Let’s discuss some of the ways our actions are impacted by our nervous system which comprises the central nervous system and peripheral nervous system

1. The impacts of sympathetic and parasympathetic
nervous system
Human Nervous system
The human nervous system is a very fascinating organ controlling sensory
and hormonal regulation and maintaining the homeostatic balance in the
body.
Here you can read all about the basic functions of the human nervous
system and a detailed review on the parasympathetic and sympathetic
nervous systems. Do you wish to learn more comprehensive asp ects of the
human nervous system? Our private biology tutors provide detailed lectures
as per your requirement.

2. Whether it is a voluntary action or involuntary action, they are all controlled
by the nervous system. From your movement to your perception and thought
process, all your major bodily functions are controlled by the nervous
system.
Impact of the nervous system
A lot of our actions are controlled by our nervous system. All t he
components of our nervous system including the brain, spinal cord, somatic,
and autonomic nervous system are actively working for the right body
functions.
Let’s discuss some of the ways our actions are impacted by our nervous
system which comprises the central nervous system and peripheral nervous
system:
1. Every individuals’ perspective differs based on their stimulus -response
by their nervous system. We see, taste, and smell things based on our
nervous system’s perception of our surroundings.
2. The movement of our skeletal system is controlled by the nervous
system.
3. The way we express our emotions such as crying, laughing, and much
more.
4. The storing and retrieving of information based on our memory.
5. The hormonal regulation in the body such as homeostasis, puberty.
Classification of the nervous system
The human nervous system is classified into two main parts that include:

3. • Central nervous system
This further includes the brian and spinal cord
• Peripheral nervous system
This further includes the somatic and autonomic nervous systems.
Autonomic Nervous System
Just like we associate terms with their names, the functions of the autonomic
nervous system are also associated with its name. The many autonomic
functions in our body that we are usually not in control of, are controlled by
the autonomic nervous system.
The autonomic nervous system is further classified into two main parts
including

4. 1. The sympathetic nervous system
2. The parasympathetic nervous system
Sympathetic nervous system
The sympathetic division is mainly associated with the flight or fight
response of the body when the body’s response is usually associated with
stress or pressure. Whenever there is a situation that is perceived as
dangerous or stressful by us, the response to it is generated by the
sympathetic nervous system.
The sympathetic nervous system is comprised of certain cell bodies that
work to increase the blood flow to the muscles and accelerate the heart rate
so basically whenever you are feeling a bit anxious, stressed, or
experiencing a sudden panic attack, these all are responses by your
sympathetic nervous system.

5. Location
The sympathetic nervous system is located near the middle of the spinal
cord. It starts from the first thoracic vertebra and goes forward till the
second or their lumbar vertebra. It can be found near the thoracic and
lumbar regions.
Working of the system
The sympathetic nervous system is responsible for preparing us for any
dangerous or stressful situation that we might be encountering. This
response by the sympathetic nervous system is achieved by a series of
complex steps involving neurons, hormones, and other body organs
including the skeletal system, gastrointestinal tract, and cardiac muscles.

6. After the sympathetic nervous system increases the release of stress
hormones including adrenaline and noradrenaline, there are a series of
changes in your bodily functions that you feel suddenly. These changes
include
• The increased rush of blood flow to t he heart and brain.
• The blood flow makes the heart beat faster.
• The faster heartbeat makes you breathe faster.
• The blood moves from skin and stomach to brain and heart, leaving
the skin feeling cold and experiencing goosebumps and giving you an
upset digestive feeling.
The impulse response is secreted by the sympathetic nervous system which
in turn regulates the hormonal response. That response actively changes the
physiological functions of the gastric, skeletal, and cardiac systems of the
body. sympathetic and parasympathetic nervous system.
Hormonal release
As a result of a stressful situation, there is a sudden release of certain
hormones that are associated with the stress factor in the body.
Bidirectional flow of messages
There is a bidirectional flow of messages associated with the sympathetic
nervous system. As the sympathetic nervous system send the stress
response to the body to release hormones, the release of certain hormones
and their action on the other body organs are in return a response of th e
body to the sympathetic nervous system.

