How Does the Peripheral Nervous System Work?
In this article on the nervous system, students will learn about the functions, parts, and disorders of the peripheral nervous system. But first, let us understand what a nerve is.
A nerve is basically a bundle of fibers that are composed of cord-like structures called neurons. So now, what are neurons? The body of a neuron is located in the central nervous system which has a body and an axon out of which the axon is embedded in the muscles and sensory organs. Therefore, a nerve sends electrical and chemical signals through these neurons to send sensory or motor information from one part of the body to another. Nerves are the main components of the entire peripheral nervous system.
The function and communication system of the body is controlled by the nervous system. There are two parts of the nervous system; these are the peripheral nervous system and the central nervous system. The nerves, spinal cord, and ganglia are included in the peripheral nervous system. This nervous system serves as the link between the central nervous system, limbs, and organs. There are two kinds of nerve fibers which are known as afferent and efferent fibers. It connects the brain, spinal cord with the body. The response and information are brought from the brain and spinal cord to CNS via the pathway of the nervous system.
Peripheral Nervous System Location
The components of the peripheral nervous system are the nerves and ganglia that are present outside the spinal cord and the brain.
Peripheral Nervous System Function
Organs and limbs are connected to the central nervous system, essentially assisting as a relay between the spinal cord, the brain, and the rest of the body which is the main function of the PNS.
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Classification of Peripheral Nervous System
The two parts of the peripheral nervous system are named the Somatic Nervous System and the Autonomic Nervous System.
1. Somatic Nervous System- The impulse is transferred to skeletal muscles from the central nervous system via the help of the Somatic Nervous System. Cranial and spinal nerves are also termed as the major components of the Somatic Nervous System. It is responsible for carrying messages from the outer area of the body.
The somatic nervous system is made up of two kinds of neurons, one type is called the sensory neurons or afferent neurons and the other kind is known as motor neurons or efferent neurons. The afferent neurons are responsible for transmitting messages to the central nervous system where the data is then processed while the afferent neurons are responsible for relaying information from the central nervous system to different parts of the body via muscles.
Cranial Nerves- These nerves are found to emerge from the brain. From the brain, around 12 pairs of cranial nerves emerge. The names of all 12 cranial nerves are as follows: Olfactory nerve, Optic nerve, Oculomotor nerve, Trochlear nerves, Trigeminal nerves, Abducens nerves, Facial nerve, Vestibulocochlear nerve, Glossopharyngeal nerve, Vagus nerve, Accessory nerve, Hypoglossal nerve.
Spinal Nerves- They emerge from the spinal cord. This nerve has thirty-one pairs. They move towards the area of ventral and dorsal roots. Between two roots, there is a junction where the sensory fibers and the motor fibers continue into the dorsal root and ventral root respectively.
2. Autonomic Nervous System- The response which comes from the central nervous system is passed on to the smooth muscles and involuntary organs of the body via the pathway of the autonomic nervous system. It also has two further divisions which are known as the sympathetic and parasympathetic nervous systems.
Sympathetic Nervous System- There are nerves that arise from the spinal cord. It is found to be located between the neck and the waist region. Adrenalin is responsible for stimulating the sympathetic nervous system. It is responsible for preparing the body against all the violent actions which can take place during the abnormal conditions of the body.
Parasympathetic Nervous System- The location of the parasympathetic nervous system is anterior in the neck and head. On the other side, the location of the posterior is the sacral region. This nervous system is totally responsible for re-establishing the normal condition in the body when the violent action gets over.
Role of the Peripheral Nervous System
The internal homeostasis is regulated by this nervous system.The release of secretions from exocrine glands is controlled by the peripheral nervous system.The brain and the spinal cord are connected to the body and the outer environment through the pathway of the peripheral nervous system. It works as a connecting link between the central nervous system, organs, skin, and limbs of the body. The complex behavior and movements are controlled by the peripheral nervous system. When any kind of sensation is felt within any part of the body then it’s carried to the CNS by the help of the skin’s sensory receptor. Then the signal is taken to the sensory organs.Involuntary muscles are found to be controlled by autonomic motor cells.
Disorder of the Peripheral Nervous System
Around a hundred kinds of disorders can happen in the peripheral nervous system. One or more nerves can be affected due to this. Some diseases like Guillain-Barre syndrome, diabetic nerve problems, thoracic outlet syndrome, etc can be the result of other diseases or virus infection. Sometimes, an injury can cause problems like complex regional pain syndrome. In some cases, the disorder can be found to be caused due to genetic inheritance. These kinds of disorder symptoms become unnoticeable but get worse quickly. Individuals should practice regular exercises and yoga in order to cure such disorders as it will help in reducing pain.
Treating Damage of Nerves
Although treatment and cure of damaged nerves is in high demand, it cannot be healed completely. There are various treatments available to reduce the severity and symptoms of nerve damage but it is not completely useful. One should always consult a doctor if the nerve damage is often too progressive as it may lead to irreversible damage if left untreated and untended. But there are a few things that one can do that might help lessen the pain.
