Video Transcript
In this video, we will investigate
the principles of hormonal control by exploring the structure and function of the
human endocrine system. Then, we’ll try some practice
questions together. And finally, we’ll review what
we’ve learned. So, let’s make like the pituitary
gland during puberty and get started.
Your endocrine system is one of
about 11 organ systems that work together in a set of closely integrated
interactions that carry out your life functions. Your endocrine system works closely
with your nervous system to perform the essential function of control and
integration of the other body systems.
The endocrine system plays its role
in control and integration through the action of hormones. Hormones are chemical messengers
that carry signals throughout your body. They are special molecules produced
by your endocrine glands. Here’s a diagram of some of the
major glands of your endocrine system. Here we have the pituitary glands,
the thyroid, your adrenal glands, the pancreas, and the gonads — ovaries in females
and testes in males. Each of your endocrine glands
produces one or more hormones. And you’ll notice that the glands
are scattered throughout your body. They don’t need to be clustered
together like other organ systems because the glands secrete hormones, which are
then carried in the bloodstream until they’re transported to their target cells. The target cells are the specific
cells that bear receptor for or react to a specific hormone.
So, we’ve learned that your
endocrine system consists of glands, which secrete hormones, which are then
transported by your circulatory system to the target cells in the tissues and organs
upon which they act. Next, let’s take a closer look at
some of these glands, their hormones, and their actions.
This diagram shows a cross section
of your brain. And here at the base of your brain
nestled deep within your skull is the pituitary gland. The pituitary gland is very small,
about the size of a green pea. But it’s often referred to as the
master gland because it controls the actions of many other glands within your
endocrine system. It produces many hormones, which
generally act to stimulate other glands. The pituitary gland is well known
for producing growth hormone, which, among other things, stimulates growth. That’s especially apparent during
the growth spur experienced during puberty.
The next gland we’ll look at is
your thyroid gland. The thyroid is located in your neck
wrapped around your trachea. If you place your hand against your
neck and swallow, you’ll feel a piece of cartilage move up and down. Your thyroid gland is located just
below that piece of cartilage. The thyroid gland produces the
hormone thyroxine, which is responsible for regulation of your metabolism. This means that your thyroid gland
affects weight maintenance and energy levels.
The next gland we’ll look at are
your adrenal glands. Each of us has two adrenal
glands. And they sit on top of our kidneys
like little hats. In fact, ad- is a prefix meaning
near. And renal is a word that means
kidneys. The adrenal glands most famously
produce a hormone known as adrenaline. A large quantity of adrenaline
released into the bloodstream can trigger something called a fight or flight
response. The fight or flight response is a
cascade of reactions that prepare the body to deal with sudden danger, reactions
such as increased heart rate to pump more oxygen containing blood to your muscles
and increased respiration rate to get more oxygen into your bloodstream, pupil
dilation to let more light into your eyes, and several other reactions.
In this diagram, we see an organ
known as your pancreas. This organ is tucked between your
stomach and your liver. The pancreas is the largest of the
endocrine glands. It also plays an important role in
producing enzymes for your digestive system, but its primary endocrine function is
to produce a hormone called insulin. Insulin’s main role is to regulate
blood glucose concentration. This is especially important
because, as you may recall, glucose is one of the reactants necessary for cellular
respiration. And cellular respiration is a
process that produces all of the energy that fuel our cells, which carry out all of
our essential life functions.
The last glands that we need to
take a look at are the gonads. In males, these are called
testes. And the female gonads are called
ovaries. The gonads produce hormones that
play a role in the endocrine system, but they are also obviously essential to the
reproductive system. The main hormones that they each
produce are estrogen from the ovaries and testosterone from the testes. These hormones play an important
role in development during puberty. And estrogen also influences the
menstrual cycle in females.
Now that we’ve learned some of the
basics of hormonal control, let’s take a closer look at a specific example.
Insulin is a hormone produced by
your pancreas. And you may recall its main job is
to regulate blood glucose concentration. Now, imagine that you’re enjoying a
sweet, delicious slice of birthday cake. All of those tasty simple
carbohydrates enter your bloodstream, and your blood glucose concentration begins to
rise. Your pancreas detects the rise in
blood glucose levels. It responds by producing insulin,
which also enters your bloodstream. The insulin circulates in the
bloodstream until it reaches its target cells. Here, we have a fat cell
pictured. The insulin binds to the receptors
on the target cells and causes them to take in the excess glucose. This reduces the glucose
concentration in your bloodstream, and the unnecessary insulin is eventually
removed.
