The dorsal portion includes the lateral dorsal nucleus, pulvinar, and the lateral posterior nucleus. The lateral thalamus subdivides into dorsal and ventral components.
The medial thalamus integrates an immense amount of sensory data. The medial thalamus contains the dorsomedial nucleus and has connections with hypothalamic nuclei and the prefrontal cortex. The anterior thalamus contains the anterior thalamic nuclei that receive communication from the mammillary nuclei via the mammillothalamic tract and play a role in the limbic system. The thalamus divides into several components composed of different thalamic nuclei and tracts. The thalamus serves as a relay point for all sensory input tracts. The thalamus is the most substantial portion of the diencephalon, composing its remainder as two large oval masses flanking the third ventricle. The medial geniculate bodies are located inferior to the pulvinar and play a role in the auditory pathway. The pulvinar extends laterally to the lateral geniculate bodies which play a role in vision.
The posterior thalamus protrudes and overlaps the superior colliculus of the midbrain, the medial portion of this is the pulvinar. The hypothalamus is located in the anterior inferior portion of the diencephalon and includes the infundibulum, mammillary bodies, hypophysis, and many hypothalamic nuclei. The subthalamic nucleus participates in the regulation of movement with the basal ganglia. The subthalamus also contains the subthalamic nucleus at the base of the cerebral peduncle. The loss of neurons of the nucleus of Meynert occurs in several pathologies that result in dementia. The acetylcholine-producing neurons of the nucleus of Meynert are located within the subthalamus. The substantia nigra and red nucleus extend upward from the midbrain into the inferior subthalamus. The subthalamus is the upward continuation of the tegmentum of the midbrain and forms the greater part of the inferior portion of the third ventricle. The epithalamus is located in the posterior diencephalon and is composed of the pineal gland, habenular commissure, and posterior commissure. Some sources state the subthalamus is one of the four components of the diencephalon while others refer to the pretectum in place of the subthalamus however, both terms refer to the inferior portion of the diencephalon that is continuous with the midbrain. The diencephalon is composed of four major portions: the epithalamus, subthalamus, hypothalamus, and thalamus. This structure encompasses the third ventricle, which connects the interventricular foramen of the lateral ventricles to the cerebral aqueduct. The diencephalon is the most superior portion of the brainstem and connects to the midbrain inferiorly. This section overviews the major structures located in each area of the brainstem, followed by a summary of the course of the major pathways through the brainstem. The brainstem contains many different nuclei and tracts. The following activity addresses the nuclei, tracts, and functions of the brainstem. Clinicians can localize lesions of the brainstem with a thorough knowledge of brainstem anatomy and functions. Ten of the twelve cranial nerves arise from their cranial nerve nuclei in the brainstem. These tracts travel both to the brain (afferent) and from the brain (efferent) such as the somatosensory pathways and the corticospinal tracts, respectively. Some of the white matter tract cell bodies are located within the brainstem as well. The white matter tracts of the brainstem include axons of nerves traversing their course to different structures the axons originate from cell bodies located elsewhere within the central nervous system (CNS). The grey matter within the brainstem consists of nerve cell bodies and form many important brainstem nuclei. The brainstem contains many critical collections of white and grey matter. It is responsible for many vital functions of life, such as breathing, consciousness, blood pressure, heart rate, and sleep.
It is composed of four sections in descending order: the diencephalon, midbrain, pons, and medulla oblongata. The brainstem is the structure that connects the cerebrum of the brain to the spinal cord and cerebellum.