The peripheral nervous system comprises of all nerves located outside the brain and the spinal cord. The system comprises of sense organs that are used to detect stimuli from inside and outside the body. There are also some special sense organs that detect particular stimuli. The general types of senses include touch, vibration, pain, pressure and temperature. The peripheral nervous system has a number of neurons that have myelinated and unmyelinated axons. The sensory or afferent nerves which are part of the peripheral nervous system are linked to sensory organs and sensors in the skin, internal organs as well as the muscle.
They do interaction with the outside world and receive conscious information from the senses. This forms the sensory somatic nervous system comprises of 12 cranial nerves pairs and spinal nerves consisting of 31 pairs (Henry, 2001, p. 11). The nervous system comprises of the spinal cord and the brain which forms the central nervous system and the nerves branching off the brain and spinal cord (the peripheral nervous system). Most of the brain and spiral cord as well as most peripheral nerves perform to get messages from the external environment (stimuli) and subsequently respond to the stimuli.
This nervous system part is sometimes referred to as the voluntary system. Different stimuli from the outside environment are perceived by a system of several dendrites. This system comprises of a small process that extends from the soma. They come in bigger numbers than just one per cell. The dendrites work is to carry messages (nerve impulses) toward the soma and have several types of specialized receptors at their final portion. Axon, which happens to be one for every neuron, carries the nerve impulse far away from the soma, to the organs of effecter.
The axon end contain vesicles that release neurotransmitters, which are basically, substances that stimulate the effecter organ to function properly. The axons are generally white because of the lipid substance, myelin, which covers the axon. Myelin functions to insulate the axon as well as allowing the nerve impulse to move at super sonic speed (268 miles per hour). Other cells such as neuralgia cells function as auxiliary cells to the nervous system. The neuroglia cells which include the Schwann cell, forms the myelin sheath around axons and the astrocyte that forms the barrier of the blood brain (Henry, 2001, p. 35).
The Neurons ferries messages to the brain and the spinal cord through nerve impulses which are a form of electrical energy set in motion by stimulus. The real impulse of the nerve is due to sodium ions which have strong positive charge. They flow into the nerve fibers and displace the weaker potassium ions leading to slight negative charge on the outer part of the neuron, a process usually referred to as depolarization. The cascading impact of the sodium ions into the nerve fiber leads to change of the out side fiber to a negative charge for a millisecond.
Meanwhile the electrical energy goes down the fiber (Henry, 2001, p. 45). The electrical energy which contains the messages is relayed by the spinal cord to and from the brain through the nerves which comprises of bundles of several nerve cells. The brain’s sensory center integrates the barrage of input and subsequently generates a response. References Henry, W. (2001) The fine structure of the nervous system; Neurons and their supporting cells. Oxford: Oxford University Press.