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The pineal gland (also known as the pineal body [1] or epiphysis cerebri) is a small endocrine gland in the brain of most vertebrates. It produces melatonin , a serotonin -derived hormone , which modulates sleep patterns following the diurnal cycles . [ 2 ]
Pinealocytes are the main cells contained in the pineal gland, located behind the third ventricle and between the two hemispheres of the brain.The primary function of the pinealocytes is the secretion of the hormone melatonin, important in the regulation of circadian rhythms. [1]
Melatonin, an indoleamine, is a natural compound produced by various organisms, including bacteria and eukaryotes. [1] Its discovery in 1958 by Aaron B. Lerner and colleagues stemmed from the isolation of a substance from the pineal gland of cows that could induce skin lightening in common frogs.
The endocrine glands belong to the body's control system. The hormones which they produce help to regulate the functions of cells and tissues throughout the body. Endocrine organs are activated to release their hormones by humoral, neural, or hormonal stimuli. Negative feedback is important in regulating hormone levels in the blood.
One of the most important functions of the hypothalamus—it is located in the brain adjacent to the pituitary gland—is to link the endocrine system to the nervous system via the pituitary gland.) Other organs, such as the kidneys , also have roles within the endocrine system by secreting certain hormones.
The pituitary gland (or hypophysis) is an endocrine gland about the size of a pea and weighing 0.5 grams (0.018 oz) in humans. It is a protrusion off the bottom of the hypothalamus at the base of the brain, and rests in a small, bony cavity (sella turcica) covered by a dural fold (diaphragma sellae).
The epithalamus is associated with sleep disorders like insomnia revolving around circadian rhythms of sleep wake cycles. The close connection of the epithalamus with the limbic system regulates the secretion of melatonin by the pineal gland and the regulation of motor pathways and emotions. [9] The secretion of melatonin happens in a cycle.
The pituitary gland is divided into three lobes: the anterior pituitary, the intermediate pituitary lobe, and the posterior pituitary. The hypothalamus controls the anterior pituitary's hormone secretion by sending releasing factors, called tropic hormones, down the hypothalamo-hypophysial portal system. [3]