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- [Voiceover] Muscle tissue
comes in three different types.

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The first type to talk
about is skeletal muscle.

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Now skeletal muscle is growing muscles

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that are attached to your bone

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and muscles that move your body parts.

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So if you think, let's raise your hand

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or move your leg, those
are skeletal muscles

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performing that voluntary action.

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So if you are constantly
thinking about something,

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you want to do something, a movement,

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that movement that you can
do is a voluntary movement.

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Now these skeletal
muscles are multinucleate.

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That means they have
multiple nuclei per cell.

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That's kind of unique.

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Most cells have one nucleus.

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Well these skeletal muscles
are so large and so long,

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that they actually are multinucleate.

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Cardiac muscle, now
cardiac, you think heart.

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Cardiac muscle is the muscle of the heart

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that allows for the
contraction of the heart.

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Now if you find cardiac
muscle anywhere else,

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now you really shouldn't,

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because cardiac muscle
is only in the heart.

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Now cardiac muscle is involuntary.

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You cannot think heart
speed up, heart slow down.

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No, you can't do it.

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Sure, you can speed your
heart up by working out.

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You can slow your heart down
a little bit by relaxing.

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But can you just at instant
notice think, speed up?

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Doesn't work that way.

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So it's involuntary muscle.

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And they typically have a single nucleus.

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Then we have smooth muscle.

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Now smooth muscle surrounds
hollow structures.

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That's pretty vague and pretty general,

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because it's around a lot of things.

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You can think of any hollow
structures like your stomach,

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your small intestines, large intestines,

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a lot of your blood vessels,

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they're all going to contain
smooth muscle in the wall

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that'll help to contract and
move the substance through.

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Now you're thinking,
well, digestive tract,

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that's stomach and
intestines, cardiovascular,

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that's blood vessels,
they're all involuntary.

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You cannot control them.

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That means smooth and cardiac are both

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involuntary control mechanisms.

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And again, smooth muscle
has a single nucleus.

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So really, cardiac and
smooth share features

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of the involuntary.

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Skeletal, that's voluntary,
you can control those.

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So a little bit different that way.

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Here's a small micrograph picture

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of the skeletal muscle tissue.

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The one on the left, the
kind of purplish shape,

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is the actual view through the microscope.

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The one on the right is
the artist's rendition

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of what the view looks like.

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You can see how the muscle
cells are going left to right.

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They actually extend
beyond this field of view.

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So very long muscles, they
have very many nuclei,

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they're multinucleate.

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If you notice those little vertical lines,

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the ones that are going along
each individual muscle cell,

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kind of giving you a strip pattern,

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those are called striations.

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Now, those little tiny
lines are striations,

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they're made from the protein
that makes the actual cell.

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Here's cardiac muscle.

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It looks kind of similar.

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You still have those striations.

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But now we have these very
dark bands every so often.

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Those dark bands every so
often are intercalated discs.

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The intercalated disc is how
two cells are joined together,

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through your intercalated disc.

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Now also, if you notice,
there's a little more space

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in between the cells, that's
that little off-white area.

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So cells aren't quite packed as tightly.

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And here is smooth muscle.

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If you notice, smooth muscle
does not have any striations.

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All you're seeing is many little
cells all packed together.

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The cells are almost spindle-shaped.

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So tight little spindles,
or diamond shapes,

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they're kind of put together.

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They make sheets of muscle.

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These sheets are what wrap
around the hollow organ.

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So our skeletal, cardiac,
and smooth muscle,

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some views showing what they look like.

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The next category, the nervous tissue.

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The nervous tissue really
only has one primary cell,

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but then a whole lot of
secondary cell types.

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The primary cell is
going to be the neuron.

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The neuron is this specialized cell

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that actually generates
electrical impulses

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and then transmits that electical impulse

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to the next neuron or next tissue.

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These electrical impulses,

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these are our controlling mechanisms.

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When you think you want to raise your arm,

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or you want to move your leg,

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your brain, or spinal chord,

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are going to send these
electrical impulses

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down to the muscle.

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It's these electrical impulses

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that will stimulate the muscle to move.

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Well, the electrical impulses are also

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what allow you to think.

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All those thoughts,

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all the processes going on in your brain,

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are all electrical impulses.

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So, in general, a neuron
has three main parts.

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It has the structural components

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the body, dendrite, and axon.

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The cell body is where the nucleus is,

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it's more kind of a main
chunk of the actual neuron is.

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The dendrites and axons
are going to be protrusions

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or like branches coming off the cell body.

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The axon itself will carry information

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away from the cell body.

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The dendrite will bring
information toward the cell body.

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Because what happens to neurons is

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one neuron might connect or
synapse with another neuron.

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And you just sent information
from point A to point B.

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So that first neuron can
send information down

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from the cell body to the axon.

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Then that axon will give the information

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to the dendrite of the next neuron.

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So axons send information
away from the cell body,

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dendrites receive information

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and bring it towards the cell body.

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Now the secondary cells, they're not

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transmitting impulses,
they're not transmitting

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electrical impulses at all,
they're strictly support.

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The glial cells are meant to support.

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They come in many different sizes,

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many different shapes,
many different functions.

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Don't worry about all the
different parts and pieces.

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What we're focusing on is the fact

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that glial cells are there
to support the neuron,

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to keep the neuron healthy,
keep the neuron viable.

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Because once a neuron is killed off

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you may never get another
one to replace it.

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Neurons are pretty much there for life.

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So here's your micrograph
on the left-hand side,

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so you can see right
through your microscope,

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the very large purple
cell right in the mmiddle

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with all the protheses
or branches coming off,

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that is the neuron.

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The central core right there,
you can see the cell body,

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then you have an axon going up,

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and a whole bunch of dendrites

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going off to the side and down.

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All the little purplish
blackish dots around the neuron,

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those are all the glial cells,

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those are actually the
nuclei of the glial cells,

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but we can call them glial cells.

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Those are all there to support, to help,

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to protect that neuron, to
make sure it stays healthy,

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functional, and to make sure
everything is functioning 100%.

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If your neurons go down, your
nervous system goes down.

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So neurons are kind of important.