Pineal Gland

By Regina Bailey

Pineal Gland

The pineal gland is a small, pinecone shaped gland of the endocrine system. A structure of the diencephalon of the brain, the pineal gland produces the hormone melatonin. Melatonin influences sexual development and sleep-wake cycles. The pineal gland is composed of cells called pinealocytes and cells of the nervous system called glial cells. The pineal gland connects the endocrine system with the nervous system in that it converts nerve signals from the sympathetic system of the peripheral nervous system into hormone signals. Over time, calcium deposits build-up in the pineal and its accumulation often leads to calcification in the elderly.

Function

The pineal gland is involved in several functions of the body including:

• Secretion of the Hormone Melatonin
• Regulation of Endocrine Functions
• Conversion of Nervous System Signals to Endocrine Signals
• Causes Feeling of Sleepiness
• Influences Sexual Development

Location

Directionally the pineal gland is situated between the cerebral hemispheres and attached to the third ventricle.

It is located in the center of the brain.

Pineal Gland and Melatonin

Melatonin is produced within the pineal gland and synthesized from the neurotransmitter serotonin. Melatonin production is vital to the regulation of sleep-wake cycles and its production is determined by light and dark detection. The retina sends signals about light and dark detection to an area of the brain called the hypothalamus. These signals are eventually relayed to the pineal gland. The more light detected, the less melatonin produced and released into the blood. Melatonin levels are at their highest during the night and this promotes changes in the body that help us to sleep. Low levels of melatonin during daylight hours help us to stay awake.

Melatonin also influences the development of reproductive system structures. It inhibits the release of certain reproductive hormones from the pituitary gland that affect male and female reproductive organs. These pituitary hormones, known as gonadotropins, stimulate gonads to release sex hormones. Melatonin therefore regulates sexual development. In animals, melatonin plays a role in regulating mating seasons.

Images

• Histology: Pineal Gland
• Pineal Gland Sagittal View

More Information:

For additional information on the pineal gland, see:

• The Pineal Gland and Melatonin

Divisions of the Brain:

• Anatomy of the Brain
• Forebrain - consists of the Diencephalon and Telencephalon
• Midbrain
• Hindbrain - consists of the Metencephalon and Myelencephalon

_Sources:

• _{"pineal gland". Encyclopædia Britannica. Encyclopædia Britannica Online. Encyclopædia Britannica Inc., 2016. Web. 26 Jan. 2016 http://www.britannica.com/science/pineal-gland}
• _{"melatonin". Encyclopædia Britannica. Encyclopædia Britannica Online. Encyclopædia Britannica Inc., 2016. Web. 26 Jan. 2016 http://www.britannica.com/science/melatonin}