7. This is how there is a bidirectional flow of information going through the
sympathetic nervous system to the body and then from the body to the
sympathetic nervous system.
Roles and functions
Several different functions are performed by the sympathetic nervous
system to ensure that the body is functioning right as a result of a stressful
or alarming situation, making it a quick response mobilizing system.
The fight or flight response
The sympathetic nervous prepares the body for any dangerous or stressful
situation by the action of fight or flight response. With the action of fight or
flight response, the body gets prepare d to face a certain situation. Based on
the decision, we either fight it or flee from it. This is how fight or flight
response works that are generated by the sympathetic nervous system when
we feel attacked or in a dangerous situation.

8. Gender-based response
The male and female responses differ to certain situat ions. It has been
noted that under stressful situations, males and females tend to act and
behave differently from each other, Hence their actions during fight and
flight response differs as well. For instance, if there is a certain stressful
situation, the males would be less likely to open up to someone about it
whereas females would prefer going to someone and talking it out.
Evolutionists’ view on the fight and flight response
Some researchers and evolutionary biologists believed that the sympathetic
nervous system of people belonging from the very early times of evolution
was quite active. Since there was a major goal of survival, and they had to
stay alert and be prepared for the fight or flight response all the time, their

9. sympathetic nervous system was almost all the time activated to ensure that
their body is prepared for the survival response at any given time.
If we look at the early evolutionary times, when man was still learning about
his surroundings, the fight or flight response was in a way th at they either
used to show aggression and confronted the threatening situation or they
would run away from the situation that felt life -threatening to them such as
identifying something a predator.
This is how the fight or flight response from the sympath etic nervous system
helped the people from the early evolutionary times.
In the current times, the fight and flight response has been modified in
action since now there is no basic goal of survival so there are other ways
we express the action of fight or flight response. Sometimes we express it by
talking loudly or getting in an argument whereas to express the flight
response we sometimes go quiet or start an addictive habit that might keep
us away from that stressful situation.
Homeostasis: Temperature regulation
The sympathetic nervous system is responsible for regulating the body
temperature hence maintaining a homeostasis balance in the body. Using
the fat reserves in the body and through the rush in the blood flow, the
sympathetic nervous system raises the body temperature as per
requirement. When needed, it brings it down to a cooler level through the
sweat glands.

10. Sometimes we experience our body getting heated up in an alarming
situation whereas sometimes our hands and feet feel cold when we are
encountered with a threatening situation.
This temperature regulation is done mainly by the sympathetic nervous
system.
Increasing the heart rate
The sympathetic nervous system is responsible for increasing the heart rate
when required by the body. In some situations like running or sitting down
when you are standing, there is a need to increase the heart rate to avoid
the situation of dizziness or faintness.
Whenever we encounter a threatening or alarming situation, we feel our
heartbeat suddenly getting increased, this is done mainly by the release of

11. certain hormones by the sympathetic nervous system. If there was no rush in
the heart rate, we would suddenly faint at the encounter of any such
alarming situation.
Parasympathetic nervous system
The parasympathetic division works as a counteraction to the sympathetic
nervous system. When the sympathetic nervous prepares the body for a fight
or flight response, the parasympathetic nervous system is responsible for
maintaining the normal bodily functions and bringing the body to its normal
and resting state once the body has encountered a certain alarming
situation.

12. When the body’s functions like a heartbeat or body temperature increases by
the sympathetic nervous system as a result of an alarming situation, the
body conditions need to be brought back to normal. This is done mainly by
the parasympathetic nervous system as it brings back the heartbeat,
temperature, and other body functions to normal.
Basically, the parasympathetic nervous system is there to make sure that the
body functions are continued as per normal like they usually function.
Location
The parasympathetic nervous system is situated near the brain and through
the long fibers, the parasympathetic nervous system extends to the
particular organs where the resting state is required, mainly the lung s,
bladder, stomach, and heart.

