Lesson Video: Hormones and the Body | Nagwa Lesson Video: Hormones and the Body | Nagwa

Lesson Video: Hormones and the Body Science

In this video, we will learn how to describe the effects of different hormones produced by the pituitary gland and outline the specific functions of hormones produced by the thyroid gland, gonads, pancreas, and adrenal glands.

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Video Transcript

In this video, we are going to explore the effects of different hormones produced by the various endocrine glands of our body. We will outline the pituitary gland located under the brain which is often called the master gland because of the control it has on other endocrine glands. We will also see how other endocrine glands play many diverse roles in our bodies controlling our reproduction, growth, metabolism, responses to danger, and even our emotions. We will understand how all these glands play that part so that our body maintains a constant and healthy state despite all of the changes going on within us and around us.

Hormones are chemical messengers that are produced by the cells in endocrine glands and are secreted into the bloodstream. In the blood, these hormones can travel around the entire body. Eventually hormones will reach their target cells, upon which the hormones can cause a specific effect. In humans, the main endocrine glands include the pituitary gland, the thyroid gland, the pancreas, the adrenal glands, and the gonads. The gonads in biological females are the ovaries, while the gonads in biological males are the testes. However, on this diagram, we’ve shown both.

As we mentioned earlier once hormones reach their target cells, they can induce different responses. For example, they can regulate cellular functions to aim to adapt our body to changes occurring in our internal and the external environment. An example of an internal change in the environment might be eating sugar, or a change in our external environment could be when facing a sudden danger. The responses to these changes aim to maintain the normal functioning of the body. As a result, we usually say that hormones contribute to homeostasis, which is our body’s capacity to maintain constant conditions despite all the changes going on within us and around us.

Now, let’s take a tour of the major endocrine glands in the body, starting with the pituitary gland. This gland is quite small, about the size of a pea. It’s divided into two lobes and is located just under the brain. Even though the pituitary gland is one of the smallest glands in our body, it is sometimes called the master gland because some pituitary hormones can control many other endocrine glands, for example, the thyroid gland.

Let’s look at an example of a hormone produced by the pituitary gland that has an effect on the thyroid gland. This hormone is called thyroid-stimulating hormone or TSH. And it’s secreted into the blood vessels that surround the pituitary gland. As is suggested by its name, thyroid-stimulating hormone can then travel via the bloodstream to the thyroid gland. When TSH reaches the thyroid gland, which is located in the front base of the neck, it instructs specific thyroid cells to produce and secrete another hormone called thyroxine. Thyroxine can then travel via the bloodstream to have an effect on various target cells. For example, thyroxine can modulate our energy level, our metabolism, our growth, and even our brain, heart, muscle, and digestive system function.

Another hormone that’s produced by the thyroid gland is called calcitonin. This hormone is not controlled by the pituitary gland but by the level of calcium in the blood, as indicated by its name calcitonin. Calcium is the most abundant mineral in our body. As you might know, it’s very important to build our bones but also for our muscles to contract and for our nervous system to function properly. Calcitonin helps to maintain an adequate level of calcium in our bloodstream. The pituitary gland also releases hormones that have a direct effect on many types of cells in the body. One example is growth hormone or GH.

GH acts primarily on our bone and on our muscle cells, determining their development and growth. This is the hormone that helps determine how tall you are. Without enough growth hormone, dwarfism may occur, causing the height of some people to remain under 120 centimeters. By contrast to GH which has so many effects on various cell types in the body, some hormones released by the pituitary gland can have an effect on just one specific organ of our body. That’s the case with antidiuretic hormone often known as ADH, which acts primarily on the kidneys to prevent them from eliminating too much water. For example, if you’re stuck in a hot desert without much to drink, your body needs to be very savvy with the water that it contains. The action of ADH can be vital in these situations to retain more water within the bloodstream.

The other lobe of the pituitary gland secretes a hormone that should not be confused with ADH. This hormone is called adrenocorticotropic hormone or ACTH for short. ACTH changes the activity of the endocrine glands that are located just on top of each kidney which are called the adrenal glands. Under the activation of ACTH, the adrenal glands release another hormone. This hormone is called cortisol, and it’s very important to mediate our response to stress. Sometimes, stress can be very sudden, for example, when we are surprised by a storm with lightning and thunder. In this case, our body needs to react fast to this acute stress or immediate danger.

