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By the end of this section, you will be able to:
  • Describe the difference between the central and peripheral nervous systems
  • Explain the difference between the somatic and autonomic nervous systems
  • Differentiate between the sympathetic and parasympathetic divisions of the autonomic nervous system

The nervous system can be divided into two major subdivisions: the central nervous system (CNS)    and the peripheral nervous system (PNS)    , shown in [link] . The CNS is comprised of the brain and spinal cord; the PNS connects the CNS to the rest of the body. In this section, we focus on the peripheral nervous system; later, we look at the brain and spinal cord.

Image (a) shows an outline of a human body with the brain and spinal cord illustrated. Image (b) shows an outline of a human body with a network of nerves depicted.
The nervous system is divided into two major parts: (a) the Central Nervous System and (b) the Peripheral Nervous System.

Peripheral nervous system

The peripheral nervous system is made up of thick bundles of axons, called nerves, carrying messages back and forth between the CNS and the muscles, organs, and senses in the periphery of the body (i.e., everything outside the CNS). The PNS has two major subdivisions: the somatic nervous system and the autonomic nervous system.

The somatic nervous system    is associated with activities traditionally thought of as conscious or voluntary. It is involved in the relay of sensory and motor information to and from the CNS; therefore, it consists of motor neurons and sensory neurons. Motor neurons, carrying instructions from the CNS to the muscles, are efferent fibers (efferent means “moving away from”). Sensory neurons, carrying sensory information to the CNS, are afferent fibers (afferent means “moving toward”). Each nerve is basically a two-way superhighway, containing thousands of axons, both efferent and afferent.

The autonomic nervous system    controls our internal organs and glands and is generally considered to be outside the realm of voluntary control. It can be further subdivided into the sympathetic and parasympathetic divisions ( [link] ). The sympathetic nervous system    is involved in preparing the body for stress-related activities; the parasympathetic nervous system    is associated with returning the body to routine, day-to-day operations. The two systems have complementary functions, operating in tandem to maintain the body’s homeostasis. Homeostasis is a state of equilibrium, in which biological conditions (such as body temperature) are maintained at optimal levels.

A diagram of a human body lists the different functions of the sympathetic and parasympathetic nervous system. The parasympathetic system can constrict pupils, stimulate salivation, slow heart rate, constrict bronchi, stimulate digestion, stimulate bile secretion, and cause the bladder to contract. The sympathetic nervous system can dilate pupils, inhibit salivation, increase heart rate, dilate bronchi, inhibit digestion, stimulate the breakdown of glycogen, stimulate secretion of adrenaline and noradrenaline, and inhibit contraction of the bladder.
The sympathetic and parasympathetic divisions of the autonomic nervous system have the opposite effects on various systems.

The sympathetic nervous system is activated when we are faced with stressful or high-arousal situations. The activity of this system was adaptive for our ancestors, increasing their chances of survival. Imagine, for example, that one of our early ancestors, out hunting small game, suddenly disturbs a large bear with her cubs. At that moment, his body undergoes a series of changes—a direct function of sympathetic activation—preparing him to face the threat. His pupils dilate, his heart rate and blood pressure increase, his bladder relaxes, his liver releases glucose, and adrenaline surges into his bloodstream. This constellation of physiological changes, known as the fight or flight response    , allows the body access to energy reserves and heightened sensory capacity so that it might fight off a threat or run away to safety.

While it is clear that such a response would be critical for survival for our ancestors, who lived in a world full of real physical threats, many of the high-arousal situations we face in the modern world are more psychological in nature. For example, think about how you feel when you have to stand up and give a presentation in front of a roomful of people, or right before taking a big test. You are in no real physical danger in those situations, and yet you have evolved to respond to any perceived threat with the fight or flight response. This kind of response is not nearly as adaptive in the modern world; in fact, we suffer negative health consequences when faced constantly with psychological threats that we can neither fight nor flee. Recent research suggests that an increase in susceptibility to heart disease (Chandola, Brunner,&Marmot, 2006) and impaired function of the immune system (Glaser&Kiecolt-Glaser, 2005) are among the many negative consequences of persistent and repeated exposure to stressful situations.

