Diencephalon Section of the Brain

Hormones, Homeostasis, and Hearing Happen Here

Diencephalon
Structures of the diencephalon include the hypothalamus, thalamus, epithalamus, and subthalamus. Credit: SEER Training Modules / U. S. National Institutes of Health, National Cancer Institute

The diencephalon and the telencephalon (cerebrum) comprise the two major divisions of your prosencephalon or forebrain. If you were to look at a brain, with the skull removed, you would not be able to see the diencephalon, it is mostly hidden from view. It is a small part of the brain nested under and between the two cerebral hemispheres, just above the start of the midbrain's brain stem.

Despite being small in size, the diencephalon plays a number of critical roles in healthy brain and bodily function within the central nervous system.

Function

The diencephalon relays sensory information between brain regions and controls many autonomic functions of the peripheral nervous system.

It connects structures of the endocrine system with the nervous system and works with the limbic system structures to generate and manage emotions and memories. 

Several structures of the diencephalon work together and with other body parts to affect the following bodily functions:

  • Directing sense impulses throughout the body
  • Autonomic function control
  • Endocrine function control
  • Motor function control
  • Homeostasis
  • Hearing, vision, smell, and taste
  • Touch perception

Structures of the Diencephalon

The main structures of the diencephalon include the hypothalamus, thalamus, epithalamus (along with the pineal gland), and subthalamus. Also located within the diencephalon is the third ventricle, one of the four brain ventricles or cavities filled with cerebrospinal fluid.

Each part has its own role to play.

Thalamus

The thalamus assists in sensory perception, regulation of motor functions, and control of sleep and wake cycles. The brain has two thalamus sections. The thalamus acts as a relay station for almost all sensory information (with the exception of smell). Before the sensory information reaches your brain's cortex, it stops at the thalamus first.

The sensory information travels to the area (or nuclei) that specialize in dealing with that sensory information and then that information passes to the cortex for further processing. The thalamus processes information it receives from the cortex as well. It passes that information on to other parts of the brain and plays a big role in sleep and consciousness. 

Hypothalamus

The hypothalamus is small, about the size of an almond, and serves as the control center for many autonomic functions through the release of hormones. This part of the brain is also responsible for maintaining homeostasis, which is your body's attempt to maintain normal balance, for example, body temperature and blood pressure.

The hypothalamus receives a steady stream of information about these types of factors. When the hypothalamus recognizes an unanticipated imbalance, it enacts a mechanism to rectify that disparity.

As the main area that regulates hormone secretion and the control of hormone release from the pituitary gland, the hypothalamus has widespread effects on the body and behavior. 

Epithalamus

Located in the rear or bottom area of the diencephalon that includes the pineal gland, the epithalamus aids in sense of smell and helps to regulate sleep and wake cycles.

The pineal gland is an endocrine gland that secretes the hormone melatonin, which is thought to play an important role in the regulation of circadian rhythms responsible for sleep and wake cycles.

Subthalamus

A portion of the subthalamus is made of tissues from the midbrain. This area is densely interconnected with the basal ganglia structures that are part of the cerebrum, which assists in motor control.

Other Divisions of the Brain

There are three divisions of the brain. The diencephalon along with the cerebral cortex and brain lobes make up the forebrain. The other two parts are the midbrain and hindbrain. The midbrain is where the brain stem starts and connects the forebrain to the hindbrain. The brain stem travels all the way through the hindbrain. The hindbrain regulates autonomic functions and coordinates most bodily movement.