Function: this system keeps the organism awake & alert;
Projections from the brainstem and posterior hypothalamus throughout the forebrain.
Laterodorsal tegmental nuclei and pedunculopontine tegmental nuclei (LDT and PPT) send cholinergic fibers (Ach) to many forebrain targets, including the thalamus, which then regulate cortical activity.
Aminergic nuclei diffusely project throughout much of the forebrain. Regulating the activity of cortical and hypothalamic targets directly.
Neurons of the tuberomammillary nucleus (TMN) contain histamine (HIST), neurons of the raphe nuclei contain 5-HT and neurons of the locus coeruleus (LC) contain noradrenaline (NA)
interference /w proper function of RAS → Нарушение сознания
Impaired arousal states:
Drowsy
Delirium /Encephalopathy/ Confusional state (agitation)
Obtundation (falls asleep during evaluation)
Stupor (requiring stimuli to awaken)
Coma (not cognitively responsive)
Etiologies for RAS damage - In general bilateral damage is required to cause coma (structural Lesions)
Pons and Midbrain - stroke, bleed, compression, anoxia;
Bilateral Thalamic lesion - anoxia, trauma, bleed, stroke;
Bilateral acute cortical dysfunction injury - anoxia, seizures, trauma, medications.