Reticular formation

The reticular formation (RF) is a phylogenetically old network of interconnected neurons. It permeates the brainstem, continues into the thalamus and hypothalamus, and connects caudally to the propriospinal spinal network.

It begins as a band of grey matter in the cervical part of the spinal cord. A large portion are interneurons.

Functions:

-sensory, motor and autonomic function, complex reflexes

- control centre for respiration, cardiovascular system, vasomotor, sleep, wakefulness

- ARAS - ascending reticular activating system - maintenance of wakefulness, circadian cycle (24 hour)

- reticulospinal system - motor functions

3 main zones of nuclei: a) nuclei raphes b) medial region c) lateral region

Nuclei:


 * 1) At the midline of the pontus (nuclei raphe),
 * 2) lateral magnocellular RF (mostly efferent),
 * 3) at the border of the pontus and oblongata, gigantocellular RF + central reticular nucleus + parvocellular RF (mostly afferent) extending into the mesencephalon,
 * 4) in the oblongate nuclei paramedian (connecting the cerebellum) + lateral (connecting the cerebellum and spinal cord),


 * function: gigantocellular nucleus - standing + walking, nucleus in lat. pontus - bladder control, central nuclei of the oblongata - circulation + respiration

 Nuclei raphes 

- along the midline of the brainstem, different species - heterogeneous, produce neurotransmitters such as serotonin, GABA, glycine, neuropeptides, substance P, cholecystokinin

 Medial region of nuclei 

- source of efferent pathways - effector part

 Lateral region of nuclei 

- afferent fibres, sensory part

- of the spinal cord, rhombencephalon, cranial nerve nuclei, mesencephalon, cortex, basal nuclei

RF neurons produce:


 * serotonin - with a maximum in the ncl. raphe in the oblongata, pontus and mesencephalon,
 * dopamine - in the tegmentum of the mesencephalon,
 * noradrenaline - in the pontus - locus coeruleus + laterobasally in the wall of the IVth ventricle,
 * adrenaline in the oblongata,
 * aminergic neurons controlling sleep and wakefulness, attention and mood, with a close relationship to sensation,
 * serotonin + noradrenaline in depression, dopamine in schizophrenia.

Ascending reticular formation ARAS

 * receives all stimuli from all afferent sensory + sensory pathways (exteroreceptors, proprioceptors, receptors from internal organs),
 * connected to the cerebral cortex,
 * its constant activity ensures wakefulness (ARAS - the part of the RF that influences consciousness and wakefulness by its action on the cerebral cortex)
 * when disturbed, impaired consciousness (up to coma).

Descending RF

 * 1) Facilitatory RF - has constant activity, in the rostral region of the trunk,
 * 2) inhibitory RF - no spontaneous activity, controlled by cortex + basal ganglia,

Both of these parts are related to momentum, especially γ-motoneuron excitability.

Related articles

 * Cerebellum
 * Basal ganglia
 * Capsula interna
 * Impaired consciousness