Once the threat has been resolved, the parasympathetic nervous system takes over and returns bodily functions to a relaxed state. Our hunter’s heart rate and blood pressure return to normal, his pupils constrict, he regains control of his bladder, and the liver begins to store glucose in the form of glycogen for future use. These processes are associated with activation of the parasympathetic nervous system.

Summary

The brain and spinal cord make up the central nervous system. The peripheral nervous system is comprised of the somatic and autonomic nervous systems. The somatic nervous system transmits sensory and motor signals to and from the central nervous system. The autonomic nervous system controls the function of our organs and glands, and can be divided into the sympathetic and parasympathetic divisions. Sympathetic activation prepares us for fight or flight, while parasympathetic activation is associated with normal functioning under relaxed conditions.

Personal application questions

Hopefully, you do not face real physical threats from potential predators on a daily basis. However, you probably have your fair share of stress. What situations are your most common sources of stress? What can you do to try to minimize the negative consequences of these particular stressors in your life?

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Questions & Answers

Do you have a pdf available for this content?
Ancil Reply
do you have a pdf of this content?
Ancil
For which?
vidhyalakshmi
stress,coping and wellbeing
Ancil
you can google it, you'll find plenty
Priyank
but i felt contents in this app is awesome , that's why i was looking for the pdf contents of this app
Ancil
Ypp I too feel the content useful
Sakshi
what is creative thinking
Ayesha Reply
The thinking process where you are able to project a clutter of ideas and streamline them into concepts that either appeal to or meet the specifications of the target end product of what that thinking process is applied for
Neo
creative thinking could be thinking outside the box, going against the grain sort of speaking.
vincent
Creative thinking is a new way or method in reaching the target which none has used until that particular moment.It is always attractive and easy to reach next levels.And the point is not all people get this sort of thinking.
vidhyalakshmi
What is the difference between drive and motivation?
Shanice Reply
who would give a psychopath and a sociopath meth amphetamine ( exampels)-louise otero and Sylvia myers
Shawnasie
drive is like a commitment to follow through and motivation is kinda like the desire to follow through.. both together would bring a desire to follow through I suppose
Alexis
Drive is that feeling/reason for the desire to do something, while motivation is that thing which keeps your drive going. Motivation pushes you to achieve what drives you. Drive is the answer for 'how do you do this' while motivation is that catalyst that helps you complete what you started.
Kavya
Why wasn't Carl Jung discussed within the context of historical ( introduction to) psychology?
Dr Reply
What are the symptoms of acute stress?
Shanice Reply
Lose interest in the things that you like to do (for example you like to read or watch movie but when you have acute stress those things don't excite you anymore), feeling tired all day, insomnia / hypersomnia.. and the symptoms has last for quite some time.
Kelly
There are more symptoms but I can't remember it right now
Kelly
Is weight loss one of them ?
Shanice
yeah but you also have to take in consideration as well you may want to think about the full word or question being discussed or asked, starting with the word Acute, so maybe size it levels of stress present are a main focus when answering or giving optional input so yes i agree
Kayla
weight loss or gain it can go both ways ( my personal experience) and it is often hard to break the chain to change back to health level
altug
Okay, thanks.
Shanice
how can we practice personality psychology?
Nasra
what's the captive psychology?
ghada
guys you are really mean, you don't even want to at least try to help me. 😢😢😢😢😭😭I thought you were awesome
Nasra
ow
Maxamed
define human emotions and types of emotions
Chukwuede Reply
sorry I hit send to many times
vincent
human emotions are your feelings like angry sad happy etc
latosha
emotion is a personal conscious experience.
bett
I don't understand sensation and perception 😩
Shanice Reply
Sensation - detection of basic stimuli (light coming into eyes) Perception - way we interpret the detected stimuli (seeing colours)
Marcel
I second you marcel
Sachin
how can I learn behaviorism
Brent Reply
***youtu.be/NNnIGh9g6fA
Waskar