In these cases, the adrenal glands secrete another hormone called adrenaline. This hormone makes us react faster than cortisol and triggers what we call a fight-or-flight response. In this type of response, adrenaline activates many of our body functions such as increasing the blood flow to our muscles, increasing heart rate, and dilating the bronchioles in the lungs among others that help us to escape or fight through a dangerous situation. A pituitary hormone that’s worth mentioning is oxytocin. Oxytocin is involved in childbirth by inducing contractions of the uterus. Oxytocin also plays a role in milk ejection. Prolactin, another pituitary hormone, stimulates milk production in a biological female’s mammary glands, usually around the midpoint of pregnancy. Oxytocin induces this milk ejection from the mammary glands.

Oxytocin also has important effects on the brain. It’s an important influencer of social bonding and emotional responses, such as trust, empathy, and positive communication. That’s why it’s sometimes called the love hormone. The pituitary gland also secretes hormones called gonadotropins. As indicated by their name, gonadotropins control the activity of the gonads. The gonads are our sexual glands that produce the gametes for our reproduction and a series of sex hormones. In biological females, the gonads are the ovaries, while in biological males, the gonads are the testes. Let’s see how these hormones work.

The reaction starts at a time called puberty. This is a period of maturation during which our body acquires its adult features. During this time, our body goes through lots of changes developing various secondary sexual characteristics. For example, under the effect of testosterone, which is released from the males testes, biological males tend to develop more muscle mass and experience increased growth of facial and body hair. Under the effect of estrogen that’s produced in the ovaries of biological females, however, breasts tend to develop, in addition to the widening of the hips and various other physical characteristics.

Puberty in biological females is also when the menstrual cycle begins, which means that during this cycle an egg is released from the ovaries during ovulation. In parallel, the lining of the uterus builds up to prepare for a possible pregnancy. Progesterone is a hormone that’s secreted from the ovaries to thicken the lining of the uterus which is also called the endometrium. If there is no pregnancy, this lining shades away during menstruation which is sometimes called a period, and then a new menstrual cycle can start. Thanks to the pituitary gland, we’ve been able to review most of the main endocrine glands of the body already. But you might have noticed there’s one last endocrine gland that we should mention that plays a vital role in our body that’s called the pancreas.

The pancreas is unique because parts of it act as an exocrine gland, secreting enzymes to support digestion, whereas other endocrine cells secrete hormones into the blood. The hormones that are secreted by the pancreas are involved in controlling the level of glucose in the blood. When we eat food, it travels through our digestive system where some of it is broken down into glucose. This glucose then dissolves in the bloodstream. Glucose can then be delivered via the blood to all the body cells that need it. This allows the cells to release energy through cellular respiration. To be able to take up glucose from the blood, most cells of our body, like our muscle cells, need to receive a hormone that’s produced by the pancreas. This hormone is called insulin.

The glucose that is not used by the cells is stored in the liver in the form of glycogen. This provides an energy source that can be used at a later date when no food is available, for example, during periods of fasting. When no food is available to the body, the level of glucose in the blood decreases. This triggers other cells in the pancreas to release a different hormone called glucagon, which directs the liver to break down glycogen into glucose. Glucose can be then released into the blood to return blood glucose to a normal level. In this manner, the hormones insulin and glucagon can keep glucose within a normal range. Now that we know more about the main endocrine glands of the body, let’s see how much we’ve learned by applying our knowledge to some practice questions.

Which of the following are two hormones secreted by the pituitary gland? (A) Growth hormone and thyroid-stimulating hormone, (B) calcitonin and insulin, (C) growth hormone and insulin, or (D) thyroid-stimulating hormone and thyroxine.

Hormones are chemical messengers that are produced in endocrine glands and secreted into the bloodstream. Once in the blood, they can travel around the body to cause an effect on specific target cells. These effects include responses that regulate bodily functions to adapt to changes in the internal and external environment to maintain the normal functioning of the body. Let’s take a look at some specific endocrine glands within the human body to work out which of the hormones are secreted by the pituitary gland.

The pancreas is an endocrine gland that secretes a hormone called insulin. Insulin is involved in regulating blood glucose levels. As we know that this hormone is not secreted by the pituitary gland but by the pancreas, we can eliminate options (B) and (C). The thyroid gland is a butterfly-shaped endocrine gland located at the front base of the neck. The thyroid gland secretes a hormone called thyroxine, which is involved in energy metabolism. It also secretes a hormone called calcitonin, which is involved in regulating the level of calcium in our blood. As we know that thyroid gland and not the pituitary gland secretes thyroxine, we can also eliminate option (D).

