The endocrine system is a collection of glands that release hormones which have an influence on almost every cell, organ, and function of the body.
Hormones are chemicals that carry messages from one cell to another through the bloodstream. The endocrine system regulates our mood, growth and development, the function of tissues, as well as metabolism and sexual function.
The endocrine system is in charge of body processes such as breathing and cell growth, which are controlled by hormones that transfer information and instructions from one set of cells to another. Many different hormones circulate throughout the bloodstream, and each one has a specific role. The levels of hormones circulating can be influenced by factors such as stress, infection, and changes in the balance of fluid and minerals in blood. In summary, the endocrine system produce’s chemicals called hormones, which are secreted directly into theblood stream, where they are then carried to their target organ.

The major glands that make up the human endocrine system include the:

• Hypothalamus
• Pituitary gland
• Thyroid
• Parathyroid’s
• Thymus
• Adrenal glands
• Pineal body
• Reproductive glands
• Pancreas

A gland has more than one function. It produces and secretes chemicals but it also selects and removes materials from the blood, processes them, and then secretes the finished chemical product to be used in a specific area in the body.

There are two different types of glands. Exocrine glands have ducts that carry their secretory product to a surface. Such glands include the sweat, sebaceous, and mammary glands. Endocrine glands release hormones directly into the blood stream for transportation around the body. Some other organs in the body, but not part of the endocrine system, also release hormones, such as the brain and heart.

The workings of the endocrine system
Once a hormone is secreted, it travels from the endocrine gland through the bloodstream to target cells designed to receive the message. During the transit to the cells, the hormones have special proteins bound to them. These proteins act as carriers that control the amount of hormones that are available to interact with and affect the target cells. Once at the target cells, receptors  within the cells attach themselves to specific hormones so that only those hormones communicate with the cells. The hormone locks onto the cells receptors and chemical instructions are transmitted to inside the cell. Once the hormone level reaches the required amount, any further secretions are controlled by mechanisms to maintain it.

We are going to look at each one in turn:

The hypothalamus
The hypothalamus is a small cone shaped structure of specialized cells that is located in the lower central part of the brain just above the brain stem. It acts as the primary link between the endocrine and nervous systems through the pituitary gland.
The hypothalamus has to respond to many different signals and has the
following functions:

• Controls the autonomic functions
• Controls emotions
• Plays a significant role in homeostasis
• Controls motor functions
• Regulates food and water intake
  Regulates the sleep and wake cycle

The hypothalamus controls the pituitary gland, which is sometimes referred to as the master gland, and sends hormones down to the pituitary gland.