The pons is part of the brainstem, and in humans and other bipeds lies inferior to the midbrain, superior to the medulla oblongata and anterior to the cerebellum.
The brainstem is the posterior part of the brain, continuous with the spinal cord. In the human brain the brainstem includes the midbrain, and the pons and medulla oblongata of the hindbrain. Sometimes the diencephalon, the caudal part of the forebrain, is included.
The midbrain or mesencephalon is a portion of the central nervous system associated with vision, hearing, motor control, sleep/wake, arousal (alertness), and temperature regulation.
The medial lemniscus, also known as Reil's band or Reil's ribbon, is a large ascending bundle of heavily myelinated axons that decussate in the brainstem, specifically in the medulla oblongata. The medial lemniscus is formed by the crossings of the internal arcuate fibers. The internal arcuate fibers are composed of axons of nucleus gracilis and nucleus cuneatus. The axons of the nucleus gracilis and nucleus cuneatus in the medial lemniscus have cell bodies that lie contralaterally.
The lateral lemniscus is a tract of axons in the brainstem that carries information about sound from the cochlear nucleus to various brainstem nuclei and ultimately the contralateral inferior colliculus of the midbrain. Three distinct, primarily inhibitory, cellular groups are located interspersed within these fibers, and are thus named the nuclei of the lateral lemniscus.
The pontine nuclei are the nuclei of the pons involved in motor activity. The pontine nuclei are located in the ventral pons. Corticopontine fibres carry information from the primary motor cortex to the ipsilateral pontine nucleus in the ventral pons, and the pontocerebellar projection then carries that information to the contralateral cerebellum via the middle cerebellar peduncle. Extension of these nuclei in the medulla oblongata are named arcuate nucleus (medulla) which has the same function.
The dentate nucleus is a cluster of neurons, or nerve cells, in the central nervous system that has a dentate – tooth-like or serrated – edge. It is located within the deep white matter of each cerebellar hemisphere, and it is the largest single structure linking the cerebellum to the rest of the brain. It is the largest and most lateral, or farthest from the midline, of the four pairs of deep cerebellar nuclei, the others being the fastigial nucleus and the globose and emboliform nuclei which together are referred to as the interposed nucleus. The dentate nucleus is responsible for the planning, initiation and control of voluntary movements. The dorsal region of the dentate nucleus contains output channels involved in motor function, which is the movement of skeletal muscle, while the ventral region contains output channels involved in nonmotor function, such as conscious thought and visuospatial function.
A cranial nerve nucleus is a collection of neurons in the brain stem that is associated with one or more cranial nerves. Axons carrying information to and from the cranial nerves form a synapse first at these nuclei. Lesions occurring at these nuclei can lead to effects resembling those seen by the severing of nerve(s) they are associated with. All the nuclei except that of the trochlear nerve supply nerves of the same side of the body.
The septal nuclei are a set of structures that lie below the rostrum of the corpus callosum, anterior to the lamina terminalis. The septal nuclei are composed of medium-size neurons which are classified into medial, lateral, and posterior groups. The septal nuclei receive reciprocal connections from the olfactory bulb, hippocampus, amygdala, hypothalamus, midbrain, habenula, cingulate gyrus, and thalamus.
The tegmentum is a general area within the brainstem. The tegmentum is the ventral part of the midbrain and the tectum is the dorsal part of the midbrain. It is located between the ventricular system and distinctive basal or ventral structures at each level. It forms the floor of the midbrain (mesencephalon) whereas the tectum forms the ceiling.
It is a multisynaptic network of neurons that is involved in many subconscious homeostatic and reflexive pathways. It is a motor center that relays inhibitory signals to the thalamus and basal nuclei preventing unwanted body movement. The tegmentum area includes various different structures, such as the "rostral (=frontal/cranial/oral) end of the reticular formation, several nuclei controlling eye movements, the periaqueductal gray matter, the red nucleus, the substantia nigra, and the ventral tegmental area".
The cochlear nuclear (CN) complex comprises two cranial nerve nuclei in the human brainstem, the ventral cochlear nucleus (VCN) and the dorsal cochlear nucleus (DCN).
The ventral cochlear nucleus is unlayered whereas the dorsal cochlear nucleus is layered. Auditory nerve fibers, fibers that travel through the auditory nerve carry information from the inner ear, the cochlea, on the same side of the head, to the nerve root in the ventral cochlear nucleus.
At the nerve root the fibers branch to innervate the ventral cochlear nucleus and the deep layer of the dorsal cochlear nucleus. All acoustic information thus enters the brain through the cochlear nuclei, where the processing of acoustic information begins. The outputs from the cochlear nuclei are received in higher regions of the auditory brainstem.
The dorsal nucleus of the vagus nerve is a cranial nerve nucleus for the vagus nerve in the medulla that lies ventral to the floor of the fourth ventricle. It mostly serves parasympathetic vagal functions in the gastrointestinal tract, lungs, and other thoracic and abdominal vagal innervations. The cell bodies for the preganglionic parasympathetic vagal neurons that innervate the heart reside in the nucleus ambiguus.
In the ventral cochlear nucleus (VCN), auditory nerve fibers enter the brain via the nerve root in the VCN. The ventral cochlear nucleus is divided into the anterior ventral (anteroventral) cochlear nucleus (AVCN) and the posterior ventral (posteroventral) cochlear nucleus (PVCN). In the VCN, auditory nerve fibers bifurcate, the ascending branch innervates the AVCN and the descending branch innervates the PVCN and then continue to the dorsal cochlear nucleus. The orderly innervation by auditory nerve fibers gives the AVCN a tonotopic organization along the dorsoventral axis. Fibers that carry information from the apex of the cochlea that are tuned to low frequencies contact neurons in the ventral part of the AVCN; those that carry information from the base of the cochlea that are tuned to high frequencies contact neurons in the dorsal part of the AVCN. Several populations of neurons populate the AVCN. Bushy cells receive input from auditory nerve fibers through particularly large endings called end bulbs of Held. They contact stellate cells through more conventional boutons.
Medullary laminae of thalamus are layers of myelinated fibres that appear on cross sections of the thalamus. They also are commonly referred to as laminae medullares thalami or medullary layers of thalamus. The specific layers are:
The ventral pallidum (VP) is a structure within the basal ganglia of the brain. It is an output nucleus whose fibres project to thalamic nuclei, such as the ventral anterior nucleus, the ventral lateral nucleus, and the medial dorsal nucleus.
The VP is a core component of the reward system which forms part of the limbic loop of the basal ganglia, a pathway involved in the regulation of motivational salience, behavior, and emotions. It is involved in addiction.
The fields of Forel are areas in a deep part of the brain known as the diencephalon. They are below the thalamus and consist of three defined, white matter areas of the subthalamus. These three regions are also named "H fields":
The midbrain reticular formation (MRF) also reticular formation of midbrain, mesencephalic reticular formation, tegmental reticular formation, formatio reticularis (tegmenti) mesencephali) is a structure in the midbrain consisting of the dorsal tegmental nucleus, ventral tegmental nucleus, and cuneiform nucleus. These are also known as the tegmental nuclei.
