Location, and Function of the Diencephalon
The diencephalon is a part of the prosencephalon of the brain. It connects the nervous system with the endocrine system and is thus responsible for the regulation of many vital functions of the human body.
Located between the cerebrum and the upper part of the brain stem, the diencephalon receives sensory information from the stimuli received through the dedicated areas in the central nervous system.
After that, it translates them into chemical and electrical signals that are sent to the neuron cells of the pituitary gland which regulates and controls the activity of the endocrine system. In turn, this gland signals the excretion of hormones upon being activated.
By secreting neurohormones (a blend of neurotransmitters and hormones released by neurons), the diencephalon plays a very important role in the regulation of our sleep, alertness, and wakefulness. It also manages our emotions, memories, appetite, blood pressure, and sleep, and plays a part in childbirth.
Which Brain Structures Comprise the Diencephalon?
The diencephalon consists of 4 elements: the epithalamus, thalamus, subthalamus, metathalamus, and the hypothalamus. It also enfolds a cavity of the brain labeled as the third ventricle. The third ventricle of the diencephalon is filled with cerebrospinal fluid.
What Is the Structure and Function of the Thalamus?
Among all the brain structures comprising the diencephalon, the thalamus is the largest one. It’s located in the middle of the human brain and serves as the largest relay center of the information gained from the sensory organs.
Structure of the Thalamus
The thalamus comprises of the following nuclei:
- Anterior nuclei – Consisting of the anteroventral nucleus, anteromedial nucleus, and anterodorsal nucleus.
- Medial nuclei – Consisting of the dorsomedial nucleus and midline nucleus.
- Lateral nuclei – Consisting of the dorsal group (lateral dorsal, lateral posterior, and pulvinar nuclei), the ventral group (ventral anterior, ventral lateral, ventral posterior, ventral posterior medial, ventral posterior lateral, and ventral posterior inferior nuclei), and the metathalamic nuclei (medial geniculate nucleus, and lateral geniculate nucleus).
- Intralaminar nuclei – Consisting of the centromedian nucleus and parafascicular nucleus.
- Reticular nuclei – Consisting of the reticular thalamic nucleus.
Function of the Thalamus
The thalamus receives sensory and motor information from our bodies and the environment in order to transmit them to the other brain structures, such as the cerebral cortex, which processes the information and sends out the appropriate response.
This part of the brain has a significant role in the regulation of the voluntary motor movement. Namely, the coordination, cadence, planning, initiation, and coordination of movements are all being controlled by an interaction of the thalamus and the motor cortex.
Furthermore, the thalamus is significant for the vital processes of the human body. They include the regulation of the sensation of taste, the sensations of touch, temperature, pain, as well as the higher cognitive functions that are also processed in this brain center.
What Is the Structure and Function of the Subthalamus?
The subthalamus is in charge of the higher cognitive processes such as the formation of thoughts and sentences. It also regulates the skeletal muscle movement by receiving axon connections from the neuron cells comprising the substantia nigra and the striatum.
Located under the back part of the thalamus and behind the hypothalamus, this part of the diencephalon consists of the following nuclei:
- Zona incerta
- Reticular nucleus
- Perigeniculate nucleus
In addition, the dendrites of the cells comprising the aforementioned nuclei branch out and form connections with the cerebral cortex, putamen, globus pallidus, trigeminal nuclei, cerebellar nuclei, and pretectal region.
In correlation with these brain structures, the subthalamus regulates and controls cardiovascular activity, and also relays the sensory information on our water intake (the hydration of our body), our sexuality, food intake, etc.
What Is the Structure and Function of the Hypothalamus?
This brain structure is located near the limbic system. It functions as a primary brain area that receives sensory information from the stimuli.
The hypothalamus is an area of the brain located below the thalamus. It consists of a cluster of neurons that are arranged in nuclei. They can be divided into two zones: the medial and the lateral zone.
Medial Zone
The medial zone of the hypothalamus contains the following nuclei:
- A part of the preoptic nucleus
- A part of the suprachiasmatic nucleus
- Lateral nucleus
- Tuberomammillary nucleus
- Lateral tubular nuclei
Lateral Zone
The lateral zone of the hypothalamus contains the nuclei listed below:
- Part of the lateral nucleus
- Part of the suprachiasmatic nucleus
- Anterior nucleus
- Paraventricular nucleus
- Dorsomedial nucleus
- Ventromedial nucleus
- Infundibular nucleus
- Posterior nucleus
The hypothalamus is responsible for the control of the body’s autonomic nervous system, as well as the regulation of various vitally important biological processes. These include: body temperature, blood pressure, thirst, hunger, the sleep-wake cycle, important aspects of parenting and attachment behaviors, fatigue, etc.
For instance, when the hypothalamus receives information about the presence or absence of light, it sends a signal that activates the pineal gland, which starts or inhibits cortisol and melatonin production, both responsible for the regulation and control of the sleep/wake cycle.
What Is the Structure and Function of the Epithalamus?
The epithalamus is a small region of the diencephalon including the pineal gland, as well as a region in the roof of the third ventricle of the brain. It connects the limbic system to the other parts of the cerebral cortex of the brain.
This brain area is comprised of the following structures that are part of the sympathetic nervous system:
- Stria medullaris
- Posterior commissure
- Habenular nuclei (medial and lateral)
- Pineal body
- Paraventricular nuclei (anterior and posterior)
The epithalamus also has an active role in the secretion of melatonin, the manner in which energy is stored in our body.
