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- [Voiceover] As we're finishing up

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this section on the
central nervous system,

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we need to look at some drug interactions

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and some disorders.

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Now, psychoactive drugs,

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what they're actually doing

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is affecting your state of consciousness,

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emotions, behaviors,
because they're interacting

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with the neurons and cause the neurons

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to either fire faster, to fire slower,

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or to completely misfire
creating different perception.

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Now the reason they're active is they can

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actually go across the
blood brain barrier.

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Now, these higher brain functions

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that are affected can be
anywhere from perception

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of reality to balance to
emotion to anything really

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in the brain can be affected.

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So as they change the way
that the actual neurons

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are working, they're dealing with how

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the neuron transmitters
are being released.

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By releasing more neurotransmitter

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you can actually cause an
increased reaction of neurons,

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or releasing less neurotransmitter.

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They might even completely
stop neurotransmitter activity.

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So it all depends on which
ones are being affected,

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which neurotransmitters that is,

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and how they're affected,

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as far as what will make a difference

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in your consciousness, your emotions,

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or your behavior, or all three together.

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Now these psychoactive drugs

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can cause psychological dependence.

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A lot of times after using,

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the users will crave that feeling again.

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They'll want to go back to
wherever that place was,

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or whatever that feeling was.

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The problem is then once
they start doing that

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they start to build up a tolerance.

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So to be able to achieve
the same level of feeling,

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they have to increase more and
more of the drug each time.

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And by continually increasing
the amount of drug,

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all they're doing is maintaining

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the same psychoactive feeling.

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Problem is your body will not stop.

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The tolerance keeps building,

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you keep having to put more
and more into the system.

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Now this is pretty much
your common addiction.

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It's the person need, a
physiological or psychological

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aspect, their need to use a substance.

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Maybe you're saying that,
you don't take drugs,

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so you're saying "Okay,
fine, never had problems,

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"I don't know anyone that
has a problem with this.

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"So it's a choice, why
not make a free choice?"

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Well it's not really a free choice.

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The person's body is screaming at them

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to have more of this psychoactive drug.

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To go back to that same feeling.

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Some of the physiological
reasons sometimes

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is certain drugs start to
replace neurotransmitters.

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So without the drug in the system

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the person's actually having fewer

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neurotransmitters than normal.

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By using the drug, they're just going back

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to a normal state of nervous activity.

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Well, in cases like that
it's not really a choice.

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Without using it the body's
not functioning properly.

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Now are there ways to reduce
or eliminate addiction?

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Sure, there's different treatments,

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different medications,
different types of methods

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that could help out.

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But for pretty much any addiction

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the person that's addicted
must want to do it.

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Doesn't matter how many people tell them,

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how many people are
showing them the problems,

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if they truly don't
want to go off the drug,

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no course of treatment is gonna help.

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And under any time they're
getting off addiction,

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withdrawing, the physical symptoms

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can range from mild,
maybe a little discomfort,

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a little nausea, to
extreme, complete vertigo,

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cold sweats, fevers, wracking chills

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throughout the body.

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So there can be some very minor

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to very major withdrawal effects.

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It depends on how much the
drug the person was used to

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and what drug it is.

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To start off our disorders
we're looking at trauma.

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Now, trauma's a pretty general term.

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It's any physical injury to
the brain or spinal cord.

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One type is a concussion.

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In a case of a concussion,
it says your blow

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to the head may lead to
unconsciousness, true

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but this blow to the head
could be from a blunt object,

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like a baseball bat, could
be a sharp impeding blow

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from a knife.

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But any impact to the
head that causes damage

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could result in concussion.

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So besides the fact of
being knocked unconscious

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you might have a disruption
in the electrical activity

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of the brain.

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Well if you disrupt electrical activity,

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that means your memory
might also be affected.

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So even if you weren't
rendered unconscious,

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you're still conscious looking around,

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10, 20 minutes later you might look back

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and say "I have no idea what happened

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"for these five minutes."

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Just completely blank in your mind.

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There also is the risk
of a subdural hematoma.

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Subdural hematoma is a build up of blood

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under the durma, so in the subdural space.