If you enjoyed too many sugary
snacks, two things can happen. Your cells may become resistant to
insulin, meaning that the insulin in your blood stream will no longer cause the
cells to take in the excess glucose or the cells of your pancreas may become
damaged, causing them to produce less insulin. Either case can lead to a metabolic
disease called type two diabetes. So, be sure to enjoy those sugary
snacks sparingly.
Earlier, we started this video with
a brief discussion of how the endocrine system and the nervous system work together
to carry out the bodily function of control and integration of our other organ
systems. Before we move on to our practice
questions, we’ll take a moment to look at some of the similarities and differences
in the mechanisms of control that the endocrine system and the nervous system
utilize.
Well, we know that both the
endocrine system and the nervous system are responsible for sending messages
throughout your body and they’re both responsible for controlling and regulating
other bodily functions. As we’ve learned in this video,
your endocrine system achieves this through the use of glands, which secrete
hormones, which are chemical messengers that are transported through your
bloodstream. The bloodstream carries your
hormones throughout your entire body until they reach the target cells upon which
they act. For these reasons, the actions of
your endocrine system are both slower and longer lasting than those of your nervous
system.
In contrast, your nervous system
controls and regulates your body through the actions of neurons or nerve cells. Your nerve cells communicate using
impulses, which are electrical and chemical signals. These impulses travel to a specific
target, which means that the signal is more localized. For these reasons, the actions of
your nervous system tend to be faster but more short-lived than those of the
endocrine system.
Now that we’ve learned about the
endocrine system, glands, hormones, and their mechanisms of control, we’re ready to
try some practice questions.
Which of the following best defines
a hormone? (A) A hormone is a chemical
messenger transported by the blood stream. (B) A hormone is an electrical
messenger transported by the nervous system. (C) A hormone is a chemical
messenger transported by the nervous system. Or (D) a hormone is an electrical
messenger transported by the blood stream.
This question is asking us to read
through the answer choices and choose the response that best describes a
hormone. Hormones are a part of your
endocrine system. So, we’ll review some key facts
about the actions and mechanisms of your endocrine system in order to answer this
question.
Your endocrine system is an organ
system that consists of endocrine glands, an example of which is your pancreas. Endocrine glands are glands that
secrete hormones. In this case, your pancreas
secretes insulin. Hormones are chemical messengers
that are transported throughout the body in the bloodstream. The hormones circulate until they
reach their target cells upon which they act. With this information in mind,
we’re ready to choose our answer. A hormone is a chemical messenger
transported by the blood stream.
Let’s try a second practice
question.
The diagram shows a basic outline
of the major endocrine glands in the body. What endocrine gland is represented
by label A? What endocrine gland is represented
by label B? What endocrine gland is represented
by label C? And what endocrine gland is
represented by label D?
This question provides us with a
diagram of our major endocrine glands and then asks us to identify them based on
appearance and location. To answer this question, we’ll
simply identify what’s been labeled in this image, and then we’ll go ahead and
respond to each of the prompts.
I’ve added some hints to the
diagram that may help you recall the name of each of these glands. First, we have the gland known as
the master gland because it tends to act on the other glands of the endocrine
system. This gland is located deep within
the base of your brain. It’s called your pituitary
gland.
Our next gland produces a hormone
called thyroxine. Thyroxine is a hormone that helps
to control our metabolism. It also sounds a little bit like
the name of this gland, which is your thyroid.
Next, we have a pair of glands
known for making adrenaline. The name of these glands means
“near the kidneys,” which is appropriate since they sit right on top of them. These are your adrenal glands.
Finally, we have the largest gland
in your endocrine system. It’s known for producing the
hormone insulin. And insulin regulates your blood
glucose concentration. This very important gland is your
pancreas.
Now, let’s answer our
questions. The endocrine gland represented by
label A is the pituitary gland. The endocrine gland represented by
label B is the thyroid. The endocrine gland represented by
label C is an adrenal gland. And the endocrine gland represented
by label D is the pancreas.
Finally, let’s take a moment to
review what we’ve learned. In this lesson, we’ve learned that
glands secrete hormones. Hormones are transported by the
blood stream to the target cells, tissues, or organs upon which they act. We also reviewed the major glands
of the endocrine system and the hormones that they produce.
The pituitary gland, also known as
the master gland, is known for producing growth hormone. The thyroid produces a hormone
called thyroxine. Your adrenal glands produce a
hormone known as adrenaline. Your pancreas, very importantly,
produces insulin. The gonads are reproductive organs
that also play a role in the endocrine system. In females, you find ovaries, which
produce estrogen. And in males, you find the testes,
which produce testosterone.
