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Endocrine System: Hormones, Glands & How They Control Your Body 3d animation — Transcript

by Demystifying Science · 2,645 words · 464 segments · language en · Watch on YouTube

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0:00Inside your body, right now, a silent
0:02communication system is at work.
0:05It does not use nerves or electrical
0:07signals.
0:08Instead, it sends chemical messages
0:10through your blood. Messages that
0:12control how fast you grow, how you
0:15handle stress, how your body uses
0:17energy, and even your mood.
0:19This is the endocrine system. The
0:22endocrine system is a network of glands
0:25that produce and release chemical
0:26messengers called hormones.
0:29A gland is simply an organ that makes
0:31and releases a substance the body needs.
0:35The glands of the endocrine system
0:36release their hormones directly into the
0:39bloodstream, and the blood carries them
0:41all over the body.
0:43Now, before we go further, there is an
0:46important point to understand. The body
0:48actually has two different kinds of
0:50glands, and it helps to know the
0:52difference between them.
0:54The first kind is the endocrine gland,
0:56the type we are studying today.
0:58Endocrine glands release their hormones
1:00directly into the blood. They have no
1:02tubes or pipes. The bloodstream itself
1:05carries their message to the rest of the
1:07body.
1:08The second kind is the exocrine gland.
1:11Exocrine glands are different. Instead
1:13of releasing their product into the
1:15blood, they release it through small
1:17tubes called ducts onto a surface or
1:19into a space in the body.
1:21For example, sweat glands are exocrine
1:23glands. They release sweat through ducts
1:26onto the surface of your skin.
1:29Salivary glands are another example.
1:31They release saliva through ducts into
1:33your mouth.
1:34So, the key difference is simple.
1:37Endocrine glands send hormones into the
1:39blood with no ducts, while exocrine
1:41glands send their products through ducts
1:43to a surface.
1:45In this video, we are focused on the
1:47endocrine glands.
1:49Before we explore each gland in detail,
1:52let us take a quick tour and meet all
1:54the glands we we be discussing, moving
1:56from the top of the body downward. At
1:58the base of the brain is the pituitary
2:00gland, a tiny structure about the size
2:03of a pea.
2:04Just above it sits the hypothalamus, a
2:07small region of the brain itself.
2:10Deeper within the brain is the pineal
2:12gland, a tiny cone-shaped gland.
2:15Moving down into the neck, we find the
2:17thyroid gland, a butterfly-shaped gland
2:20wrapped around the front of the
2:22windpipe. Directly behind it are four
2:24very small parathyroid glands, each
2:27about the size of a grain of rice.
2:29Then, in the upper chest behind the
2:31breastbone, we have thymus gland. It has
2:33two main parts called lobes.
2:36Lower down, resting on top of each
2:38kidney, is an adrenal gland shaped like
2:40a small triangle or cap.
2:43Near the center of the abdomen, behind
2:45the stomach, lies the pancreas, a long,
2:48flat gland.
2:50And finally, in the lower body are the
2:52reproductive glands, the two oval-shaped
2:54testes in males, and the two
2:57almond-shaped ovaries in females. Those
3:00are the main players.
3:01Now that we have met them, let us
3:03understand the messengers they release,
3:06the hormones.
3:07You might be wondering what hormones are
3:09actually made of.
3:11Hormones are chemicals, but they are not
3:13all built from the same material.
3:15Most hormones fall into two main groups
3:18based on what they are made of.
3:20The first group is made from proteins or
3:22from the smaller building blocks of
3:23proteins called amino acids.
3:26Insulin and growth hormone are examples
3:28of this type.
3:30The second group is made from a type of
3:31fat or lipid called cholesterol.
3:35These are known as steroid hormones, and
3:37examples include cortisol, testosterone,
3:40and estrogen.
3:42A few hormones, such as adrenaline, are
3:44made from just a single amino acid.
3:47But whatever they are made of, all
3:49hormones do the same basic job. They
3:51carry a chemical message from a gland to
3:54the cells it needs to control.
3:56And that brings us to something
3:58interesting.
3:59Hormones travel everywhere through the
4:01blood, reaching almost every cell.
4:05But each hormone only affects certain
4:06cells, the ones it is meant to control.
