The Nervous System
The nervous system has 3 main functions: sensory, integration, and motor.
Sensory The Nervous System's sensory function involves collecting information from things called sensory receptors that monitor the body’s internal and external conditions. Those signals will then be passed on to the central nervous system (CNS) for further processing by things called afferent neurons (and nerves too).
Integration The integration process is the processing of the many sensory signals that are passed into the CNS at any given time (Explained Above). These signals are evaluated, compared, used for decision making, discarded or committed to memory as the Nervous System thinks would be appropriate. Integration takes place in the gray matter of the brain and spinal cord and is performed by interneurons. Many of them work together to form complex "networks" that provide this processing power.
Motor Once the networks of interneurons in the CNS evaluate sensory information and decide on an action (Also explained above), they stimulate efferent neurons. Efferent neurons (AKA motor neurons) carry signals from the gray matter, of the CNS, in the Brain, through the nerves of the peripheral nervous system (PNS) to effector cells. The effector may be smooth, cardiac, or skeletal muscle tissue or glandular tissue. The effector then releases a hormone or moves a part of the body to respond to the stimulus (Endocrine System).
The Organs and Their Functions
The importance of the Nervous System to the body's function is that it allows us to respond to our internal and external environment, maintain our internal stability, and also coordinates our behavior, it even allows other body systems to function, which would probably make it the most important in my opinion. Basically without the nervous system we wouldn't be able to do anything and our species would go extinct due to us dying and being unable to perform bodily functions.
Its Importance to the Body's Function
The nervous system made up of the brain, spinal cord, sensory organs, and all of the nerves that connect these organs with the rest of the body.
Brain The brain is a soft, wrinkled organ that weighs about 3 pounds, and is located inside the cranial cavity, where the bones of the skull can surround and protect it. The approximately 100 billion neurons of the brain form the main control center of the body. The brain and spinal cord together can form the central nervous system (CNS), where information is processed and responses come from. The brain can control higher mental functions such as consciousness, memory, planning, and voluntary actions, and can also control lower body functions like the maintenance of respiration, heart rate, blood pressure, and digestion.
Spinal Cord The spinal cord is a long, thin thing of bundled neurons that carries information through the vertebral cavity of the spine beginning at the medulla oblongata of the brain on its superior end and continuing inferiorly to the lumbar region of the spine. In the lumbar region, the spinal cord separates into a bundle of individual nerves called the cauda equina (due to its resemblance to a horse’s tail) that continues inferiorly to the sacrum and coccyx. The white matter of the spinal cord functions as the main conduit of nerve signals to the body from the brain. The grey matter of the spinal cord integrates reflexes to stimuli. In other words, It carries info from the brain, down the spine, and to the body and nerves.
Nerves Nerves are bundles of axons in the peripheral nervous system (PNS) that act as information highways to carry signals between the brain and spinal cord and the rest of the body (Kinda like the Spinal Cord). Each axon is wrapped in a connective tissue sheath called the endoneurium. Individual axons of the nerve are bundled into groups of axons called fascicles, wrapped in a sheath of connective tissue called the perineurium. Finally, many fascicles are wrapped together in another layer of connective tissue called the epineurium to form a whole nerve. The wrapping of nerves with connective tissue helps to protect the axons and to increase the speed of their communication within the body. In other words, it is the road for info to carry signals between the brain and spinal cord and the body to cause actions.
Afferent, Efferent, and Mixed Nerves. Some of the nerves in the body are specialized for carrying information in only one direction, which is kind of like to a one-way street. Nerves that carry information from sensory receptors to the central nervous system only are called afferent nerves. Other neurons, known as efferent nerves, carry signals only from the central nervous system to effectors such as muscles and glands. Finally, some nerves are mixed nerves that contain both afferent and efferent axons. Mixed nerves function like 2-way streets where afferent axons act as lanes heading toward the central nervous system and efferent axons act as lanes heading away from the central nervous system.
Cranial Nerves. Extending from the inferior side of the brain are 12 pairs of cranial nerves. Each cranial nerve pair is identified by a Roman numeral 1 to 12 (I II III IV V VI VII VIII IX X XI XII) based upon its location along the anterior-posterior axis of the brain. Each nerve also has a descriptive name (like the: olfactory, optic, etc.) that identifies its function or location. The cranial nerves provide a direct connection to the brain for the special sense organs, muscles of the head, neck, and shoulders, the heart, and the GI tract.
Spinal Nerves. Extending from the left and right sides of the spinal cord are 31 pairs of spinal nerves. The spinal nerves are mixed nerves that carry both sensory and motor signals between the spinal cord and specific regions of the body. The 31 spinal nerves are split into 5 groups named for the 5 regions of the vertebral column. Thus, there are 8 pairs of cervical nerves, 12 pairs of thoracic nerves, 5 pairs of lumbar nerves, 5 pairs of sacral nerves, and 1 pair of coccygeal nerves. Each spinal nerve exits from the spinal cord through the intervertebral foramen between a pair of vertebrae or between the C1 vertebra and the occipital bone of the skull.
Sense Organs All of the bodies’ many sense organs are components of the nervous system. What are known as the special senses—vision, taste, smell, hearing, and balance—are all detected by specialized organs such as the eyes, taste buds, and olfactory epithelium. Sensory receptors for the general senses like touch, temperature, and pain are found throughout most of the body. All of the sensory receptors of the body are connected to afferent neurons that carry their sensory information to the CNS to be processed and integrated.
Finley, Mary. "Nervous system." The Gale Encyclopedia of Science. Ed. K. Lee Lerner and Brenda Wilmoth Lerner. 5th ed. Farmington Hills, MI: Gale, 2014. Student Resources in Context. Web. 18 Nov. 2014.