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Endocrine System:   Glands and Hormones

Endocrine System: Glands and Hormones

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This lesson will define examine the function of a hormone and the glands within the endocrine system.

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Tutorial

What's Covered

The nervous system provides one major way for the body to communicate. The brain processes information that's taken from all the rest of the body and sends out responses through the nerves to be carried out. So this provides quick, consistent sorts of responses that can be stored for later use in things like memory.

It is important to realize that the nervous system is not the only way that the body communicates. This tutorial will cover the endocrine system, specifically focusing on:

  1. Hormones
  2. Pituitary Gland
  3. Pineal Gland
  4. Thyroid Gland

1. HORMONES

There's another system in the human body called the endocrine system. The endocrine system is a system which uses chemicals secreted by glands that travel throughout the body and cause certain kinds of reactions.

These chemical communicators are called hormones. Hormones are chemicals that secreted by glands that affect different kinds of bodily functions and behaviors.

They're carried throughout the body by the bloodstream and the lymph system. And they can trigger different kinds of events. Or they can be triggered by different kinds of events, so the environment might create some kind of arousal within the body.

Example When you're scared by something, you get a surge of adrenaline. That is a hormone response that the endocrine system created.

Or there could be regular sorts of growth and life events which regulate the hormones that are being used in the body to send messages to the rest of the cells and the different parts.

Example In adolescence, there's a lot of hormones that are being sent to encourage growth in the body, especially secondary sexual characteristic growth.

Those are all aspects of hormones and the communication involved with the endocrine system.

Term to Know

    • Hormone
    • A chemical secreted by a gland that affects internal and external activities.

2. PITUITARY GLAND

Some of the most important glands in the endocrine system are located in the head and the neck area. The pituitary gland is an endocrine gland located towards the front, in the middle of the brain. And this is what we would call the "master gland."

It's a gland that controls the other glands within the body. It sends out signals telling when they should and should not release hormones for various kinds of functions. In this way, the pituitary gland is kind of the brain of the endocrine system.

However, it's important to note that it's actually being regulated largely by the hypothalamus, which is the organ that's just above it. And this provides a kind of link between these two communication systems, the nervous system and the endocrine system. The hypothalamus helps to tell the pituitary gland when it should send out those controlling hormones.

The pituitary gland also has an important function in secreting growth hormones. And growth hormones regulate the body's development over time. So at certain periods of a person's life, more growth hormones are being sent out. Too much or too little of these growth hormones can lead to different kinds of conditions, like dwarfism or gigantism.

Terms to Know

    • Growth Hormone
    • A hormone secreted during childhood, from the pituitary gland, that affects the physical growth of a person; too little can result in dwarfism while too much can result in gigantism.
    • Pituitary Gland
    • The "master gland" of the endocrine system; secretes hormones that affect other glands.

3. PINEAL GLAND

The pineal gland is another endocrine gland that's located in the brain; this one located a little bit more towards the center and middle of the brain. The pineal gland helps to regulate the body's rhythms and cycles.

Did You Know

Originally, a lot of people thought that the pineal gland was useless and convinced it was something left over from a previous time in human development, like the appendix.

The pineal gland secretes a hormone called melatonin. The pineal gland is sensitive to the amount of light within our environment. It's photosensitive. And so it'll secrete melatonin in larger amounts when there's more light. So in the beginning of the day, for example, it starts to secrete more melatonin. It secretes the most at around noontime, when we have the most light and then it starts to go gradually downhill towards nighttime. 

This actually affects the amount of arousal that we feel and our mood and activity throughout the day; this is why we feel sluggish a lot of times on a cloudy day. Overall, the pineal gland is a connection to the nervous system and affects the brain and personality.


4. THYROID GLAND

The thyroid glands are located within the neck. They control the rate of metabolism within the body. In other words, it tells the body how quickly it should make and use different sorts of energy.

You may have heard of different disorders that have to do with the thyroid gland, things like hyperthyroidism, which is when the thyroid produces too many hormones. This can lead to feelings of fatigue, because they're tired from using so much energy, as well as increased sweating and appetite, difficulty concentrating, nervousness or restlessness. You can see how this creates more energy in the body than a person can really use.

And the opposite of that is hypothyroidism, which is when there are too few hormones being produced. This can lead to feelings of depression, fatigue, weakness, as well as weight gain.

Needless to say, the thyroid gland has a powerful affect on a person's personality and mood. If somebody has hyperthyroidism, they might be a very excitable or irritable kind of person.

Term to Know

    • Thyroid Gland
    • Gland located in the neck which is responsible for the regulation of metabolism.

Summary

Hormones are chemicals that are secreted by glands that affect different kinds of bodily functions and behaviors. The pituitary gland controls the other glands within the body with the assistance of the hypothalamus. The pineal gland secretes a hormone called melatonin. The pineal gland is sensitive to the amount of light within our environment (i.e., photosensitive). Lastly, the thyroid gland controls metabolism.

Good luck!

Source: This work is adapted from Sophia author Erick Taggart.

Terms to Know
  • Growth Hormone

    A hormone secreted during childhood, from the pituitary gland, that affects the physical growth of a person; too little can result in dwarfism while too much can result in gigantism.

  • Hormone

    A chemical secreted by  a gland that affects internal and external activities.

  • Pituitary Gland

    The "master gland" of the endocrine system; secretes hormones that affect other glands.

  • Thyroid Gland

    Gland located in the neck which is responsible for the regulation of metabolism.