13. The nerves from the parasympathetic system arise from the sacral region of
the spinal cord.
Working of the system
Here we have discussed the basic aspects of the parasympathetic nervous
system that facilitates the normal wor king of the system
Fluid release
There are several ways through which the parasympathetic nervous system
ensures that there is enough fluid release at required places to continue
normal bodily functions.
When our eyes get dry due to a fight or flight respo nse or any given
situation, the parasympathetic nervous system makes the release of tears
available so that the eyes are lubricated to avoid being dried out.
The parasympathetic nervous system ensures the normal secretion of
salivary glands so that there are normal digestive operations after an upset
gastric event.
It also contracts the bladder so that there is normal urination after an
upsetting event.
Mainly the parasympathetic nervous system brings the body to its normal
functioning by controlling the secretions of certain glands. Several changes
are noticed in the body as a result of the action by the parasympathetic
nervous system. These changes can include :
• Normal release of saliva to improve digestion.

14. • Contraction of the bladder to promote normal flow of urination.
• Brings back the heart rate to normal after a spike in the heartbeat.
• Release of tears to avoid the drying out of eyes.
• Restores normal breathing by contracting the lungs region.
Roles and functions
There are certain roles and functions that are associated with the
parasympathetic nervous system as discussed below.
Rest and digest
The main function of the parasympathetic nervous system is the exac t
opposite of fight or flight response and that is rest and digest. The
parasympathetic nervous system is responsible for bringing the body back to
its normal functioning where it is at a state that is more at rest and all the
bold functions like digestion and heart rate have come back to normal.
In this way, the fight or flight response of the body is brought back to
normal by the rest and digest mechanism by regulating the gland secretion.

15. In other words, we can say that the parasympathetic nervous system can
also be referred to as the rest and diges t response of the body because this
is all the role that is performed by the PNS. After an emergency has passed,
the body comes back to normal regulation by the parasympathetic nervous
system.
To better understand the functions of the parasympathetic nervo us system a
popular acronym can be used here that is SLUDD.
SLUDD
This is a common acronym that completely covers the main roles and
functions associated with the parasympathetic nervous system. SLUDD
means:

16. • Salivation
• Lacrimation
• Urination
• Digestion
• Defecation
Let’s further discuss the roles and functions of the parasympathetic nervous
system based on this term.
Salivation
After we have experienced a rather dry mouth as a result of an upsetting or
alarming event, the parasympathetic nervous system acts on the salivary
glands to secrete more than usual saliva to ensure that the mouth is
lubricated enough for the normal eating and chewing functions of the body.
The parasympathetic nervous system achieves this by simply regulating the
secretions of the salivary glands that are present in the mouth. These glands
control the secretion of saliva in the mouth.
Lacrimation
After a stressful or alarming event, the eyes are usually dried out. The
parasympathetic nervous system ensures that there is enou gh flow of tears
in the eyes by the process of lacrimation so that the eyes won’t dry
themselves out.
If there are not enough tears in the eyes or if the eyes are not lubricated
enough, the eyes being a sensitive organ would dry out eventually. To avoid

17. this, the parasympathetic nervous system restores the normal functioning of
the eyes through the proper release of tears in the eyes.
Urination
The pelvic nerve originating from the spinal cord region is actually
responsible for the active flow of urination in the body after a fight or flight
response. When the body is unable to urinate properly after a stressful
event, the parasympathetic nervous system.
This is done by the contraction of the bladder. The parasympathetic nervous
system sends signals via the pelvic nerve which in turn contracts the bladder
leading to the normal flow of urination in the body.
Digestion
There are several ways through which the parasympathetic nervous system
brings the digestive operations back to normal. Firstly it stimulates th e
release of saliva which helps in the smooth flow and breakdown of food in
the mouth and the stomach.
The parasympathetic nervous system also stimulates the movement of the
stomach muscles more commonly known as peristalsis. This helps the food
moves faster and smoothly to the other organs for further digestion.
Other than these functions, the parasympathetic nervous system also
controls the release of bile. Bile is responsible for the normal digestion of
fats. Under stressful conditions, the body might re frain from the release of
bile hence the parasympathetic nervous system ensures the normal release
of bile for normal digestion of fats.

