Nervous System Anatomy and PhysiologyFunctions of the Nervous SystemTo carry out its normal role, the nervous system has three overlapping functions.1.Monitoring changes.Much like a sentry, it uses its millions of sensory receptors to monitor changesoccurring both inside and outside the body; these changes are called stimuli, and the gathered informationis called sensory input.2.Interpretation of sensory input.It processes and interprets the sensory input and decides what should bedone at each moment, a process calledintegration.3.Effects responses.It then effects a response by activating muscles or glands (effectors) via motor output.4.Mental activity.The brain is the center of mental activity, including consciousness, thinking, and memory.5.Homeostasis.This function depends on the ability of the nervous system to detect, interpret, and respondto changes in the internal and external conditions. It can help stimulate or inhibit the activities of othersystems to help maintain a constant internal environment.Anatomy of the Nervous SystemThe nervous system does not work alone to regulate and maintain body homeostasis; the endocrine system is asecond important regulating system.Organization of the Nervous System
We only have one nervous system, but, because of its complexity, it is difficult to consider all of its parts atthe same time; so, to simplify its study, we divide it in terms of its structures (structural classification) or in terms ofits activities (functional classification).Structural ClassificationThe structural classification, which includes all of the nervous system organs, has two subdivisions- the centralnervous system and the peripheral nervous system.●Central nervous system (CNS).The CNS consists of the brain and spinal cord, which occupy the dorsal bodycavity and act as the integrating and command centers of the nervous system●Peripheral nervous system (PNS).The PNS, the part of the nervous system outside the CNS, consists mainlyof the nerves that extend from the brain and spinal cord.Functional ClassificationThe functional classification scheme is concerned only with PNS structures.
●Sensory division. The sensory, or afferent division, consists of nerves (composed of nerve fibers) thatconvey impulses to the central nervous system from sensory receptors located in various parts of the body.●Somatic sensory fibers.Sensory fibers delivering impulses from the skin, skeletal muscles, and joints arecalled somatic sensory fibers.●Visceral sensory fibers.Those that transmit impulses from the visceral organs are called visceral sensoryfibers.●Motor division.The motor, orefferent divisioncarries impulses from the CNS to effector organs, themuscles and glands; the motor division has two subdivisions: thesomatic nervous systemandtheautonomic nervous system.