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The neuroendocrine system

The neuroendocrine system is made up of special cells called neuroendocrine cells. They are spread throughout the body. Neuroendocrine cells are like nerve cells (neurons), but they also make hormones like cells of the endocrine system (endocrine cells). They receive messages (signals) from the nervous system and respond by making and releasing hormones. These hormones control many body functions.

Where neuroendocrine cells are located

Neuroendocrine cells are found in almost every organ of the body. They are mainly found scattered in the gastrointestinal (GI) tract (including the small intestine, rectum, stomach, colon, esophagus and appendix), the gallbladder, the pancreas (islet cells) and the thyroid (C cells). Neuroendocrine cells are also commonly found in the lungs or airways into the lungs (bronchi), as well as the respiratory tract of the head and neck. The neuroendocrine cells scattered throughout these organs are often referred to as the diffuse neuroendocrine system.

The pituitary gland, the parathyroid glands and the inner layer of the adrenal gland (adrenal medulla) are almost all made up of neuroendocrine cells.

Other sites of neuroendocrine cells include the thymus, kidneys, liver, prostate, skin, cervix, ovaries and testicles.

Diagram of part of the neuroendocrine system

What neuroendocrine cells do

Neuroendocrine cells make and release hormones and similar substances (peptides) in response to neurological or chemical signals. The hormones then enter the blood and travel throughout the body to other cells (target cells). The hormones attach to specific receptors on target cells, which cause changes in the cells and what they do.

Neuroendocrine cells have many functions, which include controlling:

  • the release of digestive enzymes to break down food
  • how fast food moves through the GI tract
  • air and blood flow through the lungs
  • blood pressure and heart rate
  • the amount of sugar (glucose) in the blood
  • bone and muscle growth and development

The following are examples of hormones or peptides released by neuroendocrine cells and what they do.

  • Serotonin (5-HT or 5-hydroxytryptamine) is a chemical released by nerve cells (neurotransmitter) that helps with digestion. A lot of the body’s serotonin is found and made in the neuroendocrine cells of the GI tract where it controls the movement of food through the GI tract.
  • Gastrin tells the stomach to release acid and enzymes to help with digestion.
  • Insulin is made by pancreatic islet cells. It lowers the level of sugar (glucose) in the blood when it’s high. It controls when cells absorb (take up) sugar for energy.
  • Epinephrine (adrenaline) is made by neuroendocrine cells of the adrenal gland. It is released during times of stress, like when you feel fear, and increases heart rate and blood pressure.
  • Growth hormone is made in the pituitary gland. It promotes the growth and development of bones and muscles.

neuron

A specialized cell that sends and receives messages (electrical or chemical signals) within the nervous system.

Also called nerve cell.

endocrine system

The group of glands and cells in the body that make and release hormones (which control many functions such as growth, reproduction, sleep, hunger and metabolism) into the blood.

The endocrine system is made up of the hypothalamus, pituitary gland, pineal gland, thyroid, parathyroid gland, adrenal gland, pancreatic islet cells (also known as islets of Langerhans) and the ovaries or testicles.

nervous system

The network of neurons (nerve cells) throughout the body that work together to control organ functions and body movements.

The nervous system is made up of the central nervous system (CNS) and peripheral nervous system (PNS).

islet cell

A specialized cell in the pancreas that produces insulin and other hormones that help control the level of sugar (glucose) in the blood.

Also called endocrine pancreas cell or islet of Langerhans cell.

neurological

Having to do with nerves or the nervous system.

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