Learning objectives :
1.
To know the definition and the area where the reticular formation is present in the brain because it is diffused area occupying the brain.
2.
T o know the group of nuclei,
functions,
afferents and efferents because the RF is
almost have connections with various part of the brain.
3.
To know the nuclei group of the RF involved in various neurological and psychiatric disorders
Reticular formation is defined as diffuse as diffuse ill-defined mass of intermingled neurons & nerve fibres occupying the entire core of brainstem
Phylogentically it represents old reticular core of brain & contains vital cardiac & respiratory centers.
The importanc of RF :
· it regulates level of consciousness & alertness
· regulates respiration,
blood pressure,
heart rate
· regulates tone of skeletal muscles
· modulates the impulses in pain pathways
The reticular nuclei in brainstem arranged into three longitudinal columns:
1.
Median column : lies in midline,
termed as raphe nuclei & has three parts,
produces serotonin
a) dorsal raphe nucleus-projects to spinal cord forming pain controlling pathway
b) nucleus raphe pontis-
c) nuleus raphe magnus-projects to caudal part of sipnal nucleus of V cranial nerve & influences perception of pain
2.
Medial column termed as magnocellular column includes ventral reticular nucleus (in medulla ),
gigantocellularnucleus (in meulla & pons ),oral & cadual ponine nuclei (in pons ) receive afferents from lateral group & efferents ascend & descend in brain stem forming polysynaptic pathway
3.
Lateral column termed parvocellular column includes parvicellular nuclei of medulla & pons,
nucleus locus ceruleus of pons & pedunculopontine nucleus of midbrain
Connections of reticular formation:
Afferent connections : classified into three types :
Afferents from various sensory pathways or systems
-Optic system –through tectoreticular fibres
-Olfactory & limbic system-through descending pathways
-Auditory system- through tectoreticular fibres
-Gustatoty system
-Spinal pathways through spinoreticular fibres
-Trigeminal pathways
Afferents fibres from other parts of CNS
-Cerebellum mainly from contralateral fastigial nucleus
-Basal ganglia mainly from corpus striatum
Thalamus,
hypothalamus & subthalamus
Limbic system mainly from septal areas,
amygaloid nucleus & hippocampus
Cerebral cortex mainly from motor & sensory areas
Red nucleus,
substantia nigra & habenular nuclei