4:09These are called its target cells.
4:12The reason is simple. A target cell has
4:14special structures called receptors,
4:16which fit that hormone like a key fits a
4:18lock.
4:20If a cell has the right receptor, the
4:22hormone can act on it. If it does not,
4:24the hormone simply passes by with no
4:27effect. This is how a single hormone,
4:29floating through the entire body, can
4:32deliver a precise instruction to exactly
4:34the right place.
4:36You might also wonder how this is
4:38different from the nervous system, which
4:40also sends messages around the body.
4:43The difference is speed and duration.
4:45The nervous system is fast, it sends
4:47electrical signals in a fraction of a
4:49second, and its effects are brief.
4:52Like pulling your hand away from
4:53something hot.
4:55The endocrine system is slower because
4:57its messages travel through the blood,
5:00but its effects last much longer, from
5:02minutes to hours, days, or even years.
5:06Think of the nervous system as sending a
5:08text message, and the endocrine system
5:10as sending a package through the mail.
5:13One is instant and quick, the other
5:15takes longer, but delivers something
5:17lasting.
5:18Together, these two systems keep your
5:20body balanced and coordinated. And that
5:23idea of balance is the key to everything
5:25the endocrine system does.
5:27Your body works best when its internal
5:29conditions, temperature, water levels,
5:32blood sugar, and more, stay within a
5:34narrow, healthy range. This state of
5:37internal balance is called homeostasis.
5:40The main job of the endocrine system is
5:42to maintain homeostasis, adjusting the
5:45body's chemistry to keep everything
5:47running smoothly.
5:48Now, let us travel back to the top of
5:50the body and explore each gland one by
5:53one.
5:54Our journey begins in the brain with the
5:56command center of the entire system.
5:59Deep in the brain sits a small region
6:01called the hypothalamus.
6:03The hypothalamus is the crucial link
6:05between the nervous system and the
6:07endocrine system.
6:08It constantly monitors the body's
6:10internal conditions and when something
6:12needs adjusting, it sends instructions
6:15to the gland just below it, the
6:17pituitary gland. The pituitary gland is
6:20about the size of a pea and it hangs
6:22from the base of the brain just beneath
6:24the hypothalamus.
6:26Despite its tiny size, it is often
6:28called the master gland because it
6:30controls many other glands in the body.
6:33When the hypothalamus gives it orders,
6:35the pituitary releases hormones that
6:37travel to other glands and tell them
6:39what to do.
6:40It also produces hormones of its own.
6:43So, let us go through the main ones. The
6:45first is growth hormone.
6:47As the name suggests, it controls the
6:48growth of your bones and muscles and it
6:51is especially active during childhood
6:53and the teenage years.
6:55Too little growth hormone in childhood
6:56can lead to unusually short height,
6:59while too much can cause excessive
7:01growth.
7:02The next few pituitary hormones are like
7:04managers. Their job is to control other
7:07glands.
7:08Thyroid stimulating hormone travels to
7:10the thyroid gland and tells it to
7:12release its hormones.
7:14Adrenocorticotropic hormone travels to
7:17the adrenal glands and tells them to
7:19release the stress hormone cortisol.
7:21And two hormones called follicle
7:23stimulating hormone and luteinizing
7:25hormone travel to the reproductive
7:27glands, controlling the production of
7:29sperm and eggs and the release of sex
7:32hormones.
7:33This is exactly why the pituitary earns
7:36the title of master gland. It gives
7:38orders to glands all over the body.
7:41The pituitary also produces prolactin,
7:44which stimulates the production of milk
7:46in mothers after childbirth.
7:49And it releases two more hormones,
7:51antidiuretic hormone, which tells the
7:53kidneys to conserve water and prevent
7:55the body from losing too much fluid,
7:58and oxytocin, which plays a key role
8:01during childbirth and in forming
8:02emotional bonds.
8:04Working alongside the pituitary is a
8:06tiny gland deeper in the brain called
8:09the pineal gland.
8:11It produces just one main hormone,
8:13melatonin, which controls your sleep and
8:16wake cycle.
8:18As night falls and light fades, the
8:20pineal gland releases more melatonin,
8:23making you feel sleepy.
