The gigantocellular reticular nucleus (also magnocellular reticular nucleus) is the (efferent/motor) medial zone of the

reticular formation The reticular formation is a set of interconnected nuclei in the brainstem that spans from the lower end of the medulla oblongata to the upper end of the midbrain. The neurons of the reticular formation make up a complex set of neural networks ...

of the caudal

pons The pons (from Latin , "bridge") 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 pons is also called the pons Varolii ("bridge of ...

and rostral

medulla oblongata 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 (involun ...

. It consists of a substantial number of giant

neuron A neuron (American English), neurone (British English), or nerve cell, is an membrane potential#Cell excitability, excitable cell (biology), cell that fires electric signals called action potentials across a neural network (biology), neural net ...

s, but also contains small and medium sized neurons. It gives rise to the lateral (medullary)

reticulospinal tract The reticular formation is a set of interconnected nuclei in the brainstem that spans from the lower end of the medulla oblongata to the upper end of the midbrain. The neurons of the reticular formation make up a complex set of neural networks i ...

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 periaqueductal gray (PAG), also known as the central gray, is a brain region that plays a critical role in autonomic function, motivated behavior and behavioural responses to threatening stimuli. PAG is also the primary control center for ...

, the

paraventricular hypothalamic nucleus The paraventricular nucleus (PVN) is a nucleus in the hypothalamus, located next to the third ventricle. Many of its neurons project to the posterior pituitary where they secrete oxytocin, and a smaller amount of vasopressin. Other secretions a ...

central nucleus of the amygdala The central nucleus of the amygdala (CeA or aCeN) is a nucleus within the amygdala. It serves as the major output nucleus of the amygdala and participates in receiving and processing pain information. CeA connects with brainstem areas that cont ...

, lateral hypothalamic area, and

parvocellular reticular nucleus The parvocellular reticular nucleus is part of the brain located dorsolateral to the caudal pontine reticular nucleus. The dorsal portion of the reticular nucleus has been shown to innervate the mesencephalic trigeminal nucleus and its surroundi ...

. It receives afferent corticoreticular fibers from the

premotor cortex The premotor cortex is an area of the motor cortex lying within the frontal lobe of the brain just anterior to the primary motor cortex. It occupies part of Brodmann's area 6. It has been studied mainly in primates, including monkeys and human ...

and

supplementary motor area The supplementary motor area (SMA) is a part of the motor cortex of primates that contributes to the control of movement. It is located on the midline surface of the hemisphere just in front of (anterior to) the primary motor cortex leg representa ...

which modulate the activity of reticulospinal and reticulobulbar efferents. It receives vestibular, visual, and auditory afferents to mediate head-eye movement coordination. It receives excitatory enkephalinergic afferents from the

which influence its descending pain-inhibiting efferents.

Function

Extrapyramidal motor functions

It gives rise to the lateral (medullary)

(which excites flexors and inhibits extensors of the muscles of the axial and proximal limbs). It is also involved in coordination of head-eye movements (receiving visual, vestibular, and auditory information to this end).

Blood pressure regulation

The GGRN forms part of the vasodepressor center which projects through the reticulobulbar tract to synapse upon pre-ganglionic

parasympathetic The parasympathetic nervous system (PSNS) is one of the three divisions of the autonomic nervous system, the others being the sympathetic nervous system and the enteric nervous system. The autonomic nervous system is responsible for regulat ...

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.

Respiration

GGRN induces inspiration (whereas the parvocellular nucleus causes

expiration Expiration or expiration date may refer to: Expiration Expiration may refer to: *Death *Exhalation of breath, breathing out * Expiration (options), the legal termination of an option to take an action *Shelf life, or the time after which a product ...

Descending pain-inhibiting pathway

The GGRN - together with the

nucleus raphe magnus 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 NRM receives afferent stimuli from the enkephalinergic neurons of the periaqueductal ...

- gives rise to the descending serotonergic

raphespinal tract 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 ...

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

References

It also receives inputs from the pedunculopontine nucleus. Medulla oblongata {{Neuroanatomy-stub