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Now this subdural hematoma
could be very dangerous

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because it could apply
excess pressure to the brain.

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Now does every impact to the head

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cause a concussion?

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No, does every concussion
knock a person unconscious?

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No, so there's varying degrees

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from very mild to very severe concussions.

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Moving down to the spinal cord,

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there's different spinal cord injuries.

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So if you have an injury
in the spinal cord,

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if you have an impairment,

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if you have a pinching, a severing,

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well anything that's below that point,

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so for example, there's an
injury in the thoracic region

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of the spinal cord.

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That's right where your rib cage is.

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That would mean that you potentially might

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have enough of an
impairment where you lose

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all sensation and
function below that point.

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That means your hips,
your waist, your legs

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would not respond, they
would not be functional.

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So spinal cord injuries,
brain injuries, concussions

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all are pretty severe
injuries and problems.

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But how 'bout the infections?

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Well we could look at
a virus or a bacteria,

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all depends on what is
actually being affected.

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In the case of encephalitis
this is a viral

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infection causing
inflammation of the brain.

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Now in a new born it's
not quite as problematic

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but in an adult, could
be very problematic.

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The difference is in a new born,

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their skull is not held together yet.

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So an increase in pressure or inflammation

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would simply push the
bones of the skull outward.

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Where in the case of an adult,

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those bones are solid,
you're not pushing them out.

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So if inflammation occurs,
if you can't push out

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that means you're pushing in.

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Into the brain.

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Meningitis, now this is inflammation

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of the meninges around the brain

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or sometimes the spinal cord.

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Remember the meninges
are those three layers

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of connective tissue.

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So we're trying to protect the brain

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but can also cause an
infection of the brain.

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Now it could be viral meningitis

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or it could be bacterial meningitis.

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Rabies, lot of times you think of rabies

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as an infected animal.

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Well that's what spreads it.

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But this is a viral disease.

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It can spread from the
bite of anything infected,

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an infected animal, could
be a person that is infected

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and it'll travel from that infected bite

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up to the brain.

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It travels through these sensory neurons

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what's carrying the
information back to the brain.

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So, rabies viral infection
that is heading to your brain

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once it enters the system.

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Then we have brain tumors.

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Now brain tumors could be
benign, without cancer,

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or they could be cancerous.

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But in general a brain tumor
is any abnormal growth,

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anything that's growing unusually

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and usually when something in the brain

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is growing abnormally,
it's putting pressure

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on something that shouldn't be pushed.

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So if all it's doing is putting pressure

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on the wrong spots,
whatever is being forced

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or pressured could potentially
lose it's functionality.

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Some more disorders, epilepsy.

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Now in epilepsy it's usually a recurring

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episode of unusual or
abnormal electrical activity.

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It's a fancy way of
saying recurring seizures.

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Alzheimer's disease, in
the case of Alzheimer's

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the patient does not have
enough acetylcholine.

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So what ends up happening

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is we end up accumulating
some abnormal proteins,

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we have more progressive memory lapses,

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dementia kicks in.

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The person just really has a problem

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processing, understanding,
and remembering information.

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All because that
neurotransmitter acetylcholine

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isn't in high enough quantities.

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Parkinson's, well in
the case of Parkinson's

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you're losing your
dopamine releasing neurons.

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Now dopamine is gonna be a
type of neurotransmitter.

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What ends up happening
in Parkinson's disease

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is you slowly and continually degenerate

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any of the motor activities.

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So this is gonna cause
problems with movement,

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gonna cause problems
with control of limbs.

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So Parkinson's disease, do you know what?

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Dopamine causing the problem.

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So here we have a nice brain image.

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The one on the left, A,
nice healthy brain scan.

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The one, the B, is showing
Alzheimer's disease.

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Can you notice there's a
lot more blue and black

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in the Alzheimer's
disease's patient's scan.

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Well that means there's less activity,

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less functioning inside that brain.

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Less functioning, well that means

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that is not simply able to
process as much as efficiently.

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So the healthy on the left, the letter A,

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Alzheimer's on the right,
not as much functional

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patterns in the brain.