8:26In the morning light, melatonin drops,
8:28helping you wake up. This is your body's
8:31natural internal clock at work.
8:34Now we move down into the neck, where we
8:36find one of the most important glands in
8:38the body, the thyroid gland.
8:41The thyroid is a butterfly-shaped gland
8:43that sits in the front of your neck,
8:44just below the voice box, wrapped around
8:46the windpipe.
8:48It produces two closely related hormones
8:50known as the thyroid hormones,
8:52thyroxine, often called T4, and
8:55triiodothyronine,
8:57often called T3.
8:59Together, these control your metabolism,
9:02the rate at which your body converts
9:04food into energy.
9:05Think of them as the body's accelerator.
9:08When the thyroid releases more of these
9:10hormones, your metabolism speeds up,
9:12your heart beats faster, you burn energy
9:15quicker, and you feel warmer.
9:17When it releases less, everything slows
9:19down.
9:21If the thyroid produces too little, a
9:23person may feel tired, cold, and gain
9:25weight.
9:26If it produces too much, they may feel
9:28restless, overheated, and lose weight.
9:31The thyroid produces one more hormone
9:34called calcitonin, which lowers the
9:36level of calcium in the blood when it
9:38rises too high.
9:40Sitting behind the thyroid are four tiny
9:42glands called the parathyroid glands.
9:46They produce a single hormone,
9:47parathyroid hormone,
9:49and its job is to control blood calcium,
9:52working opposite to calcitonin. Calcium
9:55is essential. Your muscles need it to
9:57contract, your nerves need it to send
9:59signals, and your bones need it for
10:01strength.
10:03When blood calcium drops too low, the
10:05parathyroid glands release their
10:07hormone, which pulls calcium from the
10:09bones back into the blood to restore the
10:11balance.
10:12So, the thyroid's calcitonin lowers
10:14calcium, and the parathyroid hormone
10:17raises it. Together, they keep calcium
10:19at exactly the right level.
10:22Moving down into the upper chest behind
10:24the breastbone, we reach a gland that is
10:26often forgotten, but very important,
10:28especially in childhood, the thymus.
10:32The thymus is a soft, two-lobed gland,
10:35and it produces hormones called
10:36thymosins.
10:38Their job is connected to the immune
10:39system, the body's defense against
10:41disease. The thymus is where a type of
10:44white blood cell called the T cell
10:46matures and learns to fight infections.
10:49The thymosins guide this training
10:51process.
10:52What makes the thymus unusual is its
10:54timing. It is largest and most active
10:56during childhood, when the immune system
10:58is being built, and it slowly shrinks
11:01after puberty as its main work is
11:02completed. This is why the thymus plays
11:05its biggest role in the early years of
11:07life.
11:08Continuing down the body, we arrive at
11:11two glands that sit on top of the
11:13kidneys, the adrenal glands.
11:16There is one adrenal gland above each
11:18kidney, and each has two parts that do
11:20different jobs.
11:22The inner part produces adrenaline, the
11:25hormone behind your body's response to
11:27fear, excitement, and danger.
11:30When you are suddenly frightened or
11:31under threat, your adrenal glands flood
11:34your blood with adrenaline. Your heart
11:37pounds, your breathing quickens, your
11:39pupils widen, and energy is released
11:42into your muscles.
11:44This is the famous fight-or-flight
11:46response, and it prepares your body to
11:48react instantly to an emergency.
11:51It is why you feel a rush before a big
11:53test, a race, or a scary moment. The
11:57outer part of the adrenal gland produces
11:59a different hormone called cortisol.
12:02Cortisol helps the body deal with
12:03longer-term stress and controls how the
12:06body uses energy from food. It also
12:09helps reduce inflammation.
12:11Cortisol is useful in the right amounts,
12:14but too much of it over a long time,
12:16from constant stress, can harm the body.
12:20Now we come to a truly special organ,
12:23the pancreas. The pancreas is unusual
12:26because it does two completely different
12:28jobs. Part of it helps digest food, but
12:31the part we care about here acts as an
12:33endocrine gland, controlling the level
12:35of sugar, or glucose, in your blood.
12:38Glucose is your body's main fuel, and
12:41keeping it balanced is critical.
12:44The pancreas does this using two
12:45opposing hormones.
