The nervous system isn't the only regulatory system in the human body, the endocrine system is vital in maintaining homeostasis.
If you were to think of the nervous system as a telephone line, the endocrine system is like a radio broadcast. Nerve impulses travel in direct routes from A to B, and effect a small number of cells compared to endocrine messages. When the endocrine system releases hormones it is like a radio broadcast that is being sent to every cell, but only cells that are "tuned in" receive the message. These "tuned in" cells are called target cells, and receptors either on or in the cells are what "tunes" them in.
Hormones are "chemical messengers" that travel throughout the body via the blood stream. There are two types of hormones; steroid hormones and non-steroid or protein hormones. These hormones interact with our cells differently based on their ability to pass through the cell membrane or not.
A- The pituitary gland is often called the “master gland”. This pea-sized gland is responsible for releasing many hormones that regulate all other endocrine glands. Growth hormone for example is responsible for body development and conditions like gigantism or dwarfism can arise if it doesn’t function properly. Follicle-stimulating hormone (FSH) is also released here and is responsible for gamete production.
B- The hypothalamus is the link between the central nervous system and endocrine system. It is the part of the brain that is responsible for controlling the secretions of the pituitary.
C- The pineal gland releases melatonin, this hormone assists in the regulation of our circadian rhythm.
D- The thyroid gland secretes a number of iodine-based hormones including thyroxine, which is responsible for the metabolic rate of all body cells.
E- Located within the thyroid gland are four tiny parathyroid glands, they release parathyroid hormone which control calcium levels within the body
F- The thymus gland is most active during childhood and is responsible for the development of the immune system; late in life it atrophies and is where T cells mature.
I- The pancreas is both a digestive organ and an endocrine gland. It has specialized cells that produce insulin and glucagon, both of which regulate blood glucose levels. Insulin is responsible for storing glucose and lowering blood sugar levels whereas glucagon releases stored glucose and raises blood sugar levels
J- The adrenal glands sit above the kidneys and are responsible for regulating kidney function, producing cortisol which regulates the metabolism of organic compounds and epinephrine which increase blood flow and breathing rate.
L- The testes produce hormones such as testosterone that regulates sperm production and induce the development of secondary male characteristics
M- The ovaries produce hormones such as estrogen and progesterone, these regulates ova production and the menstrual cycle and induce the development of secondary female characteristics