Pineal, Hypothalamus and Pituitary Glands
The pineal gland is a pinecone-shaped gland found in a groove between the two lobes of the brain. It is only about the size of a grain of rice and is pinkish-grey in colour. The pineal gland produces a hormone called melatonin whose main function is the regulation of the wake-sleep cycle. The pineal gland receives cues about the amount of light in the environmental and these cues trigger the pineal gland to produce melatonin. This melatonin instructs the body to make adjustments in temperature, blood pressure, alertness and other biological processes to facilitate sleeping or waking. Melatonin secretion peaks at night and ebbs during the day.
The hypothalamus is a gland about the size of a grape found in the central brain. It is part of both the neural system and the endocrine system and has two functions. Its primary function is to maintain balance within the body system. It does this by receiving nerve messages from the brain, translating them into chemical messages and relaying those new chemical messages to the pituitary gland. The pituitary receives these messages and in turn sends other chemical messages to the endocrine organs. In this way, our bodies are able to respond to sensations we feel about our surroundings without over or under-responding. Like a thermostat, the hypothalamus uses a set-point to regulate the body’s systems including electrolyte and fluid balance, body temperature, blood pressure, and body weight. It receives inputs from the body, then initiates compensatory changes if anything differentiates from this set-point. The set-point can migrate, but remains remarkably fixed from day-to-day. For this reason it is considered the “control centre” of the endocrine system. The second function of the hypothalamus is to manufacture the hormones needed to send these messages.
The pituitary gland is about the size of a pea and is located in the center of the brain behind the nose and eyes. It is attached to the hypothalamus by a slender stalk through which it receives chemical messages. The pituitary is sometimes referred to as the “master gland” because it directs the main hormone-producing glands in the body. The pituitary controls hormone functions such as temperature, thyroid activity, growth during childhood, urine production, testosterone production in males and ovulation and estrogen production in females. It does this by using hormones to send chemical messages to the other glands.
Major disorders of the pineal, hypothalamus or pituitary gland are usually diagnosed and treated during childhood.