Diencephalon Section of the Brain

The diencephalon and the telencephalon (or cerebrum) comprise the two major divisions of your prosencephalon. If you were to look at a brain, you would not be able to see the diencephalon in the forebrain because it is mostly hidden from view. It is a small portion nestled under and between the two cerebral hemispheres, located just above the brain stem.

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

Diencephalon Function

The diencephalon relays sensory information between brain regions and controls many autonomic functions of the peripheral nervous system. This section of the forebrain also connects structures of the endocrine system with the nervous system and works with the limbic system to generate and manage emotions and memories. 

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

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

Structures of the Diencephalon

The main structures of the diencephalon include the hypothalamus, thalamus, epithalamus, 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 of the diencephalon has its own role to play.

Thalamus

The thalamus assists in sensory perception, motor function regulation, and sleep cycle control. The thalamus acts as a relay station for almost all sensory information (with the exception of smell). Before sensory information reaches your brain's cortex, it stops at the thalamus. The thalamus processes information and passes it along. Input information then travels to the correct area of specialty and is passed to the cortex for further processing. The thalamus also 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 the balance of your body's systems including body temperature and blood pressure.

The hypothalamus receives a steady stream of information about bodily functions. When the hypothalamus detects an unanticipated imbalance, it employs a mechanism to counteract the disparity. As the main area that regulates hormone secretion (including hormone release from the pituitary gland), the hypothalamus has widespread effects on the body and behavior. 

Epithalamus

Located in the bottom area of the diencephalon, the epithalamus aids with sense of smell and also helps to regulate sleep and wake cycles. The pineal gland found here 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 regular sleep and wake cycles.

Subthalamus

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