Table of ContentsView AllTable of ContentsAnatomyFunctionAssociated ConditionsTests

Table of ContentsView All

View All

Table of Contents

Anatomy

Function

Associated Conditions

Tests

The diencephalon has a central location within the human brain sitting just above the brain stem. It is divided into four main structures—the thalamus,hypothalamus, epithalamus, and subthalamus.

The diencephalon is involved in many crucial bodily functions including coordinating with theendocrine systemto release hormones, relaying sensory and motor signals to the cerebral cortex, and regulating circadian rhythms (the sleep wake cycle).

Structures that make up the diencephalon are also involved in regulating body temperature, appetite, and more. Dysfunction of any of these crucial parts of the human brain can result in serious health conditions.

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Thalamus and hypothalamus in the diencephalon of the brain

In adults, the diencephalon is centrally located within the brain sitting at the top of the brain stem above the midbrain and under thecerebrum. It is part of the third ventricle of the brain. Along with the cerebrum, the diencephalon is part of the forebrain. Theoptic nerveconnects the eyes to several structures located within the diencephalon.

Thalamus

The thalamus looks like two paired “bulbs” consisting of mostly grey matter that sit on each side of the third ventricle of the brain. These bulbs sit atop the subthalamus and are also connected to the epithalamus. The two parts of the thalamus are connected via the interthalamic adhesion.

Multiple nerve fibers connect the thalamus to the cerebral cortex. It is supplied with blood via four arteries the tuberothalamic artery, the paramedian artery, the thalamogeniculate artery, and the medial and lateral posterior choroidal artery.

Epithalamus

The stria medullaris is also a group of nerve fibers that connects the septal nuclei, lateral preoptic hypothalamic region, and anterior thalamic nuclei to the habenula. The pineal gland is unpaired and approximately 5-7 millimeters (mm) in size.

Subthalamus

Ventral to the thalamus is the subthalamus. The main structure within the subthalamus is the subthalamic nucleus which is divided into three subsections, the dorsolateral motor territory, ventromedial associative territory, and medial limbic territory.

Other important structures within the subthalamus include the zona incerta, the reticular nucleus, and the perigeniculate nucleus.

Hypothalamus

The hypothalamus is a very small cone-shaped structure that lies beneath the thalamus. Despite its small size, it is one of the most important structures in the human brain. The hypothalamus ends in the pituitary stalk (also called the infundibular stalk) which connects it to thepituitary gland.

The median eminence is a collection of nerve endings from neurosecretory cells that run the length of the pituitary stalk to the pituitary gland. Other adjacent structures include the mammillary bodies and theoptic chiasm.

Each of the four structures located within the diencephalon plays a critical role in normal brain functioning which we will discuss individually.

The thalamus also receives sensory and motor signals from the body and relays this information to the cerebral cortex. It plays a crucial role in regulating consciousness and alertness.

The epithalamus contains the pineal gland which secretesmelatonin. Melatonin is responsible for the sleep-wake cycle (circadian rhythm) in humans. Nerve pathways also connect the epithalamus with the limbic system and basal ganglia.

Like other parts of the diencephalon the subthalamus is home to many groups of nerves that connect various parts of the brain. It also is a control center for theperipheral nervous systemand connects the endocrine system with the nervous system and limbic system. The subthalamus has different parts including:

The hypothalamus is known for maintaininghomeostasis. Homeostasis is a state of balance, wellness ,or proper functioning in a sense. It can be described as internal stability.

The hypothalamus communicates with the pituitary gland which is often called the master gland. Signals coming from the hypothalamus cause other endocrine glands in the body to release vital hormones. For example, it signals theadrenal glandsto release cortisone or thethyroid glandto release thyroid hormones.

Due to the wide range of physiological functions that take place in the diencephalon, dysfunction due to a genetic condition, disease (such as a lesion or tumor) or injury (lack of oxygen, stroke, or traumatic accident for example), occurring in any location of this part of the brain can be devastating.

Additionally any disruption to components of the diencephalon and the neurotransmitters or hormones these areas are involved in regulating may contribute to the development of psychiatric illnesses such asschizophreniaor clinical depression.

The following conditions involve a disorder of the thalamus:

Any injury or problem that impairs proper functioning of the epithalamus or especially the pineal gland can lead to psychiatric problems such as mood disorders, issues with the sleep-wake cycle, and more. The following conditions are associated with dysfunction of the epithalamus:

Some of the following conditions are related to injury or dysfunction of the subthalamus:

What Are Hypothalamus Disorders?

A wide variety of tests are available to test brain function including problems in the diencephalon. They may include but are not limited to:

10 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Medicine Libretexts.Functions of the diencephalon.Shahid Z, Asuka E, Singh G.Physiology, hypothalamus. StatPearls.Torrico TJ, Munakomi S.Neuroanatomy, thalamus. StatPearls.Medicine LibreTexts.Epithalamus and pineal gland.Brain Made Simple.Subthalamus.Bear MH, Reddy V, Bollu PC.Neuroanatomy, hypothalamus.StatPearls.MedlinePlus.Hypothalmic dysfunction.Ilahi S, Beriwal N, Ilahi TB.Physiology, pineal gland. StatPearls.Northwestern Medicine.Huntington’s disease linked to dysfunction of brain structure.University of Texas Medical Branch.Disorders of the hypothalamus and pituitary gland.

10 Sources

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Medicine Libretexts.Functions of the diencephalon.Shahid Z, Asuka E, Singh G.Physiology, hypothalamus. StatPearls.Torrico TJ, Munakomi S.Neuroanatomy, thalamus. StatPearls.Medicine LibreTexts.Epithalamus and pineal gland.Brain Made Simple.Subthalamus.Bear MH, Reddy V, Bollu PC.Neuroanatomy, hypothalamus.StatPearls.MedlinePlus.Hypothalmic dysfunction.Ilahi S, Beriwal N, Ilahi TB.Physiology, pineal gland. StatPearls.Northwestern Medicine.Huntington’s disease linked to dysfunction of brain structure.University of Texas Medical Branch.Disorders of the hypothalamus and pituitary gland.

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

Medicine Libretexts.Functions of the diencephalon.Shahid Z, Asuka E, Singh G.Physiology, hypothalamus. StatPearls.Torrico TJ, Munakomi S.Neuroanatomy, thalamus. StatPearls.Medicine LibreTexts.Epithalamus and pineal gland.Brain Made Simple.Subthalamus.Bear MH, Reddy V, Bollu PC.Neuroanatomy, hypothalamus.StatPearls.MedlinePlus.Hypothalmic dysfunction.Ilahi S, Beriwal N, Ilahi TB.Physiology, pineal gland. StatPearls.Northwestern Medicine.Huntington’s disease linked to dysfunction of brain structure.University of Texas Medical Branch.Disorders of the hypothalamus and pituitary gland.

Medicine Libretexts.Functions of the diencephalon.

Shahid Z, Asuka E, Singh G.Physiology, hypothalamus. StatPearls.

Torrico TJ, Munakomi S.Neuroanatomy, thalamus. StatPearls.

Medicine LibreTexts.Epithalamus and pineal gland.

Brain Made Simple.Subthalamus.

Bear MH, Reddy V, Bollu PC.Neuroanatomy, hypothalamus.StatPearls.

MedlinePlus.Hypothalmic dysfunction.

Ilahi S, Beriwal N, Ilahi TB.Physiology, pineal gland. StatPearls.

Northwestern Medicine.Huntington’s disease linked to dysfunction of brain structure.

University of Texas Medical Branch.Disorders of the hypothalamus and pituitary gland.

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