CNS vs PNS: Difference and Comparison

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.


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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, CNS and PNS, carry out most of the body functions.

Key Takeaways

  1. CNS is responsible for the brain and spinal cord, while PNS is responsible for the rest of the body.
  2. CNS is responsible for controlling voluntary and involuntary actions, while PNS is responsible for carrying sensory information to the CNS.
  3. CNS is more protected than PNS because it is encased in bone and surrounded by cerebrospinal fluid.


CNS stands for Central Nervous System and is a system in the body that consists of the brain and spinal cord, which is in charge of combining and receiving sensory information. PNS, meaning Peripheral Nervous System, is a system in the body that carries out involuntary functions like breathing, hurting, and sensing.


CNS, or Central Nervous System, is a system that has two components or 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 the body performing without intentions, such as breathing, sensing, hurting, etc.

Comparison Table

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 the 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 providing a response to the body. It is composed of ganglia (neurons and neuron 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 fibre is responsible for carrying sensory signals, and the organs connected to it are the eye, tongue, nose, skin, and ear. Efferent carries instructions to the organs through the 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 about 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 the CNS also; therefore, if this nervous system is damaged due to any reason, it will affect the CNS and the 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, heartbeating, breathing, etc.
  2. They consist of different components. The Central Nervous System consists of 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 the brain) as they consist of slender projections, while the Peripheral Nervous System has long nerve fibres that 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.

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