– A huge distinction between general senses
and special senses, special senses have almost specialized
anatomical structures that relay information,
that receive sensory information and deliver the information
to our sensory neuron. And then the sensory
neuron usually isn’t the one actually
receiving the stimuli so, for example, light comes in. The light activates a receptor, a specialized
anatomical structure that is sensitive to light. As soon as light hits it,
it activates. It sends the message
to this sensory neuron that then travels to the brain
and says, hey, that was a really
pretty thing I just looked at. Our first special
sensory structure is what enables us
to taste things. So, when you think of tasting
things, what do you think of? Your tongue.
And the sensory receptors found on your tongue are
your taste buds. Taste buds are my
sensory receptors. The word receptor is
a weird word because it actually
has multiple– there’s multiple things
that can qualify as a receptor. A taste bud. You think of the taste bud
as a little bump on your tongue, but it’s actually– a taste bud is embedded
in that bump, so I’m going to draw you a
picture. What? I really am. I know, I never
draw you pictures. This is your mouth.
It’s a space. If that’s your mouth– I should have made
this red so that you would know this your,
what? If it’s red.
That’s your tongue. And guess what these are?
They have to be pink. Oh, that’s a pretty color.
This– indeed it is so–
this is a taste bud. A taste bud is made up of
multiple special cells. They make up those
little, like, it’s really cool looking. They are cells so they
each have their own nuclei. There’s multiple cells in here. They’re all sensitive
to different things. This is actually a space.
This is called the taste pore. Since this is a space up here, this is actually
what kind of tissue? Yes, of course. Just having to pick
the perfect color. Maybe, oh, wow.
That was really hard do, but that’s a very lovely
color and it looks very nice. So what kind of tissue is this? What kind of tissue has
taste buds embedded in it? You know it’s epithelial tissue,
right, because here’s a space. So your tongue is lined
with epithelial tissue. If you had to take a wild guess,
what kind of epithelial tissue would you expect to
see on your tongue? You can push pause and
think about it if you want. Is there lots of diffusion
happening on your tongue? Should it be really
thin and thin? If it was really thin and thin,
it’d be broken, so what should we have there since I am talking
[gibberish] Like, my tongue would be falling
into a million pieces if it wasn’t lined with this
kind of epithelial tissue. Stratified– what?–
squamous, and when you look at i,
you’ll totally be like, dude, that’s so
stratified squamous, and it comes all the way down, and then we end up
with our little basal cells, you know, just
like you’d expect. And I don’t even have to tell you that it’s stratified
squamous epithelium. You totally could identify it.
In fact, we will in a second. So, the taste bud is not the somatic sensory
or the sensory neuron. Did you hear that?
It’s not– it synapses with the somatic
sensory neuron. So I’m going to draw
my neuron in here. And look, does this
sound familiar? I’m going to put a little,
like, I don’t know, footpad on here. A little sensory piece of
information saying, hey, if you had something to say,
you better say it to me. Who is this? This is a nerve
picking up taste. What nerves pick up taste? Oh, we’ll talk about
that in a second. I’ll try not to
get ahead of myself. Watch the magic. Here comes a piece of chocolate.
Mm-mm. Here comes a little
chocolate molecule. Yummy.
It goes in the taste pore. It binds with one of these cells that has a chocolate
molecule receptor on it. Like a little protein that
matches the chocolate molecule. This is so cool. And guess what happens
when they connect? This little cell says,
whoa, that was totally chocolate,
man. It tasted really yummy. And then, that’s when
a message gets sent to this little neuron which says,
oh, hey, we just picked up– there was a chemical that
bound to the receptor, caused a chemical reaction, and now I know that
that was chocolate, or, now I know I better send
the message to my brain so that my brain can
tell me what that was. And the message will get
sent through this nerve. Does that work for you?
It makes– it’s beautiful. It’s the chemical that
binds to the receptor, and the receptor sends the
message through the nerve, through the afferent nerve, to the brain where taste
is going to processed. Shall we talk about what
is going to be processed? Like, what’s the pathway? How do we get there?
Definitely. But first, there’s one more
thing I have to tell you. Guess what.
We labeled this as stratified squamous epithelium.
Of course we were right. That’s the kind of
tissue that it is. What’s the name
of the structure? Make sure for a quiz that
you’re cool with that. If I ask you– if I pointed to this,
what kind of tissue is this? You better say stratified
squamous epithelium. But if I say,
name this structure, you’re going to say, dude, that’s the
lingual epithelium. The lingual epithelium is made from stratified
squamous epithelium, but the lingual epithelium
is the structure itself. Within the lingual epithelium
is embedded the taste buds. The taste buds have
the taste pore that allows the chemical to come in.
Now let’s look at the nerve. Now let’s look at the pathway
your tongue has to follow. Your tongue doesn’t
follow a pathway. The pathway that the information that your tongue is collecting
follows to get to your brain. Great idea.
I’ll be right back.