Our nervous system consists of two components ie. the Central Nervous System (CNS) and the Peripheral Nervous System (PNS). The central nervous system consists of the brain, spinal cord, and neurons. The nervous system exchange sensory signals with the CNS. The major role of the CNS is to receive information from different parts of the body and coordinate them in order to generate the body’s responses.
The Peripheral Nervous System (PNS) consists of all the nerves that lie outside the brain and the spinal cord. In other words, it includes all the nerves that are outside the central nervous system (CNS). The main aim of PNS is to link the central nervous system with the other parts of the body like organs, skin, and limbs. With the help of the PNS, CNS is able to connect with the entire body.
The peripheral system receives and sends information to the brain as well as the spinal cord and helps in transferring the information to the other parts of the body. This is performed with the help of the nerves that carry signals from the sensory receptors present in the ears, eyes, nose, skin, as well as the receptors present in various internal organs like muscles and glands. Once the sense organs ascertain the change in the environment, they communicate the signal to the CNS with the help of sensory nerves. Then the brain sends signals by the nerves to the muscles, which helps the muscles to react. Therefore, it can be said that the exchange of information among the PNS, CNS, and the body keeps on happening as a nerve impulse. Thus, PNS can be considered vital for human survival as the system is not secured by the skull, unlike the CNS. This makes the peripheral system more prone to external harm.
Components of Peripheral Nervous System
The peripheral nervous system is made up of two main components: the somatic nervous system and the autonomic nervous system. The somatic nervous system (SNS) comprises nerves that are connected with the sensory receptors and the voluntary skeletal muscles. It helps in regulating conscious or voluntary actions like chewing and walking. The autonomic nervous system (ANS) is further divided into two systems. It regulates important functions like breathing and digestion.
Somatic Nervous System
The somatic nervous system is related to actions or activities carried out consciously or voluntarily like eating, running, etc. It is the main system that carries messages in the entire body to initiate and maintain movements. SNS can be considered vital for almost all voluntary muscle movements. It also processes motor as well as sensory information that reaches the system through external stimuli like sight, touch, and hearing which then sends and receives signals to the central nervous system. This helps in controlling voluntary movements and interpreting sensory information or signals.
Since the SNS is involved in the exchange of motor and sensory information with the CNS, it includes two types of neurons: motor neurons or efferent neurons and sensory neurons or afferent neurons.
Motor neurons are also known as efferent neurons. They are responsible for transmitting information from the brain and spinal cord to the skeletal and the muscle fibers in the entire body to control the muscle movements either directly or indirectly. Motor neurons also enable the human body to react to external stimuli.
For example, while food tasting, sensory neurons send a signal to the brain. The brain then transmits the same with the help of motor neurons and signals the mouth to continue eating.
The somatic nervous system is also important for reflexes. Reflex is an involuntary muscle response that is controlled by a reflex arc. For example, while touching a burning surface the brain directly sends a motor signal to retract the hand from the surface.
Sensory neurons are also known as afferent neurons. They are responsible for transmitting information either from muscles, glands, and other internal organs or from external stimuli like heat, sound, and light to the central nervous system. For example, while feeling a harsh surface the signal will be transferred to the brain via the sensory neurons.
The somatic nervous system is also important for reflexes. Reflex is an involuntary muscle response that is controlled by a reflex arc. For example, while touching a burning surface the brain directly sends motor signals to retract the hand from the surface.
Autonomic Nervous System
The autonomic nervous system helps in coordinating involuntary actions like heartbeat, digestion, and breathing. The nervous system enables them to work on their own or automatically. The autonomic nervous system controls various internal processes like urination, body temperature, metabolism, production of body fluids like saliva, sexual response, and others. Two main neurotransmitters that are vital for communication in the autonomic nervous system are acetylcholine and norepinephrine. The system is further divided into two sub-categories: the sympathetic nervous system and the parasympathetic nervous system.
Sympathetic Nervous System
The sympathetic nervous system is responsible for regulating flight or fight response. This happens when the body needs to react to an intimidating situation. Due to such situations, the system reacts by increasing heartbeat, increasing blood flow, and activating sweat glands. All these responses prepare an individual for the coming situation. It also responds by slowing down other bodily processes that are insignificant at that time.
Parasympathetic Nervous System
The parasympathetic nervous system aids in maintaining usual bodily functions by either reducing the activity or regulating it. It comes into play when the threatening situation ends. At this point, the body works to reach the normal or the resting state. To achieve this, the nervous system manages the heart rate, signals the sweat glands to stop, and decreases blood flow. This signifies that the body is now entering the normal state and the prevailing dangerous situation has ended.
To ensure smooth functioning of the body, both the systems ie. the sympathetic nervous system as well as the parasympathetic nervous system have to work in opposite ways in order to maintain the body’s equilibrium also known as homeostasis.