Pontine tegmentum | |
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![]() Brainstem -- tegmentum not labeled, but is visible near center | |
Details | |
Identifiers | |
Latin | tegmentum pontis |
MeSH | D065821 |
NeuroNames | 557 |
NeuroLex ID | birnlex_923 |
TA98 | A14.1.05.301 |
TA2 | 5929 |
FMA | 71108 |
Anatomical terms of neuroanatomy |
The pontine tegmentum, or dorsal pons, is the dorsal part of the pons located within the brainstem. The ventral part or ventral pons is known as the basilar part of the pons. The pontine tegmentum is all the material dorsal from the basilar pons to the fourth ventricle. Along with the dorsal surface of the medulla oblongata, it forms part of the rhomboid fossa – the floor of the fourth ventricle.
Its contents include several cranial nerve nuclei, the reticulotegmental nucleus, the pedunculopontine nucleus and the laterodorsal tegmental nucleus. It also houses the pontine respiratory group of the respiratory center which includes the pneumotaxic centre, and the apneustic centre.
The pontine tegmentum contains nuclei of the cranial nerves (trigeminal (5th), abducens (6th), facial (7th), and vestibulocochlear (8th) and their associated fibre tracts. The dorsal pons also contains the reticulotegmental nucleus, the mesopontine cholinergic system comprising the pedunculopontine nucleus and the laterodorsal tegmental nucleus. In the respiratory center of the dorsal pons are the pontine respiratory group and the parabrachial nuclei in the pneumotaxic centre, and the apneustic centre. Nearby important structures include the cranial nerve nuclei of the oculomotor (3rd) and trochlear (4th) nerve nuclei, which are located in the midbrain. The pontine nuclei are located within the basilar pons. Also nearby are the raphe nuclei and the locus coeruleus, nuclei of cranial nerves 9-12, and the dorsal respiratory group, which are located further caudally in the brainstem. The dorsal respiratory group are connected to the pneumotaxic and apneustic centres of the pontine tegmentum.
Thanks to the number of different nuclei located within the pontine tegmentum, it is a region associated with a range of functions including sensory and motor functions (due to the cranial nuclei and fiber tracts), control of stages of sleep and levels of arousal and vigilance (due to the ascending cholinergic systems), and some aspects of respiratory control. [1]
The pontine tegmentum contains nuclei of several cranial nerves and consequently has a role in several groups of sensory and motor processes.
The pontine tegmentum contains two predominately cholinergic nuclei, the pedunculopontine nucleus (PPN) and the laterodorsal tegmental nucleus, which project widely throughout the brain. [2]
The PPN is involved in many functions, including arousal, attention, learning, reward, and voluntary limb movements and locomotion. [3] [4] While once thought important to the initiation of movement, recent research suggests a role in providing sensory feedback to the cerebral cortex. [3] Recent research has discovered that the PPN is involved in the planning of movement, and that different networks of neurons in the PPN are switched on during real and imagined movement. [4]
It is also implicated in the generation and maintenance of REM sleep. [5] In animal studies, lesions of the pontine tegmentum greatly reduce or even eliminate REM sleep. Injection of a cholinergic agonist (e.g. carbachol), into the pontine tegmentum produces a state of REM sleep in cats. PET studies seem to indicate that there is a correlation between blood flow in the pontine tegmentum and REM sleep [6]
Pontine waves, (PGO waves) or P-waves in rodents, are brain waves generated in the pontine tegmentum. They can be observed in mammals to precede the onset of REM sleep, and continue throughout its course. After periods of memory training, P-wave density increases during subsequent sleep periods in rats. This may be an indication of a link between sleep and learning.
The two respiratory areas – the pneumotaxic center and the apneustic center make up the pontine respiratory group that provide antagonistic control signals to the dorsal respiratory group (DRG) located in the medulla. Increased input from the pneumotaxic center decreases the duration and increases the frequency of bursts of activity in the DRG, producing shorter and more frequent inhalations. The apneustic center delays the end of a burst in the DRG, extending periods of inhalation.
The medulla oblongata or simply medulla is a long stem-like structure which makes up the lower part of the brainstem. It is anterior and partially inferior to the cerebellum. It is a cone-shaped neuronal mass responsible for autonomic (involuntary) functions, ranging from vomiting to sneezing. The medulla contains the cardiac, respiratory, vomiting and vasomotor centers, and therefore deals with the autonomic functions of breathing, heart rate and blood pressure as well as the sleep–wake cycle. "Medulla" is from Latin, ‘pith or marrow’. And "oblongata" is from Latin, ‘lengthened or longish or elongated'.
The pons is part of the brainstem that in humans and other mammals, lies inferior to the midbrain, superior to the medulla oblongata and anterior to the cerebellum.
The brainstem is the stalk-like part of the brain that connects the forebrain with the spinal cord. In the human brain, the brainstem is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is continuous with the thalamus of the diencephalon through the tentorial notch.
