The Peripheral Nervous System
The peripheral nervous system consists of cranial nerves that control the structures of the head, and spinal nerves that control all other body functions. It is one of two components of the central nervous system and has two parts: the somatic nervous system and the autonomic nervous system.
The somatic nervous system is an information relaying structure. Twelve pairs of cranial nerves and thirty-one pairs of spinal nerves, contained in blood, lymph glands, internal and sense organs, and muscles, tendons and skin, carry sensory information to the brain and spinal cord. The somatic nervous system tells the brain what is happening both internally and externally, so it can prepare a suitable response.
The twelve cranial nerves control various important functions of the human body. These functions include both sensory and motor roles. Sensory functions are smell, vision, taste, hearing, and touch. The motor functions include cewing, eye movement, balance, and facial expression.
The autonomic nervous system, made up mostly of motor neurons, is responsible for controlling involuntary responses by sending out hormones and electrical impulses to the heart, lungs, stomach, intestines, liver, kidneys, sweat glands, salivary glands, and pupils of the eyes. It can slow down or speed up the body's organs and systems depending on the situation. The fight or flight reaction will be triggered if danger arises, and when the threat passes, the body will return to its normal resting state. The interaction of its two complimentary branches, the sympathetic nervous system, and the parasympathetic nervous system, keep the body balanced and working properly. But chronic stress can disturb this harmony, leading to anxiety related health problems.
The sympathetic nervous system readies the body to meet threatening or dangerous situations by revving up its defenses to meet the threat, and activating the fight or flight response. The parasympathetic nervous system activates the relaxation response when the all clear is sounded, renewing the body's resources while waiting for the next threat.