The endocrine system and hormones

It’s early in the morning and Philip is in his bed. The sun is shining into the room. Philip has been awake all night because he and Kim were out looking at stars. Now, Philip can’t fall asleep. He’s yawning and he is really tired.

But even so, he can’t fall asleep. Why is that? Your body knows when you should be awake and when you should be asleep. It has an internal rhythm – the circadian rhythm. This is like an internal clock in your body, and it works by itself.

It controls different processes, like your sleep. The circadian rhythm is affected by how much light reaches your eyes and skin. With bright light, substances are formed in the body to help you to stay awake. And when it’s dark, other substances are formed to make you tired. These various substances are hormones.

Hormones are important for the body to function properly. But what are hormones and how are they formed? Hormones are formed in the body, in organs called glands. When the hormones are formed, they are transported by the blood to various parts of the body. There are hormones that affect almost all the cells in the body, while some affect only a few.

Different hormones have different tasks. Therefore, hormones can be compared to keys that fit special locks. The hormones search for recipient cells – “the locks”. When the keys – the hormones – don’t fit, they will not attach to the locks, but continue flowing with the blood. But when the hormones find recipient cells that do fit, then the hormones bind to those cells.

They are called target cells. Some hormones penetrate their target cells. Now, the body reacts, and this happens in different ways, depending on what hormones and what target cells are bound together. One example is that when it’s dark.. ..more sleep hormones are formed, and transported via the blood to their target cells. The hormones and the target cells bind together.

And eventually you get tired. ... and fall asleep Hormones control much more than the circadian rhythm. There are hormones that control the body’s ability to digest the food you eat, and then to use the energy from it to build up the body with new cells. These hormones control the metabolism. Other hormones control how you grow.

Some control the ability to feel sexual desire, or feel love. So, in your body there are many glands that form hormones – these glands are endocrine organs. The endocrine organs have different shapes and sizes. One of them is as small as a pea and weighs less than one gram. It’s positioned on the underside of the brain and is called the pituitary gland.

The pituitary gland forms several hormones, including the hormones that make you grow – growth hormones. The pituitary gland also forms hormones that help other glands in your body to form their hormones. For example, the hormones which stimulate the ovaries and testicals – the gonads – to form sex hormones, eggs, and sperm. This begins when you enter puberty. You can say that the pituitary gland has control over other endocrine organs in your body.

The endocrine organs, the hormones, and the target cells together are called the endocrine system. But what about Philip? He’s really tired, but can’t sleep because it’s too light. What should he do? He could close the curtains, and make it completely dark in the room.

And now, an endocrine organ, the pineal gland increases the production of a hormone that makes Philip tired: melatonin. Melatonin is a sleep hormone which affects target cells in the brain that match it. Philip, how does it feel now? I think it works. He’s fallen asleep.