Peripheral+Nervous+System

__References__ http://www.sciencedaily.com/articles/p/peripheral_nervous_system.htm

http://biology.about.com/od/organsystems/a/aa061804a.htm

http://www.medicalook.com/human_anatomy/systems/Peripheral_nervous_system.html



The Peripheral Nervous System works with the Central Nervous system and is very dependent upon it. The peripheral nervous system communicates between the central nervous system and the body. It transmits information by pulsations to and from the brain and spinal cord. It consists of nerve tissues outside of the central nervous system. There are two types of nerves, cranial and spinal. The cranial nerves are from the brain and the spinal nerves are from the spinal cord. The central nervous system is unable to send information to the body without the peripheral nervous system. The peripheral nervous system is not protected by bone or the blood brain barrier, so it can be exposed to toxins. The sensory nervous system is the pulse leaving the sense that is sending the information toward the spinal cord constructed of neurons that convey special pulsations to the central nervous system. It sends information to the central nervous system from organs. The motor nervous system is the opposite of the sensory nervous system, it carries information from the central nervous to organs, muscles, and glands. There are four sections of the peripheral nervous system. The first is the somatic nervous system, it controls skeletal muscle, external sensory organs such as skin. It is voluntary because the responses are controlled consciously. Reflex reactions are an exception because they are involuntary reactions to external stimuli. The second is the autonomic nervous system, it controls involuntary muscles, smooth cardiac. It is also called the involuntary nervous system. The third is the sympathetic nervous system, it controls activities that increase energy. It controls functions such as speeding up the heart rate, dilating pupils, and relaxing the bladder. The fourth is the parasympathetic, it controls activities that conserve energy. It controls functions such as slowing down the heart rate, constricting pupils, and contracting the bladder.