12:47The first is insulin. When you eat a
12:50meal, the sugar in your blood rises.
12:53In response, the pancreas releases
12:55insulin, which signals your cells to
12:57absorb that sugar from the blood and use
12:59it for energy or store it for later.
13:02This brings blood sugar back down to a
13:04safe level.
13:05The second hormone is glucagon, which
13:08does the opposite. When blood sugar
13:10drops too low, for example, when you
13:12have not eaten for a while, the pancreas
13:14releases glucagon, which tells the liver
13:17to release stored sugar back into the
13:19blood, raising it again.
13:21Together, insulin and glucagon work like
13:24a seesaw, constantly balancing each
13:26other to keep blood sugar steady.
13:29When this system fails, when the body
13:31cannot produce enough insulin or stops
13:33responding to it, blood sugar rises to
13:36dangerous levels.
13:37This condition is called diabetes, one
13:40of the most common endocrine disorders
13:42in the world.
13:43Finally, our journey ends at the
13:45reproductive glands, also called the
13:47gonads.
13:49In males, these are the testes, and in
13:51females, they are the ovaries.
13:54These glands produce the hormones
13:56responsible for sexual development and
13:58reproduction.
13:59The testes produce testosterone, the
14:01main male hormone.
14:03During puberty, testosterone drives the
14:05development of male features, such as a
14:07deeper voice, facial hair, and increased
14:10muscle growth.
14:11The ovaries produce estrogen and
14:13progesterone, the main female hormones.
14:16These control the development of female
14:18features during puberty and regulate the
14:20monthly reproductive cycle.
14:23In both males and females, these
14:25hormones guide the enormous physical
14:27changes that transform a child's body
14:30into an adult's.
14:32So far, we have met the glands one by
14:34one.
14:36But the real power of the endocrine
14:37system comes from how they work
14:39together, and how the body knows exactly
14:42when to release a hormone and when to
14:43stop.
14:45The answer is a beautifully simple
14:47mechanism called feedback.
14:49Most hormones in the body are controlled
14:52by something called negative feedback.
14:54It sounds complicated, but the idea is
14:57easy.
14:58Negative feedback works like the
15:00thermostat in a house.
15:02You set a target temperature.
15:04When the room gets too cold, the heater
15:06switches on. Once the room reaches the
15:08right temperature, the heater switches
15:10off. The system corrects itself and then
15:12stops, keeping things balanced. Your
15:15hormones work the same way.
15:17Let us take the thyroid as an example.
15:20When the level of thyroid hormone in
15:21your blood gets too low, the
15:23hypothalamus and pituitary detect it and
15:26signal the thyroid to produce more.
15:28As the level rises back to normal, that
15:31same rising level signals the pituitary
15:33to stop sending the message.
15:35Production slows down. The system has
15:38corrected itself.
15:40This constant cycle of sensing and
15:42adjusting is what keeps hormone levels
15:45and the whole body in balance.
15:47We can see this teamwork clearly in a
15:50real situation.
15:52Imagine you have just eaten a large
15:54meal. Your blood sugar rises. The
15:56pancreas senses this and releases
15:58insulin, which moves the sugar into your
16:01cells and your blood sugar returns to
16:04normal.
16:05A few hours later, that sugar has been
16:07used up and your blood sugar starts to
16:10fall. Now the pancreas releases
16:12glucagon, which raises it back up again.
16:15You are not even aware of it, but
16:17throughout the day your endocrine system
16:19is constantly making these tiny
16:21adjustments to keep you alive and
16:22functioning.
16:24This is the true nature of the endocrine
16:26system.
16:27It is not a set of separate glands
16:29working alone.
16:30It is a connected network, coordinated
16:33by the brain, communicating through the
16:35blood, and constantly balancing itself
16:37through feedback.
16:39It manages your growth from infancy to
16:41adulthood, your energy every hour of the
16:44day, your response to danger, your
16:47sleep, and your reproduction.
16:49And it does all of this silently without
16:52you ever having to think about it. The
16:54next time you feel a rush of nerves
16:56before a big moment, feel sleepy at
16:58night, or feel your energy return after
17:00a meal, remember that is your endocrine
17:03system at work, keeping your body in
17:05perfect balance.

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