Peripheral Neural System: Types (Somatic and Autonomic) and Function

The peripheral nervous system along with the central nervous system is a part of the nervous system. The nervous system is a network of nerves and cells that send and receive information from the brain and spinal cord to other areas of the body. It is referred to as the regulating mechanism of the body. The central nervous system is made up of the brain and spinal cord while the peripheral nervous system consists of autonomic and peripheral nervous systems. There are two kinds of nerve fibers in our body afferent and efferent nerve fibers. The network of nerves that link the brain and spinal cord is known as the peripheral nervous system. In this article, we will have a look at the peripheral nervous system, understand its structure and functions.

What is Peripheral Nervous System?

The nervous system regulates the body's function and communication system. The nervous system is divided into two parts: the peripheral nervous system and the central nervous system. The peripheral nervous system includes the nerves, spinal cord, and ganglia. The nervous system's route transports responses and information from the brain and spinal cord to the CNS. The communication between CNS and the body is handled by the peripheral nervous system. The peripheral nervous system is mainly made up of a network of nerves. The nerves in our peripheral nervous system are of two types: afferent and efferent nerve fibers. 

• The afferent nerve fibers are in charge of transmitting impulses from the tissues to the central nervous system.
• The efferent nerve fibers are in charge of transmitting impulses from the central nervous system to the tissues or organs in question.

The peripheral nervous system consists of:

• The somatic nervous system which is made up of nerves that go from the brain to the skin and muscles and play a role in conscious actions. 
• The autonomic nervous system which comprises nerves that connect the CNS to visceral organs like the heart, stomach, and intestines. It acts as a conduit for unconscious actions.

Divisions of Peripheral Nervous System

The peripheral nerve system is comprised of two main systems which are:

1. Somatic Nervous System
2. Autonomic Nervous System

Somatic Nervous System

The somatic nervous system's primary purpose is to transmit impulses from the central nervous system to the skeletal muscles. The primary components of the Somatic Nervous System are the cranial and spinal nerves. It is in charge of relaying messages from the outside of the body.

It consists of:

1. Cranial Nerves

The inferior surface of the brain has twelve pairs of cranial nerves. Except for the vagus nerve, all of these nerves go via foramina in the skull to innervate tissues in the head, neck, and face.

• According to the sequence in which they emerge on the inferior surface of the brain, the cranial nerves are named and assigned Roman numerals. 
• The majority of nerves have both sensory and motor functions. 
• Only sensory fibers go through three of the nerves, which are linked with the unique senses of smell, vision, hearing, and balance. 
• Five additional nerves are mainly motor in nature, but they do contain some proprioceptive sensory fibers.
• The remaining four nerves include a large number of sensory and motor fibers.
• The balance nerve, commonly known as the eighth cranial nerve or vestibulocochlear nerve, produces benign fibrous growths termed acoustic neuromas. 
• These tumors are non-malignant, which means they don't spread or spread to other regions of the body. These tumors are found deep within the skull, close to critical brain regions in the brain stem. As tumors grow larger, they engulf neighboring structures that perform critical activities. These tumors, in the vast majority of instances, develop slowly over time.

In certain situations, the rate of development is quicker, and individuals acquire symptoms more quickly. The symptoms are usually minor, and many individuals are not detected until their tumor has progressed. When patients are tracked by yearly MRI scans, many of them show no tumor development over time.

2. Spinal Nerves

The spinal cord has thirty-one pairs of spinal nerves that exit laterally. Each nerve pair corresponds to a section of the spinal cord and is referred according to that. There are eight cervical nerves, twelve thoracic nerves, five lumbar nerves, five sacral nerves, and one coccygeal nerve in all.

A dorsal root and a ventral root link each spinal neuron to the spinal cord. Sensory neuron cell bodies are found in the dorsal root ganglion, whereas motor neuron cell bodies are found in the grey matter. Just before the nerve leaves the vertebral column, the two roots unite to create the spinal nerve. All spinal nerves are mixed nerves because they contain both sensory and motor components.

Autonomic Nervous System

The autonomic nervous system is responsible for sensing and controlling involuntary actions. It's in charge of keeping an eye on the internal environment and making necessary modifications. In general, the autonomic nervous system is in charge of all internal bodily functions that occur without your conscious knowledge or active participation.

