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The brainstem is the posterior part of the brain, continuous with the spinal cord. In the human brain the brainstem includes the midbrain, the pons and medulla oblongata of the hindbrain. The midbrain continues with the thalamus of the diencephalon through the tentorial notch, and sometimes the diencephalon is included in the brainstem.
The raphe nuclei are a moderate-size cluster of nuclei found in the brain stem. They have 5-HT1 receptors which are coupled with Gi/Go-protein-inhibiting adenyl cyclase. They function as autoreceptors in the brain and decrease the release of serotonin. The anxiolytic drug Buspirone acts as partial agonist against these receptors. Selective serotonin reuptake inhibitor (SSRI) antidepressants are believed to act in these nuclei, as well as at their targets.
The nucleus ambiguus is a group of large motor neurons, situated deep in the medullary reticular formation named by Jacob Clarke. The nucleus ambiguus contains the cell bodies of neurons that innervate the muscles of the soft palate, pharynx, and larynx which are associated with speech and swallowing. As well as motor neurons, the nucleus ambiguus contains preganglionic parasympathetic neurons which innervate postganglionic parasympathetic neurons in the heart.
The reticular formation is a set of interconnected nuclei that are located throughout the brainstem. The reticular formation 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 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.
In animals, including humans, the startle response is a largely unconscious defensive response to sudden or threatening stimuli, such as sudden noise or sharp movement, and is associated with negative affect. Usually the onset of the startle response is a startle reflex reaction. The startle reflex is a brainstem reflectory reaction (reflex) that serves to protect vulnerable parts, such as the back of the neck and the eyes (eyeblink) and facilitates escape from sudden stimuli. It is found across the lifespan of many species. A variety of responses may occur because of individual's emotional state, body posture, preparation for execution of a motor task, or other activities. The startle response is implicated in the formation of specific phobias.
The zona incerta is a horizontally elongated region of gray matter in the subthalamus below the thalamus. Its connections project extensively over the brain from the cerebral cortex down into the spinal cord.
The paramedian pontine reticular formation, also known as PPRF or paraabducens nucleus, is part of the pontine reticular formation, a brain region without clearly defined borders in the center of the pons. It is involved in the coordination of eye movements, particularly horizontal gaze and saccades.
The reticulotegmental nucleus, tegmental pontine reticular nucleus is an area within the floor of the midbrain. This area is known to affect the cerebellum with its axonal projections.
The parvocellular reticular nucleus is part of the brain located dorsolateral to the caudal pontine reticular nucleus.
The oral pontine reticular nucleus, or rostral pontine reticular nucleus, is delineated from the caudal pontine reticular nucleus. This nucleus tapers into the lower mesencephalic reticular formation and contains sporadic giant cells.
The gigantocellular nucleus is a subregion of the medullary reticular formation. As the name indicates, is mainly composed of the so-called giant neuronal cells.
The paramedian reticular nucleus sends its connections to the spinal cord in a mostly ipsilateral manner, although there is some decussation.
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.
Recurrent thalamo-cortical resonance is an observed phenomenon of oscillatory neural activity between the thalamus and various cortical regions of the brain. It is proposed by Rodolfo Llinas and others as a theory for the integration of sensory information into the whole of perception in the brain. Thalamocortical oscillation is proposed to be a mechanism of synchronization between different cortical regions of the brain, a process known as temporal binding. This is possible through the existence of thalamocortical networks, groupings of thalamic and cortical cells that exhibit oscillatory properties.
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.
Serotonergic cell groups refer to collections of neurons in the central nervous system that have been demonstrated by histochemical fluorescence to contain the neurotransmitter serotonin (5-hydroxytryptamine). Since they are for the most part localized to classical brainstem nuclei, particularly the raphe nuclei, they are more often referred to by the names of those nuclei than by the B1-9 nomenclature. These cells appear to be common across most mammals and have two main regions in which they develop; one forms in the mesencephlon and the rostral pons and the other in the medulla oblongata and the caudal pons.
The medial pontine reticular formation (MPRF) is a part of the human brain located in the pons of the brainstem. It plays a critical function in the generation of REM sleep.
In neuroanatomy, corticomesencephalic tract is a descending nerve tract that originates in the frontal eye field and terminate in the midbrain. Its fibers mediate conjugate eye movement.
References
- ↑ Sasaki S, The neural control of orienting: role of multiple-branching reticulospinal neurons. Prog Brain Res. 2004;143:383-9.
- ↑ Scott G, Effect of lidocaine and NMDA injections into the medial pontobulbar reticular formation on mastication evoked by cortical stimulation in anaesthetized rabbits. Eur J Neurosci. 2003 May;17(10):2156-62.
