Difference Between CNS and PNS (With Table)

The human body is the most complicated thing that has to be understood to know how and when a reaction in the body takes place. The nervous system is an important part of the body as it is responsible for its normal working. There are several types of the nervous system in the body, and collectively they perform some functions such as, the nervous system sends messages to the body to control the internal bodily environment, it is responsible for reflexing of spinal cords, they also perform roles in memorizing and learning things, they are responsible for all of the voluntary movements, etc.

The two main nervous systems are CNS and PNS that carry out most of the body functions.

CNS vs PNS

The difference between CNS and PNS is that both of them are responsible for different bodily functions. CNS majorly is responsible for organizing and analyzing messages or information received from different sensory organs and all of the voluntary functions, whereas PNS majorly is responsible for carrying out information to the CNS and conveying motor impulses to different organs. Damage to any nerve of the CNS will cause a major and global effect on the body while it will cause local effects on the body. Another main difference between both nervous systems is the regeneration process of nerves, which is not possible in CNS (in most cases) while it is possible in PNS (most of the nerves). Except these, they also differ in terms of components, nerve axons, etc.

CNS or Central Nervous System is the system that has two components or is consists of the brain and spinal cord. It is said to be central due to its function of combining and receiving sensory information from the entire body. It is responsible for several functions of the body, which include walking, standing, running, etc. many nerves in this are incapable of regeneration.

PNS, or Peripheral Nervous System, is the system that plays an important role in conveying messages and information to the central nervous system. Therefore it is important for carrying out involuntary functions and activities in the body. The involuntary function includes that body performs without intentions, such as breathing, sensing, hurting, etc.

Comparison Table Between CNS and PNS

Parameters of ComparisonCNSPNS
FunctionControl voluntary functionsControl involuntary functions
ComponentsBrain and spinal cordSensory receptors, sensory neurons, and motor neurons.
Nerve AxonsSlender projectionsLong nerve fibers
DamageCause global effectCause local effect
Regeneration of Nerves  Most are incapable of regeneration.Most are capable of regenerating.

What is CNS?

It consists of the brain (100 billion nerve cells) and the spinal cord. Cells are protected by meninges and the skull. It can be divided into four lobes: parietal (responsible for sensory information), temporal (memory and learning purposes), occipital (receives visuals), and frontal (responsible for voluntary movements). The spinal Cord starts on the base and is protected by the vertebral column. It performs the functions that include PNS. It is composed of several components, they are:

  • Eight Cervical Segments.
  • Twelve Thoracic Segments.
  • Five Lumbar Segments.
  • Five Sacral Segments.
  • One Coccygeal Segment.

It is divided into white (inner area of cortex) and gray matter (outer cortex). The following are also part of it:

  • optic nerve
  • retina
  • olfactory epithelium
  • and olfactory nerves.

Following are some of the diseases that can affect the Central Nervous System of an individual:

  • Trauma: it depends upon the injury and can make a person paralyzed.
  • Infections: some micro-organisms can lead to many diseases.

What is PNS?

It is responsible for communication between CNS and organs by sending a sensory signal to the brain and provides a response to the body. It is composed of ganglia (neurons and neurons clusters). It can be divided into the following:

  1. Somatic Nervous System: it is responsible for controlling the actions and reflexes of the body. Afferent fiber is responsible for carrying sensory signals, and organs connected to it are the eye, tongue, nose, skin, and ear. Efferent carries instructions to the organs through CNS. 
  2. Autonomic Nervous System: it controls involuntary and unconscious movements of the body. Two parts of it are the sympathetic and parasympathetic nervous systems. 

Following are some facts of PNS:

  • It consists of 500 million neurons responsible for controlling the stomach and intestines. 
  • It is said to be very slow. For example, you feel pain after realizing the fact you have hit it.

It is related to CNS also; therefore, if this nervous system is damaged due to any reason, it will affect CNS and body.

Main Differences Between CNS and PNS

  1. The main difference between CNS and PNS is in the functions they are responsible for. They are responsible for different types of functions in the body. CNS is responsible for controlling voluntary functions. Voluntary functions include urination and swallowing, etc., whereas PNS is responsible for involuntary functions. These include digestion, heart beating, breathing, etc.
  2. They consist of different components. Central Nervous System consisting the brain and spinal cord, whereas the Peripheral Nervous System consists of varieties of neurons and receptors, for example, sensory receptors, sensory neurons, and motor neurons.
  3. In terms of Nerve Axons, CNS nerve axons carry particular short nerve impulses (which are connected to spinal cords and brain) as it is consist of slender projections, while Peripheral Nervous System has long nerve fibers which can go up to a length of 1 m.
  4. Any damage caused to these nervous systems can lead to serious causes. In the case of the central nervous system, any damage that happens to it will cause global effects as it leads to major and voluntary functions of the body, while in the case of the peripheral nervous system, any damage caused to it will cause local effects on the body as it controls involuntary functions of the body.
  5. Some nerves are capable of regenerating, and the CNS and PNS differ in terms of regeneration. The regeneration process is not possible with most of the nerves present in CNS, while it is possible in the case of PNS.

Conclusion 

Therefore, there should not be any difficulty in understanding the role and functions of the body. They can be misunderstood due to their similarities, such as both of them are part of the nervous system of vertebrates, they are responsible for giving response to the environmental stimuli, they comprise of neurons with same physiology. Any damage to them will affect the whole body, and it will be difficult for a person to perform simple things. The main difference between the central nervous system and peripheral nervous system is in their role and functions in the body.

There are other nervous systems as well; they are Somatic Nervous System, Autonomic Nervous System, etc. they all are connected to CNS and PNS directly or indirectly.

References 

  1. https://www.sciencedirect.com/science/article/pii/S0012160698989138
  2. https://journals.biologists.com/dev/article-abstract/127/5/1039/41210
  3. https://www.hindawi.com/journals/mi/2015/251204/
  4. https://www.sciencedirect.com/science/article/pii/0165572892901347
  5. https://www.sciencedirect.com/science/article/pii/0169328X8890006X
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