The autonomic nervous system is made up of sensory and motor nerves that connect the central nervous system (particularly the hypothalamus in the brain) to internal organs (including the heart, lungs, and digestive organs) and glands (such as the sweat glands and pancreas). 

• The autonomic nervous system's sensory neurons monitor interior body circumstances and transmit information to the brain. 
• The autonomic nervous system's motor neurons regulate the contractions of smooth or cardiac muscle, as well as glandular tissue.

When the autonomic nervous system detects a rise in body temperature, motor neurons instruct smooth muscles in blood vessels near the body surface to dilate, and sweat glands in the skin generate more perspiration to cool the body.

Somatic vs autonomic nervous system

The sympathetic and parasympathetic divisions of the autonomic nervous system are two subdivisions of the autonomic nervous system.

It is split into two sections:

• Sympathetic Nervous System
• Parasympathetic Nervous System

Both divisions supply fibers to a large number of visceral organs. One stimulates and the other inhibits, in this situation. This antagonistic functional connection helps to preserve homeostasis by providing a balance.

Sympathetic Nervous System 

It is made up of nerves that originate in the spinal cord. It is discovered in the area between the neck and the waist. The sympathetic nervous system is stimulated by the hormone adrenalin. It is in charge of preparing the body for any aggressive acts that may occur as a result of aberrant bodily circumstances.

Parasympathetic Nervous System 

It is found in the neck and head. The sacral area, on the other hand, is the site of the posterior. When the violent activity is complete, this nerve system is entirely responsible for restoring the body's normal state.

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Functions of Peripheral Nervous System

The functions of the peripheral nervous system are:

• This nerve system is in charge of maintaining internal homeostasis.
• The peripheral nervous system regulates the release of secretions from exocrine glands.
• The peripheral nervous system connects the brain and spinal cord to the rest of the body as well as the outside world. 
• It serves as a connection between the body's central nervous system, organs, skin, and limbs. 
• The peripheral nerve system is in charge of complicated behaviour and motions.
• Any feeling felt in any region of the body is transmitted to the CNS via the sensory receptor of the skin. The signal is then sent to the sense organs.
• Autonomic motor cells are discovered to govern involuntary muscles.
• The PNS is responsible for voluntary actions including chewing, walking, and facial expressions. 
• The PNS also controls autonomic activities including breathing, heart rate, and digestion, which are all automatic physiological functions.

As a result, the PNS is critical for human survival. The nerves and cells of the PNS are not covered by bones, unlike the CNS, which is protected by the skull and vertebrae of the spine. As a result, the PNS is more vulnerable to trauma.

Disorder of the Peripheral Nervous System

The peripheral nervous system can be affected by over a hundred different diseases. This can cause damage to one or more nerves. 

1. Guillain-Barre syndrome, diabetic nerve issues, thoracic outlet syndrome, and other illnesses can be caused by other diseases or viral infections.
2. An injury can sometimes result in complications such as complicated regional pain syndrome.
3. In certain situations, the condition may be traced back to a genetic mutation.
4. The signs of many disorders go unnoticed at first, but they progressively worsen.
5. In order to heal such diseases, people should engage in regular workouts and yoga, which will assist to reduce discomfort.

Symptoms of Peripheral Nerve Disorder

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Things to Remember

• All nerves branching out of the brain and spinal cord makes up the peripheral nervous system (PNS).
• Spinal nerves and cranial nerves are the two primary kinds of nerves of the peripheral nervous system. 
• The autonomic and somatic nervous systems are two functional divisions of the PNS. Both of these may be split further, with the former being divided into sympathetic and parasympathetic arms and the latter being divided into sensory and motor divisions.
• Nerves and ganglia are the tissues that make up the PNS. Ganglia are nerve tissues that serve as relay sites for messages sent through the PNS's nerves. 
• The bulk of PNS tissues are made up of nerves, which are cable-like bundles of axons. 
• Sensory, motor and mixed nerves are the three types of nerves that convey nerve signals in different directions.
• Sensory nerves provide information from the body's sensory receptors to the CNS. Afferent nerves are another name for sensory nerves.
• Motor nerves provide information from the central nervous system (CNS) to muscles, organs, and glands. Efferent nerves are another name for motor nerves.
• Sensory and motor neurons coexist in mixed nerves, allowing them to send information in both directions. Both afferent and efferent functions are performed by them.