Vitamins: Deficiency of Vitamin B can lead to nerve damage so it is advisable to take sufficient amounts of vitamin B through foods. Vitamin D is also helpful to prevent nerve pain.
Taking warm baths
Doing yoga and exercise
Mediation
Eliminating Bad Habits: Smoking constricts the blood vessels and decreases the amount of oxygenated blood that can pass through. This may lead to other serious conditions such as numbness and pain from peripheral neuropathy. Therefore, it is highly advisable to quit smoking.
FAQs on Peripheral Nervous System: Definition, Functions & Types
1. What is the Peripheral Nervous System (PNS)?
The Peripheral Nervous System, or PNS, is one of the two major divisions of the nervous system. It consists of all the nerves and ganglia located outside the brain and spinal cord (the Central Nervous System). Its primary role is to act as a communication network, connecting the CNS to our limbs, organs, and senses.
2. What are the main functions of the Peripheral Nervous System?
The PNS has several vital functions:
Relaying Sensory Information: It carries sensory signals from the body (like touch, pain, and temperature) to the Central Nervous System for processing.
Transmitting Motor Commands: It sends motor commands from the CNS to the muscles and glands, enabling movement and bodily responses.
Controlling Voluntary Actions: Through the somatic nervous system, it controls conscious movements like walking and writing.
Regulating Involuntary Functions: Through the autonomic nervous system, it manages essential background functions like heartbeat, digestion, and breathing.
3. How does the Peripheral Nervous System differ from the Central Nervous System (CNS)?
The primary difference lies in their components and function. The CNS consists of the brain and spinal cord and acts as the body's main processing and control centre. In contrast, the PNS includes all other nervous tissue and functions as the communication network that relays information between the CNS and the rest of the body. The CNS interprets information, while the PNS transmits it.
4. What are the two main divisions of the PNS?
The Peripheral Nervous System is broadly divided into two main parts:
The Somatic Nervous System (SNS): This division is responsible for carrying sensory and motor information to and from the CNS and is generally associated with voluntary control of skeletal muscles.
The Autonomic Nervous System (ANS): This division is responsible for regulating involuntary bodily functions such as heart rate, digestion, respiratory rate, and pupillary response. It operates automatically without our conscious control.
5. What are cranial nerves and spinal nerves?
Cranial and spinal nerves are the fundamental components of the PNS. Cranial nerves (12 pairs) emerge directly from the brain and brainstem, primarily serving the head and neck. Spinal nerves (31 pairs) emerge from the spinal cord, branching out to serve the rest of the body.
6. What are the roles of the sympathetic and parasympathetic nervous systems?
These are the two subdivisions of the Autonomic Nervous System, and they have opposing effects:
The Sympathetic Nervous System prepares the body for the 'fight-or-flight' response during times of stress or danger. It increases heart rate, dilates pupils, and redirects blood to muscles.
The Parasympathetic Nervous System controls the 'rest-and-digest' functions. It conserves energy by slowing the heart rate, increasing intestinal activity, and relaxing the body after the emergency has passed.
7. Why is the control exerted by the Autonomic Nervous System considered 'involuntary'?
The control is considered involuntary because it regulates core bodily functions that are essential for survival and must operate continuously without conscious thought or effort. Processes like heartbeat, breathing, and digestion are too critical to be left to conscious control, so the ANS manages them automatically to maintain homeostasis (internal stability).
8. Are cranial nerves part of the CNS or the PNS? Explain why.
This is a common point of confusion. Despite originating from the brain (a CNS component), the cranial nerves are part of the Peripheral Nervous System. The definition of the PNS includes all nerves and ganglia outside the brain and spinal cord. Since the cranial nerves extend beyond the brain to relay information, they fit the definition of peripheral nerves.
9. How does the 'fight-or-flight' response, controlled by the sympathetic system, demonstrate the importance of the PNS?
The 'fight-or-flight' response is a perfect example of the PNS in action. When a threat is perceived, the CNS makes a decision, but it is the sympathetic division of the PNS that executes the physical response. It rapidly transmits signals to various organs to:
Increase heart rate to pump more blood.
Dilate the pupils to improve vision.
Redirect blood flow from the digestive system to the skeletal muscles.
Trigger the adrenal glands to release adrenaline.
This coordinated, high-speed action by the PNS is crucial for survival in dangerous situations.
10. What happens if the peripheral nerves get damaged?
Damage to peripheral nerves, a condition known as peripheral neuropathy, disrupts the communication link between the CNS and the body. This can lead to a range of symptoms depending on which nerves are affected. Common consequences include numbness or tingling, sharp pain, muscle weakness, lack of coordination, and problems with involuntary functions like blood pressure regulation or digestion.