Any other methods to manage stress ? And Thank You !
Charbel Reply
Any idea about new ways to manage stress ? And Thank You !
Charbel
I'd like to manage my stress better too how thou?
Shawnasie
a wide array of copping mechanisms that you could alternate between would be my best guess
Shawnasie
I guess, managing stress is not that difficult. When you get some sort of stress, make a pause and leave the place for a while.Get some fresh air,some happy songs,make a convo with your best friend,eat as much as you want,and the best way is to take a nap. :)
vidhyalakshmi
Common symptoms of major depressive disorder include all of the following except......
EDNSAGAR Reply
how many stages do people go through in life and what are their names
Stanley Reply
3 stages: adolescent, youth, old
Komal
what about infant, toddler, pre-school, adolescent, young adult, middle age and elderly?
Kathy
anagen , catagen, telogen. or is that just for hair growth only?
Carrie
you should look up Freud and Erikson stages
vincent
good answer Vincent.
Kathy
so much to learn in psych.
Kathy
thank you :)
vincent
Hi
zahir
Guys how are you?
zahir
Let's talk about abnormal psychology?
zahir
I need to understand lot about what
zahir
hi
Tasfia
Abnormal psyh is a huge undertaking...you should take some classes. You could be in school for years, there is so much to learn. I took psych in nursing school and did clinical at a now closed psych institution...and I loved it. The human condition is amazing.
Kathy
Abnormal psych is a great major.
Kathy
Thanks. That's what i need to learn all about behavior. Human beings. Nervous and whats happen in the brain
zahir
I tray to be good for all of those stuff
zahir
What is this chat about
Elise
Take intro to psych to see if you enjoy it!
Kathy
infant, child, adolescent, young adult, middle adult, and old adult
Steffenney
Why does anxiety show up alarmingly fast for some people but others show little signs of it?
Elise Reply
why does this app have chat
Callum
It is more of a discussion.
Elise
a forum then
Callum
I guess so.
Elise
anxiety stops people from participating so seeing signs of it is usually difficult is it not?
Callum
it's pretty epic
juan
is there an app for psychophysiology?
juan
Not sure what you mean by participating but what I was meaning was anxiety affects others dramatically while some others don't even have anxiety and I was wondering why that occurs.
Elise
by participation i meant anxiety causes fear to move outside your comfort zone or even some activities within it.
Callum
so your question is why do some people have anxiety and some don't?
Callum
I guess so.
Elise
It depends on a person's lifestyle and how the people surrounding them are and the person's mentality
Kevin
I'm not a psychologist I'm an occupational therapists but I'd assume it's a mixture of genetics, environmental factors and development.
Callum
as kevin said
Callum
Right on spot :)
Kevin
It might be because of the natural disposition and personality traits. suppose, if someone is open to new experiences they might not find a new situation challenging enough while on the other hand a person not open to ideas and experience might find himself/herself in a tight corner worrying.
Simran
That is what I thought as well. I have just recently been asked a lot about anxiety and I didnt want to misinforming
Elise
I think it has to do with the way brain is wired for each. some have to build resistance to anxiety whereas others already have a higher resistance to anxiety.
vincent
I struggle with Anxiety very severe. And I don't really know what to do to help get rid of it..
Aryana
anxiety is an elusive but powerful mental problem, it would definitely be intersting to look into it more
Callum
hmmm
Aryana
Anxiety is something that is hard to handle at points. If it gets hard to handle best thing is professional help.
Elise
The best methods i have seen to beat anxiety, i do suffer from it myself, is exposure therapy where you put yourself into those difficult situations like talking to strangers that kind of thing and just working your way through experience
Callum
Well my anxiety is pretty difficult to do that, I get super red when I like get anxiety attacks and other things with it
Aryana
I recommend tai chi or the 1 2 3 breathing exercises
vincent
Also many don't experience anxiety like I do but it will come on randomly and thr best thing to do is breathe.
Elise
yea i can imagine that is why it would have to be in some kind of safe place where you can escape or relax if needed.
Callum
what is tai chi? And yeah I usually do just turn the other way and breathe but still it hits hard
Aryana
