Peripheral nervous system - Wikipedia
CNS vs PNS. CNS is the Central Nervous System that functions in order to coordinate each and every activity taking place in all the parts of the. This makes the brain to body ratio of the human times greater than that of the the peripheral nervous system (PNS) and the central nervous system (CNS). The main aim of this article is to communicate the differences between central nervous system (CNS) and Peripheral nervous system (PNS). Peripheral nervous system (PNS) is comprised of cranial nerves that are arising from the brain and the spinal nerves that are arising from the.
One unique cranial nerve is the vagus nervewhich receives sensory information from organs in the thorax and abdomen. The accessory nerve is responsible for innervating the sternocleidomastoid and trapezius musclesneither of which being exclusively in the head. For the rest of the body, spinal nerves are responsible for somatosensory information.
Peripheral nervous system
These arise from the spinal cord. Usually these arise as a web "plexus" of interconnected nerves roots that arrange to form single nerves. These nerves control the functions of the rest of the body. In humans, there are 31 pairs of spinal nerves: These nerve roots are named according to the spinal vertebrata which they are adjacent to.
In the cervical region, the spinal nerve roots come out above the corresponding vertebrae i.
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From the thoracic region to the coccygeal region, the spinal nerve roots come out below the corresponding vertebrae. It is important to note that this method creates a problem when naming the spinal nerve root between C7 and T1 so it is called spinal nerve root C8. In the lumbar and sacral region, the spinal nerve roots travel within the dural sac and they travel below the level of L2 as the cauda equina. Cervical spinal nerves C1—C4 [ edit ] Further information: Cervical plexus The first 4 cervical spinal nerves, C1 through C4, split and recombine to produce a variety of nerves that serve the neck and back of head.
Spinal nerve C1 is called the suboccipital nervewhich provides motor innervation to muscles at the base of the skull. C2 and C3 form many of the nerves of the neck, providing both sensory and motor control. These include the greater occipital nervewhich provides sensation to the back of the head, the lesser occipital nervewhich provides sensation to the area behind the earsthe greater auricular nerve and the lesser auricular nerve. Upon CNS injury astrocytes will proliferate, causing gliosisa form of neuronal scar tissue, lacking in functional neurons.
Apart from cortical gray matter there is also subcortical gray matter making up a large number of different nuclei. Spinal cord Diagram of the columns and of the course of the fibers in the spinal cord.
Sensory synapses occur in the dorsal spinal cord above in this imageand motor nerves leave through the ventral as well as lateral horns of the spinal cord as seen below in the image. Different ways in which the central nervous system can be activated without engaging the cortex, and making us aware of the actions. The above example shows the process in which the pupil dilates during dim light, activating neurons in the spinal cord.
The second example shows the constriction of the pupil as a result of the activation of the Eddinger-Westphal nucleus a cerebral ganglion. From and to the spinal cord are projections of the peripheral nervous system in the form of spinal nerves sometimes segmental nerves . The nerves connect the spinal cord to skin, joints, muscles etc. All in all 31 spinal nerves project from the brain stem,  some forming plexa as they branch out, such as the brachial plexasacral plexa etc.
Schematic image showing the locations of a few tracts of the spinal cord. Reflexes may also occur without engaging more than one neuron of the central nervous system as in the below example of a short reflex.
Cranial nerves[ edit ] Apart from the spinal cord, there are also peripheral nerves of the PNS that synapse through intermediaries or ganglia directly on the CNS. These 12 nerves exist in the head and neck region and are called cranial nerves. Cranial nerves bring information to the CNS to and from the face, as well as to certain muscles such as the trapezius musclewhich is innervated by accessory nerves  as well as certain cervical spinal nerves.
This is because they do not synapse first on peripheral ganglia, but directly on central nervous neurons. The olfactory epithelium is significant in that it consists of central nervous tissue expressed in direct contact to the environment, allowing for administration of certain pharmaceuticals and drugs.
Difference Between CNS and PNS | Difference Between | CNS vs PNS
Brain Rostrally to the spinal cord lies the brain. The brain is the major functional unit of the central nervous system. While the spinal cord has certain processing ability such as that of spinal locomotion and can process reflexesthe brain is the major processing unit of the nervous system.
Brainstem The brainstem consists of the medullathe pons and the midbrain. The medulla can be referred to as an extension of the spinal cord, and its organization and functional properties are similar to those of the spinal cord. Other nuclei are involved in balancetastehearing and control of muscles of the face and neck. Nuclei in the pons include pontine nuclei which work with the cerebellum and transmit information between the cerebellum and the cerebral cortex.
Additionally parts of the visual and auditory systems are located in the mid brain, including control of automatic eye movements. Such functions may engage the heartblood vesselspupillaeamong others. Cerebellum The cerebellum lies behind the pons. The cerebellum is composed of several dividing fissures and lobes.
Difference Between Central and Peripheral Nervous System | Definition, Components, Function
Its function includes the control of posture, and the coordination of movements of parts of the body, including the eyes and head as well as the limbs. Further it is involved in motion that has been learned and perfected though practice, and will adapt to new learned movements.
DiencephalonThalamusand Hypothalamus The two structures of the diencephalon worth noting are the thalamus and the hypothalamus. The thalamus acts as a linkage between incoming pathways from the peripheral nervous system as well as the optical nerve though it does not receive input from the olfactory nerve to the cerebral hemispheres.
Previously it was considered only a "relay station", but it is engaged in the sorting of information that will reach cerebral hemispheres neocortex. In common with the aforementioned reticular system the thalamus is involved in wakefullness and consciousness, such as though the SCN.
This is regulated partly through control of secretion of hormones from the pituitary gland. Additionally the hypothalamus plays a role in motivation and many other behaviors of the individual.