Chapter 15: Nervous System

The NERVOUS System

(no, not that kind of nervous)

We mean THIS kind of “nervous!”

I think my urinary system

just functioned

#1 Review Review Review

Ask yourself, do you know how to describe:

•Homeostasis•Stimulus & Response•Structures•Functions

Maintaining internal balanceResponding to change/informationPartsJobs

#2 Nervous System OverviewOur friend Joe has suffered some real mishaps in his life…

*&@%#!

HELPME!

#3 Nervous System Overview, contd.

In all those events in Joe’s life, he counted on his nervous system tocome through for him…

Imagine if Joe touched the stove but had no clue that it was hot and left his arm on it for 20 seconds.

Imagine if Joe stepped on the nail and had no idea he was walkingaround with it for the rest of the day.

Imagine if Joe’s arm didn’t realize it had 4 canine teeth punctures in it and never decided to heal them up.

Imagine if he couldn’t see, hear or even smell that he’d wandered onto the 14 Freeway

#4 Nervous System Overview, contd.

But Joe’s body DOES do those things…and so much more, thanksto his brain!

talk

think

remember

touch

play

study laugh

dreamlearn

feel emotions

move

That’s a lot…and it’s so much of what makes us, well…

#5 Nervous System Overview, contd.

You can’t help but interact with your environment. You can feelhow uncomfortable your stool is, hear the hum of the air or heat when it comes on, smell the aroma of the last group that was in your classroom (ugh), and see hundreds of new images every second. Wow!

WOW

#6 Nervous System Overview, contd.

I hope by now the terms “homeostasis” and “stimulus : response” aren’tnew ideas to you.

Well, if any system is the king of homeostasis and the queen ofStimulus : response, then this is it!

Your brain and nerves (the nervous system) regulates most bodyfunctions & responds to the environment (through senses).

This is it. The human brain. About thesize of your fists put together, it stores everything you have known or ever willknow. Weird, when you think about it.

#7 FUNCTIONS of the Nervous System

1. Maintains homeostasis using all other body systems

Nervous System

circulatory

respiratory

skeletal

muscular

integumentary

digestive

urinary

any others

2. Uses nerves to process stimuli and carry out responses

Like a super-busy telephone switchboard, your brain uses nerves (think: wires of the body) to receive and send signals CONSTANTLY.

#8 STRUCTURES of the Nervous System

Let’s start small and work our way bigger…nerves (think of them like wires) are actually special support cells and other nerve cells called neurons. Neurons are VERY unique. Let’s see some ways:

•In regards to cells, neurons can be huge…they can be wide enoughin diameter to be seen without a microscope, and some are almost3 feet long!

Thick nerves seen here are bundles of individual neurons.

#9 Structures, contd.

•Neurons aren’t programmed to die like your other body cells…the neurons you were born with are the same ones you’ll have when you’re 89 years old. Very few are made after the age of about two.

•Using ions (electrically chargedatoms), neurons are able to passsignals down their very longtails (axons) at more than the lengthof a football field per second. Yeah—they’re fast. And weird looking. (axon)

(dendrites)

(cell body)

#10 Structures, contd.

We’ll talk about two main kinds of neurons…those that are going TO thebrain, and those that are leaving FROM the brain.

a. sensory neurons – send signals to brain from senses

The smell of freshly-baked muffins, the soft fur of a kitten against your cheek, how hot you are after running 4 laps on the track…all of these sensory signals are logical to you only because the brain processes the information sent to it by nerves.

#11 Structures, contd.

So your sensory neurons have sent signals telling your brain that you:•Need to get up off the cactus you just sat on•Need to raise your left hand to catch the softball•Need to plug your ears because the cannon is about to be fired

…how do you actually go about DOING those things?

It’s all thanks to your: (b.) motor neurons – send signals from brain to muscles or organs

#12 Structures, contd.

So, a sensory neuron sends a signal to your brain, your brain processesit, and it then might send a signal down a motor neuron to a muscle torespond. But sometimes you need this to all happen super-fast!

A (c.) reflex is a quick, automatic reaction caused by sensory & motorneurons skipping the brain. This reflex

doesn’t involveany “thinking”of your brain.

See…your sensory neurons send signals to yourspinal cord, which is “smart” enough to respondimmediately (without wasting time asking forpermission to the brain) and uses your motorneuron to jerk your leg up.

#13 Structures, contd.If you ever hear of scientists/doctors referring to the CNS, they’re talkingabout the Central Nervous System. The CNS consists of the brain & spinal cord. It’s the “thinking” & “control” part of your nervous system.

In the diagram onthe right, you’llsee that your other nerves (both sensory and motor neurons) everywhere else are called the “peripheral” nervous system.

#14 Structures, contd.

Ok, this is it. The…I mean…THE boss organ of your body. This isthe ultimate ruler of your whole self. People have marveled over itfor thousands of years and we learn more of how it works every dayit seems.

weird looking

As far as thebrain goes, we’lljust worry aboutits 3 main parts.

