Pontine tegmentum

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Pontine tegmentum
Pons section at facial colliculus.png
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 located within the brainstem, and is one of two parts of the pons, the other being the ventral pons or basilar part of the pons. The pontine tegmentum can be defined in contrast to the basilar pons: basilar pons contains the corticospinal tract running craniocaudally and can be considered the rostral extension of the ventral medulla oblongata; however, basilar pons is distinguished from ventral medulla oblongata in that it contains additional transverse pontine fibres that continue laterally to become the middle cerebellar peduncle. The pontine tegmentum is all the material dorsal from the basilar pons to the fourth ventricle. Along with the dorsal surface of the medulla, it forms part of the rhomboid fossa – the floor of the fourth ventricle.

Contents

The pontine tegmentum contains nuclei of the cranial nerves (trigeminal (5th), abducens (6th), facial (7th), and vestibulocochlear (8th) cranial nerve nuclei) and their associated fibre tracts, the tegmental pontine reticular nucleus, the mesopontine cholinergic system comprising the pedunculopontine nucleus and the laterodorsal tegmental nucleus, and in the respiratory center the pontine respiratory group – 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, which are located within the basilar pons, and the raphe nucleus and the locus ceruleus, 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.

Function

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]

Functions of the cranial nerve nuclei

The pontine tegmentum contains nuclei of several cranial nerves and consequently has a role in several groups of sensory and motor processes.

Functions of the mesopontine cholinergic system

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.

Function of the respiratory group

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.

See also

Related Research Articles

Cranial nerves Nerves that emerge directly from the brain and the brainstem

Cranial nerves are the nerves that emerge directly from the brain, of which there are conventionally considered twelve pairs. Cranial nerves relay information between the brain and parts of the body, primarily to and from regions of the head and neck, including the special senses of vision, taste, smell, and hearing.

Medulla oblongata Structure of the brain stem

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.

Pons Part of the brainstem in humans and other bipeds

The pons is part of the brainstem that in humans and other bipeds lies inferior to the midbrain, superior to the medulla oblongata and anterior to the cerebellum.

Brainstem Posterior part of the brain, adjoining and structurally continuous

The brainstem is the posterior stalk-like part of the brain that connects the cerebrum 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, and sometimes the diencephalon is included in the brainstem.

Trigeminal nerve Cranial nerve V, for the face

The trigeminal 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" = tri-, or three, and - geminus, or twin: so "three-born, triplet") 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.

Midbrain Forward-most portion of the brainstem

The midbrain or mesencephalon is the forward-most portion of the brainstem and is associated with vision, hearing, motor control, sleep and wakefulness, arousal (alertness), and temperature regulation. The name comes from the Greek mesos, "middle", and enkephalos, "brain".

The control of ventilation refers to the physiological mechanisms involved in the control of breathing, which is the movement of air into and out of the lungs. Ventilation facilitates respiration. Respiration refers to the utilization of oxygen and balancing of carbon dioxide by the body as a whole, or by individual cells in cellular respiration.

Reticular formation Spinal trigeminal nucleus

The reticular formation is a set of interconnected nuclei that are located throughout the brainstem. 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 pedunculopontine nucleus (PPN) or pedunculopontine tegmental nucleus is a collection of neurons located in the upper pons in the brainstem. It lies caudal to the substantia nigra and adjacent to the superior cerebellar peduncle. It has two divisions of subnuclei; the pars compacta containing mainly cholinergic neurons, and the pars dissipata containing mainly glutamatergic neurons and some non-cholinergic neurons. The pedunculopontine nucleus is one of the main components of the reticular activating system. It was first described in 1909 by Louis Jacobsohn-Lask, a German neuroanatomist.

Cranial nerve nucleus

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.

Anterior inferior cerebellar artery

The anterior inferior cerebellar artery (AICA) is one of three pairs of arteries that supplies blood to the cerebellum.

Facial motor nucleus

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.

Vestibular nuclei

The vestibular nuclei (VN) are the cranial nuclei for the vestibular nerve located in the brainstem.

Trigeminal nerve nuclei

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.

Lateral hypothalamus

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.

Fovilles syndrome Medical condition

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 vascular disease or tumors involving the dorsal pons.

Respiratory center Brain region controlling respiration

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 centre and the apneustic centre.

Salivatory nuclei

The salivatory nuclei are the superior salivatory nucleus, and the inferior salivatory nucleus that innervate the salivary glands. They are located in the pontine tegmentum in the brainstem. They both are examples of cranial nerve nuclei.

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

References

  1. ↑ Alheid, GF; Milsom, WK; McCrimmon, DR (2004). "Pontine influences on breathing: an overview". Respiratory Physiology & Neurobiology. 143 (2–3): 105–114. doi:10.1016/j.resp.2004.06.016. PMID   15519548. S2CID   32801207.
  2. ↑ Woolf, NJ; Butcher, LL (2011). "Cholinergic systems mediate action from movement to higher consciousness". Behavioural Brain Research. 221 (2): 488–98. doi:10.1016/j.bbr.2009.12.046. PMID   20060422. S2CID   9768708.
  3. 1 2 Tsang, EW; Hamani, C; Moro, E; Mazzella, F; Poon, YY; Lozano, AM; Chen, R (2010). "Involvement of the human pedunculopontine nucleus region in voluntary movements". Neurology. 75 (11): 950–9. doi:10.1212/WNL.0b013e3181f25b35. PMC   2942031 . PMID   20702790.
  4. 1 2 Tattersall, T. L.; et al. (2014). "Imagined gait modulates neuronal network dynamics in the human pedunculopontine nucleus" (PDF). Nature Neuroscience. 17 (3): 449–454. doi:10.1038/nn.3642. PMID   24487235. S2CID   405368.
  5. ↑ Mena-Segovia, Juan; Bolam, J. Paul; Martinez-Gonzalez, Cristina (2011). "Topographical Organization of the Pedunculopontine Nucleus". Frontiers in Neuroanatomy. 5: 22. doi: 10.3389/fnana.2011.00022 . PMC   3074429 . PMID   21503154.
  6. ↑ Braun, AR; Balkin, TJ; Carson, RE; Varga, M; Baldwin, P; Selbie, S; Belenky, P; Herscovitch, P (1997). "Regional cerebral blood flow throughout the sleep-wake cycle. An H2(15)O PET study". Brain. 120 (7): 1173–1197. doi: 10.1093/brain/120.7.1173 . PMID   9236630.
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