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Reticular formation

Group 1: Reticular Formation Structure – Composed of almost 100 brain nuclei – Contains projections into forebrain, brainstem, and cerebellum – Includes reticular nuclei, reticulothalamic […]

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Group 1: Reticular Formation Structure

– Composed of almost 100 brain nuclei
– Contains projections into forebrain, brainstem, and cerebellum
– Includes reticular nuclei, reticulothalamic projection fibers, and ascending cholinergic projections
– Divided into raphe nuclei, gigantocellular nuclei, and parvocellular nuclei
– Contains two major neural subsystems: ascending reticular activating system and descending reticulospinal tracts

Group 2: Functions of Reticular Formation

– Consists of more than 100 small neural networks
– Functions include somatic motor control, cardiovascular control, pain modulation, sleep and consciousness, and habituation
– Relays eye and ear signals to cerebellum for motor coordination
– Plays a central role in states of consciousness like alertness and sleep

Group 3: Ascending Reticular Activating System (ARAS)

– Composed of neural circuits connecting midbrain and pons to cerebral cortex
– Contains more than 20 nuclei in upper brainstem, pons, medulla, and hypothalamus
– Neurons release dopamine, norepinephrine, serotonin, histamine, acetylcholine, and glutamate
– Important for consciousness, wakefulness, and EEG desynchronization
– Injury to ARAS can result in irreversible coma

Group 4: Descending Pathways and Reticulospinal Tracts

– Descending pathways to spinal cord via reticulospinal tracts involved in motor coordination and regulating exhalation
– Coordinate automatic movements of locomotion and posture
– Influence muscle tone, autonomic functions, pain impulses, and blood flow to the thalamus
– Reticulospinal tracts control sympathetic and parasympathetic outflows

Group 5: Clinical Significance and Developmental Influences

– Brainstem lesions can alter consciousness levels
– Lesions in specific nuclei associated with disorders like narcolepsy and Parkinson’s
– Preterm birth and smoking during pregnancy can impact ARAS development
– Damage to brainstem areas can lead to various motor dysfunctions and rigidity

Reticular formation (Wikipedia)

The reticular formation is a set of interconnected nuclei that are located in the brainstem, hypothalamus, and other regions. It 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.

Reticular formation
Coronal section of the pons, at its upper part. (Formatio reticularis labeled at left.)
Traverse section of the medulla oblongata at about the middle of the olive. (Formatio reticularis grisea and formatio reticularis alba labeled at left.)
Details
LocationBrainstem, hypothalamus and other regions
Identifiers
Latinformatio reticularis
MeSHD012154
NeuroNames1223
NeuroLex IDnlx_143558
TA98A14.1.00.021
A14.1.05.403
A14.1.06.327
TA25367
FMA77719
Anatomical terms of neuroanatomy

Neurons of the reticular formation, particularly those of the ascending reticular activating system, play a crucial role in maintaining behavioral arousal and consciousness. The overall functions of the reticular formation are modulatory and premotor, involving somatic motor control, cardiovascular control, pain modulation, sleep and consciousness, and habituation. The modulatory functions are primarily found in the rostral sector of the reticular formation and the premotor functions are localized in the neurons in more caudal regions.

The reticular formation is divided into three columns: raphe nuclei (median), gigantocellular reticular nuclei (medial zone), and parvocellular reticular nuclei (lateral zone). The raphe nuclei are the place of synthesis of the neurotransmitter serotonin, which plays an important role in mood regulation. The gigantocellular nuclei are involved in motor coordination. The parvocellular nuclei regulate exhalation.

The reticular formation is essential for governing some of the basic functions of higher organisms and is one of the phylogenetically oldest portions of the brain.[citation needed]


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