For now, please justremember this: your brainis NOT a muscle. It’snerve cells!

#15 Structures, contd.In the blank part of your notes page, let’s sketch a simple brain. It’snot difficult. First, do a basic outline which is sort of like a mitten.

Now add in some of thefolds (which show howtightly packed your brain isinside your skull).

Perfect…now label thissection “1”.

1.

This huge section is the (1.) cerebrum – it controls movement, senses, memory, thinking. It’s the source of your emotions, too. Wow. Think about how God made this incredible lump of cells. Seriously, give it some thought. Simply amazing.

#16 Structures, contd.Let’s add in a new section: Draw in a blob at the

bottom right.

Make it stripey.Label it “2”.

2.

2. cerebellum – this part of the brain coordinates your muscles andbalance. If you stand up, think of all the dozens of tiny muscularcontractions your thigh, foot, calf, etc. muscles have to do every second to correct your slight teetering to one side or the other. Yourcerebellum makes it happen.

#17 Structures, contd.Draw this:

3.

This widened section of the spinal cord near whereit joins your brain is called the (3.) brain stem – it THANKFULLY controls yourinvoluntary life functions, ex: breathing, heartbeat

Imagine if the medulla failed. Yikes!

#18 Structures, contd.

As far as the spinal cord goes, it can do a little thinking on its own,which is why its considered a part of the CNS, but its main job is tocarry messages to and from the brain.

You already know how important it is that your vertebrae successfullyprotect your spinal cord. If not, it can be injured permanently, withlittle or no chance at recovery.

actor Christopher Reeve before and after his tragic horse-riding accident

#19 DISORDERS of the Nervous SystemWell, there are so many to choose from that

affect your brain and/or nerves. Here’s justa few.

(ouch for this guy)

Same guy, afew minuteslater.

Fortunately, hedidn’t suffer anylong-term paralysis, but heDID have a concussion.

(1.) A concussion happens when the skull slams into the brain, “shocking” it. This happens whenthe brain sits still due to inertia, but a collision moves the skull into the brain very quickly.

#20 Disorders, contd.Here’s a truly sad and tragic one. As some people age, their brain cellsstop communicating with each other, causing memory loss. This isknown as (2.) Alzheimer’s Disease (not “old timer’s disease”).

This almost always is found in elderly people, and the cause is not Really well-understood. There is no cure, and the only treatment seems to be the patience and understanding of the sufferer’s loved ones.

Imagine leaving the house and not remembering why you left in thefirst place, then forgetting which house was yours, and simply feelingtotally, helplessly lost. Imagine opening your eyes from a nap andnot having a clue who your own daughter or husband were as theysat next to you. Hopefully, someday there will be a cure for this.

President Reagan and Charlton Hestonboth suffered from Alzheimer’s.

#21 Disorders, contd.

Imagine your hand shaking uncontrollably…eating with a fork ortying your shoes is so frustrating and uncomfortable…and embarrassing.Eventually you have a hard time making your mouth and tongue formthe sounds of words you’re trying to speak. This is the effects of (3.)Parkinson’s Disease.

This is a disease caused by brain damage that causes loss of muscularcontrol & coordination.

Michael J. Fox andMuhammad Ali.

#22 Disorders, contd.

If a blood clot blocks some areas of the brain from getting oxygen,those cells die. Well, they’re not replaced, so whatever those cells used to control will likely suffer from limited or non-function.

This is a (4.) stroke – clot in a brain blood vessel…can cause death ofbrain tissue.Strokes are very serious, and can definitely be life threatening. People who survive strokes may have one side of their face “droop”since they can’t control the muscles there anymore.

#23 ReviewSo, could you live without this system? La dee da

dee dum…

If Joe’s brain “stopped” or “disappeared”he wouldfall dead instantly.

#24 Review, contd.

What does the Nervous System do for homeostasis?

ALL it does IS homeostasis! That’s all it does, all day all night!

AND the same goes for Stimulus : Response. Your brain isCONSTANTLY processing signals…so much so that it causes youto flush some of those things out or re-visit them in your dreams!

#25 Review, contd.

You really only get one brain. There’s no brain “transplant” either.When you kill those brain cells, they don’t magically repair them-selves, usually. So TAKE CARE OF IT! Think of Ozzy!

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Stay off the drugs, kids! LsdkalDsklsjdj djannd ehenan engnaEnnq ueueusn dndns andooop

Sndnda ndnnnnngggnn

#26 And That’s…

Answer the following questions on a sheet of notebook paper.

1. What are the three main functions of a nervous system?2. What structures comprise the Central Nervous System (CNS)?3. What are sensor neurons?4. What are motor neurons?5. Sensory and motor neurons are collectively called the

______________________.6. The structural and functional unit of the nervous system is the

___________________.7. What is a reflex?8. What are the 3 main parts of the brain and their functions?9. What is the main function of the spinal cord?10. What happens to the brain when you get a concussion?11. How are strokes caused?12. Nerve cells are also called?