The pituitary gland is a pea-sized endocrine gland located just under the brain. It secretes a number of different hormones, some of which can control other endocrine glands. For this reason, the pituitary gland is sometimes called the master gland. One such hormone is thyroid-stimulating hormone, sometimes called TSH, which stimulates the thyroid gland to release the thyroid hormones. The pituitary gland also releases a hormone called growth hormone that plays a role in the growth of tissues. Therefore, we’ve worked out that growth hormone and thyroid-stimulating hormone are two hormones that the pituitary gland can secrete.

Let’s try another practice question together.

The figure shows changes in the endometrium of the uterus during a 28-day menstrual cycle. Which hormone stimulates the thickening of the uterine lining, endometrium, from day 19 to 28? (A) Testosterone, (B) progesterone, (C) glucagon, (D) thyroid hormone, or (E) growth hormone.

The pituitary gland is an endocrine gland that’s located just under the brain. It’s sometimes called the master gland as it can secrete hormones that have effects on other endocrine glands. In biological females, one of these endocrine glands that the pituitary gland hormones can target are the ovaries. The pituitary gland secretes hormones called gonadotropins. In biological females, gonadotropins regulate the production of the hormones estrogen and progesterone in the ovaries. Estrogen is involved in the development of secondary sex characteristics when a person reaches puberty.

In females, this might include the development of breasts and starting the menstrual cycle. Estrogen also plays a part in regulating the menstrual cycle, which is shown in the diagram as provided to us by the question. During the menstrual cycle, an egg cell is released from one of the ovaries in a process called ovulation. During this time, the uterine lining, which is otherwise known as the endometrium, thickens to be prepared if an egg cell is fertilized by a sperm cell. This is because a resulting embryo if this fertilization occurs will implant into the endometrium. Progesterone is the hormone that’s responsible for thickening this endometrium layer from day 19 to approximately day 28 of the menstrual cycle.

If pregnancy occurs, progesterone levels remain high, so the endometrium layer remains thick to support the development of the baby. However, if fertilization, and therefore pregnancy, does not occur, then the endometrium is shed through a process called menstruation or sometimes a period. This begins the menstrual cycle again, and then the uterine lining will thicken once more as the levels of progesterone start to increase again. Therefore, we’ve worked out that the hormone that stimulates the thickening of the uterine lining or the endometrium during the menstrual cycle is progesterone.

Let’s try one more question together.

The figure shows some of the body’s responses to fear and stress, which are coordinated by one main hormone X. What is hormone X? (A) Glucagon, (B) insulin, (C) adrenaline, (D) testosterone, or (E) thyroxine.

Hormones are chemical messengers that travel throughout the body via the bloodstream to cause an effect. They have diverse functions, and each hormone has a specific target. Some hormones can be involved in reproduction, growth, homoeostasis, and some in response to fear and stress caused by dangerous situations. Hormones are secreted by endocrine glands, an example of which are the adrenal glands. Humans typically have two adrenal glands, one of which sits above each of our kidneys. Depending on the situation, the adrenal glands can produce two main responses to cope with stress. One of these responses involves the release of the hormone cortisol. Cortisol is used in more long-term responses, modulating our metabolism and immune response.

The other response involves the hormone adrenaline. It’s a short-term response produced to react to acute stress or immediate danger. Adrenaline induces the fight-or-flight response, which has many functions in the body. It can increase the blood flow to muscles, increase the heart rate, and can even dilate the bronchioles, which are the air passages leading to the lungs, allowing more oxygen to enter the bloodstream. This is how our body prepares to fight through or escape from a dangerous situation. Therefore, we’ve worked out that hormone X is adrenaline.

Let’s summarize what we’ve learned in this video. Hormones are chemical messengers that travel in the blood to coordinate different responses. The pituitary gland produces many hormones and can control the action of other endocrine glands. Some examples of hormones produced by the pituitary gland are growth hormone, prolactin, oxytocin, and thyroid-stimulating hormone. Thyroid-stimulating hormone stimulates the thyroid gland to release thyroxine. To control the level of calcium in the blood, the thyroid gland also releases the hormone calcitonin.

The pancreas secretes two main hormones that are involved in glucose homoeostasis, insulin and glucagon. The adrenal glands produce many hormones, one of which is involved in the fight-or-flight response to stressful situations, adrenaline. The gonads include the testes in biological males and the ovaries in biological females. While the testes mainly secrete testosterone, the ovaries mainly secrete estrogen and progesterone.

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