Gigantocellular reticular nucleus

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Gigantocellular reticular nucleus
Details
Identifiers
Latin nucleus reticularis gigantocellularis
NeuroNames 730
NeuroLex ID nlx_anat_1005001
TA98 A14.1.04.302
TA2 6028
FMA 72576
Anatomical terms of neuroanatomy

The gigantocellular reticular nucleus (also magnocellular reticular nucleus) is the (efferent/motor) medial zone of the reticular formation of the caudal pons and rostral medulla oblongata. It consists of a substantial number of giant neurons, but also contains small and medium sized neurons. [1]

Contents

It gives rise to the lateral (medullary) reticulospinal tract which influences muscle tone of limb and trunk muscles, is involved in coordination of head-eye movements, promotes parasympathetic reduction of heart rate to decrease blood pressure, induces inspiration, and participates in the descending pain-inhibiting pathway.

Anatomy

Afferents

It receives connections from the periaqueductal gray, the paraventricular hypothalamic nucleus, central nucleus of the amygdala, lateral hypothalamic area, and parvocellular reticular nucleus.[ citation needed ]

It receives afferent corticoreticular fibers from the premotor cortex and supplementary motor area which modulate the activity of reticulospinal and reticulobulbar efferents. [1]

It receives vestibular, visual, and auditory afferents to mediate head-eye movement coordination. [1]

It receives excitatory enkephalinergic afferents from the periaqueductal gray which influence its descending pain-inhibiting efferents. [1]

Function

Extrapyramidal motor functions

It gives rise to the lateral (medullary) reticulospinal tract (which excites flexors and inhibits extensors of the muscles of the axial and proximal limbs). [1]

It is also involved in coordination of head-eye movements (receiving visual, vestibular, and auditory information to this end). [1]

Blood pressure regulation

The GGRN forms part of the vasodepressor center which projects through the reticulobulbar tract to synapse upon pre-ganglionic parasympathetic neurons of the nucleus of vagus nerve. It acts to decrease blood pressure by decreasing heart chronotropy (rate) by increasing vagal parasympathetic outflow to the heart. [1]

Respiration

GGRN induces inspiration (whereas the parvocellular nucleus causes expiration). [1]

Descending pain-inhibiting pathway

The GGRN - together with the nucleus raphe magnus - gives rise to the descending serotonergic raphespinal tract which projects to the spinal cord to inhibit transmission of pain stimuli. The serotonergic analgesic component of the GGRN receives excitatory enkephalinergic afferents from the periaqueductal gray. [1]

Related Research Articles

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<span class="mw-page-title-main">Vestibulospinal tract</span> Neural tract in the central nervous system

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The nucleus raphe magnus (NRM) is one of the seven raphe nuclei. It is situated in the pons in the brainstem, just rostral to the nucleus raphe obscurus.

The oral pontine reticular nucleus, or rostral pontine reticular nucleus is one of the two components of the medial (efferent/motor) zone of the pontine reticular formation - the other being the caudal pontine reticular nucleus. The efferents of these two structures together give rise to the medial (pontine) reticulospinal tract. A population of their neurons together also form the paramedian pontine reticular formation which is involved in the coordination of horizontal conjugate eye movements in response to head movements.

The spinoreticular tract is a partially decussating (crossed-over) four-neuron sensory pathway of the central nervous system. The tract transmits slow nociceptive/pain information from the spinal cord to reticular formation which in turn relays the information to the thalamus via reticulothalamic fibers as well as to other parts of the brain. Most (85%) second-order axons arising from sensory C first-order fibers ascend in the spinoreticular tract - it is consequently responsible for transmitting "slow", dull, poorly-localised pain. By projecting to the reticular activating system (RAS), the tract also mediates arousal/alertness in response to noxious (harmful) stimuli. The tract is phylogenetically older than the spinothalamic ("neospinothalamic") tract.

The hypothalamospinal tract is an unmyelinated non-decussated descending nerve tract that arises in the hypothalamus and projects to the brainstem and spinal cord to synapse with pre-ganglionic autonomic neurons.

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The raphespinal tract is a descending spinal cord tract located in the medulla oblongata. It consists of two tracts an anterior raphespinal tract, and a lateral raphespinal tract that mainly descend in the lateral funiculus. Fibers descend in the ventral portion of the lateral funiculus, mainly bilaterally to terminate in laminae I, II, and IV.

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.

The interstitial nucleus of Cajal is a collection of neurons in the mesencephalon (midbrain) which are involved in integrating eye position-velocity information in order to coordinate head-eye movements - especially those related to vertical and torsional conjugate eye movements (gaze). It also mediates vertical gaze holding.

References

  1. 1 2 3 4 5 6 7 8 9 Patestas, Maria A.; Gartner, Leslie P. (2016). A Textbook of Neuroanatomy (2nd ed.). Hoboken, New Jersey: Wiley-Blackwell. pp. 224, 306, 309–311. ISBN   978-1-118-67746-9.

It also receives inputs from the pedunculopontine nucleus.