system (the brain and spinal cord) receives sensory input from the body, which it integrates to determine whether a response is warranted. Within the central nervous system, learning, memory, emotion, and other complex functions occur. The peripheral nervous system is divided into two main divisions: the afferent and efferent limbs. The afferent limb detects sensory (external) and visceral (internal) information and sends it to the central nervous system. The efferent limb sends information to the effector organ from the central nervous system to initiate a response. The efferent limb can be divided into two branches: the autonomic nervous system and the somatic nervous system. The somatic nervous system transmits information to skeletal muscle, whereas the autonomic nervous system sends information either through the sympathetic or parasympathetic nervous systems, which tend to be counterregulatory (produce the opposite effects). The autonomic nervous system is not under voluntary control. Finally, there is the enteric nervous system in the gastrointestinal tract, involved in digestion, that acts independently of the central and peripheral nervous systems.