Difference Between Sympathetic and Parasympathetic

Introduction to the autonomic nervous system

The nervous system is an important system that plays an important role in every action of life and is responsible for all involuntary and voluntary actions of our body. It constitutes the nerve network, spinal cord, and brain and is classified into three divisions. The central nervous system, autonomic nervous system, and peripheral nervous system are the three divisions of the nervous system.

Autonomic nervous system control and regulates the involuntary function of the internal organs. This function is done without a person's conscious effort. The autonomic nervous system is segregated into sympathetic and parasympathetic systems. The sympathetic nervous system with the help of the spinal cord connected the internal organs to the brain. When these sympathetic nerves are stimulated they prepare the body for stress-related activities. The stress is accompanied by some actions in the body like increased heart rate, blood flow in the blood vessels, and decreased blood flow rate in the skin. The vagus nerve and lumbar spinal nerve are the nerve fibres of the parasympathetic nervous system. When these parasympathetic nerves are stimulated it reduces the heartbeat and increased digestive secretion. Many of the internal organs are either controlled by parasympathetic or sympathetic nerves. In a few cases, the parasympathetic and sympathetic nervous system has opposite effects on the same organ. These two divisions work together to make sure that in different situations body will act appropriately.

Sympathetic Nervous system

The sympathetic nervous system is one of the subdivisions of the autonomic nervous system. It plays a vital role in controlling and regulating the autonomic processes. This system prepares the body how to prepare itself for emergency situations or any other stress-related situation. In a stressful environment, the sympathetic nervous system slows down some process that is less important during this time such as digestion. These processes are not under persons' conscious effort. The sympathetic nervous work together with the parasympathetic nervous system to maintain homeostasis. This is the balance for internal physiological mechanisms which is very important for all the living organisms on the earth.

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Features

• Increase heart rate
• Dilation of pupils
• Secretions of sweat from the sweat gland
• Expansion of muscles
• Alertness increases
• Slow down the digestion process
• Relaxation of the bladder

Functions

• Activate fight or flight response in case of emergency − Sympathetic nervous system activates flight or fight response in case of emergency. For example, if we walk down a road at night time and suddenly a stranger comes and approaches us in this situation body can react in two ways either fight with the situation or run away from this. In this condition, SNS would activate the action by causing the eyes to dilate, increase heart rate, secretion of sweat, and increase alertness. In contrast, SNS slows the digestion process as it is not required in times of emergency.

• Regulate body temperature − The sympathetic nervous system regulates the body temperature to maintain an equilibrium.

• Regulate cardiovascular effect − The sympathetic nervous system regulates small changes in cardiovascular effect. The cardiovascular activities need to change in the time of exercise, changing posture, from transitioning from sleep to being aware.

Parasympathetic nervous system

The parasympathetic nervous system is another subdivision of the autonomic nervous system. This nervous system mainly controls the secretion of glands. The vagus nerve and lumbar spinal nerve are the nerve fibres of the parasympathetic nervous system. When these parasympathetic nerves are stimulated increased digestive secretion and reduce heartbeat.

The parasympathetic nervous system is well organized. Preganglionic and postganglionic neurons constituents motor components. The location of preganglionic neuron cells is in specific cells, in the brainstem, or in the lateral horns of the spinal cord. The preganglionic axon which is arisen from the brainstem extent to the parasympathetic ganglia. The location of parasympathetic ganglia is the head or near the heart and embedded in the trachea, bronchi, and gastrointestinal tract or placed near the urinary bladder.

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Features

• Decrease heart rate
• Decrease blood pressure
• Increase digestion process
• Increased production of mucus and saliva
• Increase urine secretion
• Tightening of bronchial muscles

Functions

• The parasympathetic nervous system is capable of decreasing the heart rate. It decreases heart rate during the resting period either after physical exercise or after an emergency situation when the heart would be beating faster.

• The parasympathetic nerves help in the production of tears.

• The parasympathetic nerves trigger salivation in the mouth.

Similarities between the sympathetic and parasympathetic nervous systems

Both the sympathetic and parasympathetic nervous systems are the subdivision of the autonomic nervous system. They mainly control all the involuntary functions of the body including physiological processes like circulation, respiration, reproduction, urination, and digestion. Both sympathetic and parasympathetic nervous system pathways are composed of preganglionic and postganglionic neurons and maintain the homeostasis of the body.

Difference between the sympathetic and parasympathetic nervous system

Sympathetic nervous system	Parasympathetic nervous system
Increase heart rate, and blood pressure and constrict blood vessels	Decrease heart rate, increases urination.
Prepares the body in an emergency situation	Relax the body after emergency
Its a quick response	Its a slow response
Close the CNS ganglions are found	Away from CNS ganglions are found
In the target area creates a diffuse effect	In target area it creates a localized effect
Sensory awareness increases	Sensory awareness at normal level
Dilates the pupil of the eye	Contracts the pupil of the eye.
Inhibits the saliva secretion	Stimulates the secretion of saliva and digestion

Conclusion

Autonomic nervous system regulates the involuntary functions of the body. It is segregated into two parts namely sympathetic and parasympathetic nervous systems. The sympathetic nervous system stimulates the body in case of an emergency. It increases heartbeat and slows the digestive process as it is not essential in an emergency. The primary function of the sympathetic nervous system is to activate the fight or flight response. While the parasympathetic nervous system prepares the body to relax after an emergency it increases digestion and urination. This system is also known as the rest and digest system as its main function is to restore the body's natural activity and relax the person once the emergency situation is over. These two divisions of the autonomic nervous system work together to make sure that in different situations body will act appropriately.

FAQs

Q1. What is the function of the vagus nerve?

Ans. The vagus is the main nerve of the parasympathetic nervous system. It mainly controls the involuntary functions of the body. These involuntary functions included heartbeat, digestion, urination, etc. Apart from these activities to some extent, they regulate some reflex actions like coughing, sneezing, and vomiting.

Q2. How do the sympathetic nervous system regulates body temperature?

Ans. By using fat reserves in the body the sympathetic nervous system regulates body temperature. It uses these reserves to increase the production of heat in the body by changing the blood flow into the skin. It is also able to cool down the body by stimulating the sweat gland.

Q3. What is the urinary bladder?

Ans. The urinary bladder of the excretory system stores urine. Its size and shape vary depending upon the amount of urine it contains and the pressure it gets from the surrounding organs

Q4. What is saliva?

Ans. Saliva is the watery secretion of the salivary gland which helps in the digestion of food. It lubricates and cleans the mouth.

Q5. What is a pupil of the eye?

Ans. It is the round opening that is situated in the iris of the eye. It allows the light to strike the retina. In bright light, pupil sizes become reduced while their sizes increase when the amount of light decreases.