18. Defecation
The parasympathetic nervous system ensures that the movement of food is
right along the pathway of all organs so there would be normal bowel
movement when required.
Any unsettling event can hinder the normal bowel movement, this is brought
back to normal by the action of the parasympathetic nervous system on the
targeted organs.
Nerves associated with the PNS
There are some certain cranial nerves are associated with the
parasympathetic nervous system working to regulate the normal functioning
of the system including:
• The oculomotor nerve
• The facial nerve
• The glossopharyngeal nerve
• The vagus nerve

19. Difference between the sympathetic and parasympathetic
nervous system
Although the sympathetic and parasympathetic nervous systems are both
parts of the autonomic nervous system and work on the automatic or
involuntary actions of the body, there are differ ences in both systems that
make their functions opposite to each other.
Let’s discuss some of the major differences between the parasympathetic
and sympathetic nervous systems!
The pupil

20. The sympathetic nervous system: The pupil is dilated and enlarges whe n
there is any alarming or stressful event that requires the fight or flight
response by the sympathetic nervous system.
The parasympathetic nervous system: in contrast, the pupil comes back to
normal and it is constricted as it should be when the fight an d flight
response has passed and the body comes back to normal body function as a
response of the parasympathetic nervous system.
The Heart
The sympathetic nervous system: during a fight or flight response by the
sympathetic nervous system, the heart rate is suddenly increased. We feel a
sudden surge in the way the heart is beating making us breathe faster as
well.
The parasympathetic nervous system: After the stressful situation has
passed, the parasympathetic nervous system works to bring the heart rate
back to normal. When the heart rate is decreased to a normal level, it also
brings back the breathing to normal.
Lungs
The sympathetic nervous system: the lungs during a fight and flight response
by the sympathetic nervous system tend to dilate causing fast er breathing.
The parasympathetic nervous system: On the other hand, the lungs usually
come back to their normal resting state by the action of the parasympathetic
nervous system. This is done by the constricting of the lungs which leads to
normal breathing.

21. Blood flow
The sympathetic nervous system: when the body is encountered with a fight
or flight response, the sympathetic nervous system increases the flow of
blood to certain organs. In this way, we experience an increase in blood
pressure when we encounter an unwanted or unsettling event.
The parasympathetic nervous system: After the passing of the fight or flight
response, the parasympathetic nervous system comes into action to bring
the blood flow to all body organs to normal. Hence restoring the normal
blood pressure.
Digestive action
The sympathetic nervous system: as the body experiences any upsetting
event, the gland secretions slow down and ultimately it hinders the activity
of the digestive system.
The parasympathetic nervous system: After the fight or flight response is
over, the parasympathetic nervous system ensures the normal gland
secretion which in turn helps in bringing back the stomach activity and food
movement to normal.
Blood vessels
The sympathetic nervous system: The sympathetic nervous system is
responsible for constricting the blood vessels, this restricts the blood flow
activity, and increased pressure is required for the blood to flow hence
increasing the blood pressure.

22. The parasympathetic nervous system: when the parasympathetic system
comes into action, it dilates the blood vessels which helps to bring the blood
pressure back to normal.
Urinary output
The sympathetic nervous system: The sympathetic nervous relaxes the
urinary bladder and as a result of this, the body’s ability to pass the urine as
per normal is hindered.
The parasympathetic nervous system: when the body functions are to be
brought back to normal, the parasympathetic nervous system constricts the
urinary bladder and eases the flow of urine from the body hence increasing
the urine output.

23. Conclusion
The autonomic nervous system is the part of the nervous system that
regulates and controls the involuntary actions of the body. It is further
divided into two parts, the Sympathetic and parasympathetic nervous
systems. The sympathetic nervous system deals with the fight and flight
response of the body and develops alertness in response whereas the
parasympathetic nervous system brings the body back to its normal resting
state as it should be.
The study of the human nervous system is a vast and fascinating area to
explore. Learn about the in-depth aspects of the human nervous system
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