Hormones: Definition, Function & Intro to the Endocrine System

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  • 0:43 What are Hormones?
  • 1:23 Endocrine Glands
  • 3:48 Location of Endocrine Glands
  • 6:28 Lesson Summary
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Lesson Transcript
Instructor: Kimberly Carpenter

Kimberly has an undergraduate degree in Lab Sciences and a Master's degree in Education.

This lesson introduces the endocrine system and provides a brief overview of each endocrine gland. It also provides the definition of hormones and describes their general function inside the body.


What are hormones? You have most likely heard of hormones at some point in your lifetime and may think you know what they do. Well, the truth of the matter is that hormones and their function within the endocrine system are extremely complex. There are multiple glands throughout the body, and each gland produces specific hormones designed to carry out certain functions. The whole process is actually quite amazing! It also has the potential to be very overwhelming at times. Never fear, because you are about to learn a general overview of this highly important system.

What Are Hormones?

Hormones are actually tiny chemical messengers located inside of your body. They are unable to be seen with the human eye and travel throughout the internal superhighway - otherwise known as the bloodstream - to all of your body's organs and tissues. Different hormones perform specific roles inside of your body. Some of these hormones work quickly to start or stop a process, and some will continually work over the course of a long period of time to perform their necessary jobs. Some of these jobs include the body's growth and development, metabolism (or production of energy), sexual function and reproduction.

The Endocrine Glands

The endocrine glands are a highly specialized group of cells responsible for making hormones. These glands are located throughout your entire body. Each gland plays a specific role in the production of a particular hormone or group of hormones needed to carry out the necessary duties required by your body to help the body remain in a state of homeostasis, or continual balance. The body requires a continual state of balance in order to function at its maximum level of efficiency. If, for any reason, your body is ever found to be outside of homeostatic balance, there could be significant negative results if the body is not repaired within a certain period of time.

For example, if a person is exposed to cold weather for an extended period of time, the body's internal temperature begins to fall. The body's temperature must remain within a certain range in order for the continual balance of homeostasis to occur and ensure all organs and systems are functioning properly. In order to remain in homeostatic balance, certain hormones are sent to specific cells and tissues to trigger a sensation which generates heat within the body and causes you to experience things such as shivering and the chattering of your teeth. These indications remind you that it is time to find a warmer location so your body may begin working to restore its internal temperature back to the range needed for proper body functions to occur. If the body temperature continues to fall, and you are unable to find a way to generate the heat required to reverse this problem, organs and systems will slowly begin to fail.

Hormones bind to receptor sites on the targeted tissues or cells.
Binding Sites

The endocrine glands and their related organs operate like small factories. They produce and store the gland-specific hormones until the time comes for those hormones to be released to a particular site in the body. The specific endocrine gland will receive a message from the pituitary gland, which is also known as the master gland, stating how much hormone is needed and where this hormone is to travel. The hormone then begins its journey through the superhighway of the bloodstream and continues along this path until it reaches the targeted tissues or cells. These tissues and cells will contain receptors located along their outside walls to serve as binding sites for the attachment of the hormone. Once the hormone has attached to one of the binding sites, the hormone is now in a position to carry out its specific role in helping maintain your body's homeostatic balance.

Location of the Endocrine Glands

When we visualize the human body, starting with the head, we can locate the pituitary gland and pineal gland inside of the brain. The pituitary gland is normally found inside of the skull, just above the nasal passages. It is considered the master gland because of its responsibility to ensure the timely production and delivery of every hormone in the body. Its assistant, the hypothalamus, while not officially considered a major endocrine gland, serves an essential role in helping with the delivery of messages to and from each respective endocrine gland throughout the body. This relationship controls the amount of hormone secreted from various glands during a particular period of time. The hypothalamus is actually located quite close to the pituitary, sitting directly above the brain stem. The pineal gland is a small, pea-sized gland located towards the back portion of the brain and is responsible for your body's circadian rhythm, or internal clock.

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