In addition, the epithalamus is also responsible for the regulation of our motor pathways and emotions.
What Is the Structure and Function of the Third Ventricle of the Brain?
The third ventricle of the brain is a cavity filling the space between the two hemispheres of the diencephalon of the forebrain. The third ventricle performs several functions in the brain:
- It protects the brain from trauma. The third ventricle plays a vital role in the protection of the brain from injuries.
This structure of the human brain is filled with cerebrospinal fluid that largely cushions any inflicted physical trauma on the brain, thus protecting it.
Also, the third ventricle aids the circulation of the blood that nourishes the central nervous system.
- It aids the circulation of the cerebrospinal fluid which cushions the brain. The cerebrospinal fluid flows from the lateral ventricles, through the interventricular foramina, and then reaches the third ventricle and drains via this brain structure.
From here, it continues to flow into the fourth ventricle of the brain, via a brainstem structure labeled as the cerebral aqueduct. In this way, the third ventricle serves as a pathway of the cerebrospinal fluid of the brain.
- The third ventricle of the human brain also supports the transportation of the nutrients and waste from the central nervous system by aiding the flow of the cerebrospinal fluid.
Namely, after passing through the ventricular system of the brain, the cerebrospinal fluid of the brain again becomes absorbed in the bloodstream.
In this way, it rinses the metabolic waste from the central nervous system.
What Is the Cerebrospinal Fluid of the Brain And What Is Its Function?
The cerebrospinal fluid is a colorless liquid substance that cushions both the brain and the spinal cord within the bony structures of the skull. To be more specific, it is composed of low protein plasma and a small number of cells.
It protects the brain when the blood pressure fluctuates, but also nourishes and cleanses the central nervous system’s environment.
Additionally, the cerebrospinal fluid serves as the means of transmission of the signals relayed by the synapsing cells in the cerebral cortex.
What Happens if the Diencephalon Is Damaged or Dysfunctional?
The functions of the diencephalon can be interrupted by damage or injury to any of its structures. Disorders of the diencephalon (or any of its structures, respectively) can be caused by one or more triggering factors, which include:
- Head trauma (concussions)
- Brain trauma
- Aging
- Substance abuse
- Narrowing of the arteries that provide blood to the brain
- Vitamin deficiencies
- Brain tumor
- Inherited genetic diseases (such as Alzheimer’s disease)
- Mental health conditions (such as depression or anxiety)
Hence, a dysfunctional diencephalon can lead to an interruption in the transmission of sensory data between key memory structures, as well as to various medical conditions such as:
- Severe and long-lasting amnesia – A gradual forgetfulness which can lead to a complete loss of memory.
- Diencephalic syndrome – A brain disorder in infants and children, located in the diencephalon. This neurological disorder is caused by a tumor and includes symptoms such as hyperactivity or euphoric behavior, anemia, hypoglycemia, as well as extremely low blood pressure (as a less common symptom).
- Dysrhythmia – Incoordination of movement, as well as an abnormal rhythm and timing of the movements of the extremities.
To Sum Up
The diencephalon is a part of the forebrain that is in charge of a great number of vital functions of the human body. Supported by its comprising structures (epithalamus, thalamus, subthalamus, metathalamus, and the hypothalamus), it regulates and controls the sleep and wake cycles, childbirth, the regulation of appetite, emotions, the formation and storage of memories, the control of motor movements, the temperature of the body, etc.
The thalamus is the largest part of the diencephalon.
Furthermore, the diencephalon serves as a primary relay center for the processing of sensory information. The diencephalon also controls the autonomic functions of the human body.
Namely, it aids our memory and emotions by interacting and establishing connections with the limbic system and the primary sensory areas of the cerebral cortex of the brain.
Also, the diencephalon and the corresponding structures of the brain support the motor coordination by establishing connections with the basal ganglia.
Fun Facts
Did you know?
- The diencephalon is also known as a between brain or interbrain. The name of this brain structure derives from the Ancient Greek words διά (diá, meaning: through) and ἐγκέφαλος (enképhalos, meaning: brain).
- Circadian rhythm refers to the internal body clock that is responsible for the regulation of the 24-hour cycles of our biological processes. They include the sleep and wake cycles, hormone production, the regeneration of the cells, the feeding patterns, the body-temperature cycle.
Basically, the circadian rhythm cycle denotes the mental, behavioral, and physical changes that occur in a daily cycle.
The circadian rhythm also regulates some of the longer cycles of the body, such as the monthly menstrual cycle in women.
- The thalamus is the part of the brain which gives us consciousness. Namely, it helps us be awake, alert, and active, regulates our sleep, etc.
- Together with the hypothalamus, the thalamus regulates emotions and motivated behaviors like sexuality and hunger.
- Aging is typically associated with both impairments of the circadian system and a decrease in melatonin secretion.
- While the hypothalamus can be compared to an almond in size, the thalamus can be compared to a walnut.
- The hypothalamus plays the role of the body’s thermostat, as it’s responsible for the stimulation of the temperature of our blood, by either increasing it or by triggering the sweat glands in order to lower the body’s temperature..
- The neural projections and endocrine hormones are the two major types of output of the hypothalamus.
- Apart from its role in the control of the circadian cycle, the epithalamus plays a significant role in the regulation of emotion, too.
- The major component of the learning process is the control and flow of dopamine.