there can be multiple reasons behind it. it can also be subjected to sufficient and necessary causes. There can be number of incidents that could have made a person anxious in the past and that has piled up and even similar issue ahead can manifest a lot of reaction and anxiety in future.
Simran
breathing exercises are definitely important too yea
Callum
Yeah thank you
Aryana
Best thing is to just breathe and remember to be relaxed
Elise
if youre not already you should definitely seek seeing someone about it. idk where you guys live but in NZ we get 10 free sessions
Callum
Talking to a professional will help you understand and receive treatment.
Elise
Yeah, I've been watching to go talk to someone but I can't being myself to get the courage to talk about this
Aryana
There might be an underlying cause behind it and a professional can help you to understand the cause of it and how to break through your inhibitions. You can try out progressive muscle relaxation exercises as well, it will help in calming you down and benefits are way too much there.
Simran
well you can talk here this seems like a reasonably safe place but i would encourage you try to see someone, maybe take a family member, friend for support
Callum
It will be best for physical and emotional health
Elise
Yeah I agree, but sometimes I can't even talk to a family member or friend because I feel like I'm being judged or something but that just comes with the problem
Aryana
i used to feel like that but there is no shame for asking for help and they should support you if want to get better.
Callum
I know how that feels. You will have to accept that you need the help. It may take a while.
Elise
Yeah
Aryana
I honestly wouldn't mind Anxiety if it didn't show in my face and if I didn't have panic attacks
Aryana
well yea the symptoms can be very distressing because as i said before it will stop you from participating in things like social interactions
Callum
Anxiety isn't just caused by social interactions
Elise
Yeah it will, I do online school now because of it..
Aryana
Good day to everyone
Ayomide
ah really, that is very drastic. definitely seek a professional when you can
Callum
good day David
Callum
Thank you
Aryana
It will be hard
Elise
I know its gonna be rough but I'm over it, I'm ready to start living my life again
Aryana
Good thinking
Elise
for sure thats the right attitude Aryana!
Callum
Thank you all very much
Aryana
best of luck
Callum
I think everyone feels Anxiety but degree variates.And when it is out of control person suffers psychologically n physically too.Then symptoms can be observed.To come out or deal with it.One can consult professional help if required or can start with small steps.Like to remember ones strengths etc.
anuradha
may be because of their living standards and surroundings.If they have already experienced they will not show fast anxiety
Anis
perception..... no?
juan
I think....so
Anis
That is personal belief.
Elise
no.
juan
It depends on how someone sees anxiety.
Elise
depression &substance use
Shawnasie
it has a co acerance in both up to 60%
Shawnasie
Diagnosed anxiety along with depression are apart of post traumatic stress disorder previously known as shell shock... now "shock" often comes on instantly, hence the name. A natural reaction to a specific chemical imbalance, Like when people are extremely happy, sad or sometimes even angry they cry
Luci
how can we treat multiple personal disorder
dilpu Reply
We must have to take help of a counselor or therapist.We can treat but upto some points only
Anis
The best we can do is support them. The rest is up to the counselor.
shri
have you ever read the biology of belief?
juan
***youtu.be/82ShSNuru6c
juan
Best thing is to be there for the person and make sure you show support but really only a professional can do much more to help.
Elise
Bruce Lipton seems quite brilliant
juan
I believe all you need is a shift in perception....
juan
we have to know & work first on root reason from where all these started
Anis
perception
juan
you were not born with the diagnosis; just a perception phenomena
juan
classical conditioning
Its Reply
what is psychology
Sohdip Reply
the science of psychic
Horia
It is a scientific study of human mind and behavior. Encompasses a lot of domains.
Simran
the study of the human mind and the way soceity effects it.
Doctor
thanks
Sohdip
psychology is dealing with society and the mind and everyday living
Gloria
dealing with mind, behaviour and thought of humans
Anis
It is understanding your mind and others mind and the chance of behaviour accordingly.
vidhyalakshmi

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Source:  OpenStax, Psychology. OpenStax CNX. Feb 03, 2015 Download for free at https://legacy.cnx.org/content/col11629/1.5
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