In neuroanatomy, the trigeminal nerve (lit. triplet nerve), also known as the fifth cranial nerve, cranial nerve V, or simply CN V, is a cranial nerve responsible for sensation in the face and motor functions such as biting and chewing; it is the most complex of the cranial nerves. Its name (trigeminal, from Latin tri- 'three' and -geminus 'twin') derives from each of the two nerves (one on each side of the pons) having three major branches: the ophthalmic nerve (V1), the maxillary nerve (V2), and the mandibular nerve (V3). The ophthalmic and maxillary nerves are purely sensory, whereas the mandibular nerve supplies motor as well as sensory (or "cutaneous") functions. Adding to the complexity of this nerve is that autonomic nerve fibers as well as special sensory fibers (taste) are contained within it.
The midbrain or mesencephalon is the rostral-most portion of the brainstem connecting the diencephalon and cerebrum with the pons. It consists of the cerebral peduncles, tegmentum, and tectum.
The reticular formation is a set of interconnected nuclei that are located in the brainstem, hypothalamus, and other regions. It is not anatomically well defined, because it includes neurons located in different parts of the brain. The neurons of the reticular formation make up a complex set of networks in the core of the brainstem that extend from the upper part of the midbrain to the lower part of the medulla oblongata. The reticular formation includes ascending pathways to the cortex in the ascending reticular activating system (ARAS) and descending pathways to the spinal cord via the reticulospinal tracts.
The laterodorsal tegmental nucleus is a nucleus situated in the brainstem, spanning the midbrain tegmentum and the pontine tegmentum. Its location is one-third of the way from the pedunculopontine nucleus to the thalamus, inferior to the pineal gland.
The pedunculopontine nucleus (PPN) or pedunculopontine tegmental nucleus is a collection of neurons located in the upper pons in the brainstem. It is involved in voluntary movements, arousal, and provides sensory feedback to the cerebral cortex and one of the main components of the reticular activating system. It is a potential target for deep brain stimulation treatment for Parkinson's disease. It was first described in 1909 by Louis Jacobsohn-Lask, a German neuroanatomist.
A cranial nerve nucleus is a collection of neurons in the brain stem that is associated with one or more of the 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 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 facial motor nucleus is a collection of neurons in the brainstem that belong to the facial nerve. These lower motor neurons innervate the muscles of facial expression and the stapedius.
The vestibular nuclei (VN) are the cranial nuclei for the vestibular nerve located in the brainstem.
The sensory trigeminal nerve nuclei are the largest of the cranial nerve nuclei, and extend through the whole of the midbrain, pons and medulla, and into the high cervical spinal cord.
The lateral hypothalamus (LH), also called the lateral hypothalamic area (LHA), contains the primary orexinergic nucleus within the hypothalamus that widely projects throughout the nervous system; this system of neurons mediates an array of cognitive and physical processes, such as promoting feeding behavior and arousal, reducing pain perception, and regulating body temperature, digestive functions, and blood pressure, among many others. Clinically significant disorders that involve dysfunctions of the orexinergic projection system include narcolepsy, motility disorders or functional gastrointestinal disorders involving visceral hypersensitivity, and eating disorders.
Foville's syndrome is caused by the blockage of the perforating branches of the basilar artery in the region of the brainstem known as the pons. It is most frequently caused by lesions such as vascular disease and tumors involving the dorsal pons.
The respiratory center is located in the medulla oblongata and pons, in the brainstem. The respiratory center is made up of three major respiratory groups of neurons, two in the medulla and one in the pons. In the medulla they are the dorsal respiratory group, and the ventral respiratory group. In the pons, the pontine respiratory group includes two areas known as the pneumotaxic center and the apneustic center.
The salivatory nuclei are pre-ganglionic parasympathetic neurons in the caudal pons representing the general visceral efferent (GVE) cranial nerve nuclei giving rise to axons which join the facial nerve and glossopharyngeal nerve to reach and innervate the salivary as well as lacrimal glands. The nuclei may also be involved in parasympathetic control of head vasculature.
The parabrachial nuclei, also known as the parabrachial complex, are a group of nuclei in the dorsolateral pons that surrounds the superior cerebellar peduncle as it enters the brainstem from the cerebellum. They are named from the Latin term for the superior cerebellar peduncle, the brachium conjunctivum. In the human brain, the expansion of the superior cerebellar peduncle expands the parabrachial nuclei, which form a thin strip of grey matter over most of the peduncle. The parabrachial nuclei are typically divided along the lines suggested by Baxter and Olszewski in humans, into a medial parabrachial nucleus and lateral parabrachial nucleus. These have in turn been subdivided into a dozen subnuclei: the superior, dorsal, ventral, internal, external and extreme lateral subnuclei; the lateral crescent and subparabrachial nucleus along the ventrolateral margin of the lateral parabrachial complex; and the medial and external medial subnuclei
The parafacial zone (PZ) is a brain structure located in the brainstem within the medulla oblongata believed to be heavily responsible for non-rapid eye movement (non-REM) sleep regulation, specifically for inducing slow-wave sleep.