The arcuate nucleus is a cluster of nerve cells located in the hypothalamus, which connects to the pituitary gland and controls the body’s endocrine system. There are several types of neurons, or nerve cells, within the structure, including those that regulate hormones including dopamine. Some neurons control the production or secretion of growth hormone-releasing hormone (GHRH). Other nerve cell groups regulate appetite as well as sexual behavior. There is also an arcuate nucleus in the medulla oblongata of the brain, which controls sensitivity to chemical compounds as well as the rate of breathing.
Many nerve cells in the arcuate nucleus project deep into the hypothalamus. Some are involved in controlling appetite. These typically contain substances like neuropeptide Y and agouti-related protein. The nerve cells can trigger someone to eat substantial amounts of food when activated, and are usually regulated by appetite-stimulating hormones like ghrelin and leptin.
Other neurons in the arcuate nucleus have peptides based on pro-opiomelanocortin; cells with this compound can also regulate sexual behavior. These cells typically project into many parts of the brain. Some cells, called tuberoinfundibular dopamine neurons, in the arcuate nucleus also influence the release of dopamine into the blood. Nerve endings from here that end in the pituitary gland can help to regulate prolactin, which usually stimulates milk production in women who are nursing babies.
There are some neuroendocrine neurons in the arcuate nucleus that include GHRH and somatostatin neurons. Somatostatin generally inhibits the release of growth hormone, but these cells often help to switch between the production of one or the other substance. The alternated secretion and blocking of growth hormone is typically the result, maximizing its benefits to the body.
Neurons in the arcuate nucleus that control growth hormones as well as lactation are generally considered neuroendocrine neurons. They can trigger compounds to be released into the blood stream. Appetite stimulating cells are often referred to as centrally projecting because they have extensions into the hypothalamus as well as other parts of the brain.
Damage to this area can cause a complete loss of appetite, even when the body requires nutrition. When the arcuate nucleus functions normally, hormones such as laptin and ghrelin in the blood can trigger neurons that regulate the sensation of hunger. The structure is generally thought to be a junction point between neurological activity and the hormones that are released into and acquired from the blood supply.